DOVETAILING

DESCRIPTION

Figure 1

Dovetailing is a method of milling slots or channels that have angled side walls yield ing an opening that is wider at the bottom than at the top.  This type of groove is intended to hold a piece of material whose edges have been bevelled at an angle corresponding with those in the slot.  When  assembled, the mating piece is retained within the channel, but con be moved back and forth.

A good example of a dovetail application, is the master copy type and copy slide used on manual engraving machines.  The copy slide is a dovetailed channel and the type blanks have bevelled edges.  The type is retained in the slide, but can be moved easily for insertion and removal.

APPLICATION

A practical application for dovetailing in the engraving industry is the fabrication of directory signs that have removable in serts or legend plates.  Signs of this type are generally made using acrylic or flexible engraving stock and can be mode to be as decorative as they are useful.

When using acrylic, products that have both a clear and coloured layer, like the Romark Slickers, con be used to create a wide range of options and effects.  These

materials can be reverse engraved and then paint filled with contrasting colours.  Directories made from flexible engraving stock can incorporate inserts and back grounds of different colours and con be equally as attractive.

The main sign plate that has the dove tailed slots should be a minimum of 1/8″ thick. The insert strips are generally 1 1 / 6″ thick and are recessed the same thickness so that the face of the strip is flush with the surface of the sign.

TECHNIQUE

Creating the dovetailed slot is a milling operation that is done with a ‘dovetail’ cutter.  This cutter is ground with a nega tive angle that produces the undercut on the edge of the slot.  The insert strip is cut out using a profiling cutter that has an angle that matches that of the dovetail cutter. Neither procedure is particularly difficult once the basics are understood.

For the dovetailing operation, we first need to create a computer generated logo pattern or an engraving template that provides a series of parallel cutter passes (Figure 1). For purposes of example, let’s assume we are making a 1.5′wide slot and are using a 0.25 dovetail cutter.  Since the lines in our logo pattern define the centre of the cut – not the edge – we must subtract the cutter tip diameter from the finished slot width. In this case, 1.5″, less the cutter (.250′), equals a pattern width of 1.25″.

Since each cut is .250″ wide, there would be five passes required to create the full width of 1.25″ (1.25 divided by.250 = 5. It is desirable however to have one pass overlap the next, so the logo should be created with at least one more line than the number calculated. In the case of our example, there would be six lines rather than five.  This will eliminate any ridges in the bottom of the cut.

The dovetail cutter cuts wider at the bot tom than it does at the top, so the cut must be made at full depth.  The logo pattern should be made longer than the width of the plate so that the cutter can be low ered to the specified depth before it contacts the plate.  After it is lowered, the cutter enters the edge of the material, makes the pass, exits the other edge and repeats the process for the next pass, (Figure 2) It is important to remember that the cutter can only be raised when it is off the plate.

As there is a considerable amount of material being removed, the dovetailing process is slower than normal engraving.  As a rule-of-thumb, cutter speed should be about 10,000 rpm and the feed rate (the speed the cutter moves through the material) should be about 15 to 30 inches per minute depending on the material slower in acrylic, faster in flexible, A slot that is 1.5″ wide by 10″ long can easily be produced in 3 to 4 minutes.

When working in acrylic, it is strongly rec ommended that a water-soluble cutting oil be used.  It allows for better finishes, faster feed rates and extends cutter life.

With the dovetailing complete, the next step is to make the insert strips.  This is done with a ‘profiling’ cutter which is sharp ened at an angle that matches the angle on the groove.  Like the dovetailing op eration, a logo pattern must be created that will yield a plate of the proper length and width.  A simple rectangle is all that is needed, (Figure 3). As with the dovetail pattern, it is necessary to factor in the cutter tip size when making the calculations.  If we were making a strip that was 1.5″ x 1 0″ and were using a profiler with a .030″ tip, we would add .030″ to each dimension yielding a rectangle measuring 1.530″ by 10.030″. When mak ing the strips, we are concerned with the inside of the cut, so we add the cutter width rather than subtract it.

There are two methods of profiling, One is to tape the sheet of material to a scrap piece of plastic using double-faced mask ing tape and engrave completely through the top piece of material.  The strips are removed from the tape backing and are ready to use.

The other method is to clamp or tape the material to the machine table and en grave only partially through it, leaving a few thousandths of material to hold the plates in place.  The pieces are then snapped apart, however they must be trimmed to remove the thin web that was not completely removed during profiling.

The fit between the strips and the dove tailed channel should be close enough to hold the strip snugly, but not so tight that it binds when inserted or removed.  The fit can easily be adjusted by altering the width of the insert by adjusting the width of the rectangle pattern a few thousandths either way.

Figure 2

Jay Hoffpauir

I am often asked by people, in our industry how to engrave stainless steel with computerised machines. Often, these people have tried, quite unsuccessfully, to engrave stainless, and have done little more than ruin a lot of cutters and material.
The causes for this can be traced to, many things, including using the wrong cutters, wrong spindle speeds, wrong feed rates, wrong type of material, and misunderstanding the basic principles of the material involved.

The Engraving Machine:

Stainless is a very strange material with which to work. It is very hard but, depending on the type or grade of material, can be cut freely. The cutter has a hard time penetrating the surface of the stainless, then has an even harder time staying at the proper depth.
The cutter tends to “porpoise” in and out of the material, giving a ragged cut. This process is very hard on the cutter itself, often shattering the tip. This problem can be overcome by applying more down pressure to the spindle, forcing the cutter to remain at the same depth in the material.
How much down pressure is needed? That is hard to say. The diameter of the cutter – the actual cutting size of the tip – has a lot do with the amount of pressure required. The larger the cutter, the more pressure that is needed to keep the cutter in the material.
Many computerised engraving machines have an adjustable spring to the change the pressure on the spindle. These systems work so that the spindle is held up by the actuator, which can be either an air cylinder or a stepper motor. The spindle pressure is regulated by the spring, which holds the spindle down.
This type of arrangement is often called a “Floating” spindle and is great in most applications. The air cylinder or stepper motor has nothing to do with the amount of pressure applied to the work piece.
This helps greatly when the operator is using a nosecone on uneven material by allowing the spindle to ride over the high and low spots in the work piece. This is also good for diamond drag work because it prevents the dreaded diamond dimple syndrome in which the diamond hits the brass or aluminium hard enough to cause a dent or dimple in the material.
The problem I have run into is that many computerised engraving machines do not have the capability of applying enough pressure to the spindle, even at the maximum settings. There is simply not enough spring tension available to keep the cutter down in the stainless.

.Some engraving machines will allow the user to “pin” the spindle arm to the actuator arm. The Dahlgren System 2 is an example of this. Pinning actually allows the air cylinder or stepper motor to push the spindle down onto the work, adding its push to that of the spring. This should be done with care to prevent damage to any of the parts involved.

One of the major problems with stainless engraving is that the engraving machine is not rigid enough. Too much vibration causes the cutters to break. This can be traced to the way the machine is built. Most of the engraving machines we use are designed for plastic and diamond drag engraving, little if any lateral forces are involved.
Materials used in this type of engraving (plastic) are soft and the action of the cutter through the work piece places only a small load on the spindle and carriage. The carriage is the part that mounts the spindle and tracks left to on the machine – the “X” axis.

The problems with stainless – necessary strong down pressure for the spindle and the unique cutting qualities of the material – cause high lateral forces and vibrations in the spindle assembly. This causes the cutter to break even though the user has carefully set the feed rates and spindle motor
There is little you can do about this problem. The dynamics of the machine simply will not allow good engraving in stainless. The way the X, and Z axis are mounted and tracked contribute to this.

‘V’ Wheels:

Some engraving machines use “V” wheels mounted on the carriage and table. These move along a steel rod fixed to the base plate and bridge assemblies on the machine.
“V” wheels are actually roller bearings with a “V” groove cut around the outside surface, in the same position as the tread on a tire. They are mounted on standoffs, usually bolts which give clearance.
The problem with these ‘V’ wheels is that there is no solid surface mounting between the pieces. The inside ring and the outside shell of the wheel are supported by ball bearings and tend to have some slack in them even when new.
The rails on which the bearings ride are fairly small – usually ¼ inch – and must be very straight and parallel or the table will not move freely. These rods also must be perfectly horizontal to the base plate of the machine and the standoffs for the “V’ wheels must all be the same length in order for the table top of the machine to be level.
Another problem is that there is a very small amount of area of the “V wheel in contact with the steel rod at any one time, and this allows play in the moving part.
Some of these problems can be overcome if the machine manufacturer is working to very close tolerances, but most machines designed to do stainless engraving, or any heavy duty application for that matter, shy away from this arrangement. They generally use “Steel Ways” or preloaded recirculating ball bearings called Thompson Bearings. These are mounted in a carrier and ride on a steel shaft of large diameter.

Steel Ways, Thompson Bearings:

Steel Ways are basically two pieces of steel cut to very close tolerances One is mounted on the fixed piece – the base plate for example – and one is mounted on the moving piece – the table.
The ways are well lubricated and slide across each other. The amount of pressure one applies to the other can be regulated and very little, if any, slack is found in such an installation. This is the typical set-up for large milling machines.
These ways must be kept clean, well lubricated, and receive regular maintenance. They are also quite expensive, thus increasing the basic cost of the machine involved.
They are, however, probably the best method of moving a table and maintaining rigidity and flatness because of the large amount of surface area involved between the two pieces or steel. The optimum set-up calls for the steel to be case hardened and to have lubrication grooves cut into the face.
Thompson Bearings are actually many small ball bearings mounted in carrier, cylindrical in shape, several inches long and with a split down one side. These bearings recirculate through the carrier as it moves along the steel shaft.
The steel shaft is very straight (hopefully) and should be mounted parallel to the base plate. These bearings have the advantage of being fairly inexpensive, at least in comparison to the Steel Way described above, and can run dry. No lubrication is required.
The recirculating action of the bearing moves a large percentage or the ball bearings into contact with the steel shaft, increasing the amount of surface area. Increased surface area translates into more rigidity for the moving parts. These bearings can be fitted to a variety of shaft sizes, one-half inch or larger being the norm.

Pre-loading:

The term ‘pre-load” means that the amount of pressure the ball bearings apply to the steel shaft may be regulated by set screws that press the carrier closer to the steel shaft. This method is used on many of the ‘heavy duty” engraving machines on the market.
The mounting of the spindle must be rigid as well. Heavy duty engraving machines often use a steel spindle, very straight and polished, riding in a bronze oil-impregnated bushing.
The bushing is honed to a very close tolerance, usually within several thousandths of an inch, to match the spindle. This method offers a great deal of surface area and thus gives a very rigid but free moving mount.
Many of the engraving machines we use for plastic and diamond drag engraving use a “ball slide”. This slide comprises two blocks of aluminium separated by a series of small ball bearings.
These bearings may be pre-loaded to give a free movement, but the pre-load is set by up to six set screws and great care must be taken to keep from applying to much pressure at any one spot.
The problems with the ball slide is that wear causes the slide to have slack and they must be kept very clean. Also, the amount of surface area available is small so vibrations can build up. If you apply enough pre-load to take out the shack, the ball slide will slick and not move freely.
So, if you get my point, the type of machine used has a lot to do with whether you can engrave stainless steel without ruining your cutters. Your $6,000 computerised engraving machine (how old is this article?) was designed to do plastic and diamond drag engraving not stainless steel.

Spindle:

Most of the engraving machines available use top-loading cutters. These cutters slide though the spindle and are held in place by the threaded knob on the top. The shaft that the cutter slides though must have enough clearance to allow the cutter to slide freely in and out of the spindle,

The only holding point is at the top. This is fine for plastic engraving and burnishing, and is the generally accepted method for holding cutters for light duty machines. The very nature of the spindle allows the cutter to wobble or vibrate at the bottom or the spindle, the most critical point. This causes the cutter to break when used with hard materials such as stainless steel.

The best method of holding a cutter is considered to be a “collet” spindle. A collet fits into the bottom of the spindle and has a taper on the outside. This taper is matched in reverse on the inside of the spindle.

The collet has threads on the non-tapered end and is mated to a draw bar that is inserted through the top of the spindle. The collet usually has three splits or cuts along the taper.

The action of tightening the draw bar pulls the collet up into the tapered part of the spindle, compressing the collet around the cutter. This action causes the cutter to be held lightly at the point where it is needed most, at the bottom of the spindle close to the cutting tip.

Some spindles can use both the normal, top-loaded cutters we see everyday as well as short, one-and-one-half to two inch cutters. The short cutters are generally considered to be better for heavy duty work because there is less chance the cutter will be bent, and there is less weight involved. This should tell you that if you do not have a collet type spindle, your chances of engraving in stainless without breaking a cutter are low.

Cutters:

The cutter you use to engrave stainless steel should be ground to a different angle than the one you use for plastic. In general, different angles should be used for different materials. Plastic engraving stock, phenolic, brass, aluminium, steel, stainless steel, etc., all should have a cutter ground to match the properties or the material.

Because of the hardness of the material involved, cutters ground for stainless need more strength in the tip. This is achieved by utilizing a much larger included angle than normally used for plastic. These cutters should have around an 80 degree included angle.
This can be described by looking a the back of the cutter, with a 40 degree angle going from the tip, up to the shank of the cutter on both sides. A standard plastic cutter uses around a 60 degree included angle.
The 80 degree angle gives the cutter more strength. The clearance angle for the cutter is also different. A plastic cutter uses around a 45 degree clearance. A cutter ground for stainless uses a 25 to 30 degree clearance. I recommend a good grade of carbide for the cutters, although I know many people who swear by high speed steel.
Two good cutters for stainless are quarter round solid carbide and quarter round solid carbide Titanium coated.

Coolant:

A good grade of cutting oil can prolong your cutter’s life. By cutting oil I don’t mean 3-in-1 oil or WD-40. Cutting oil is specially formulated to use cutting applications and won’t break down like the other oils mentioned (use CESCO Green Lube). The idea of the oil is not to act as a lubricant but to help keep the cutter cool. See our article on the cooling tub.

Methods, speeds, and types:

There are many different grades or types of stainless steel. Some harder than others. Some have more nickel than others. The most common grade used in my shop is called “304”. This material is softer than a grade such as “316” but harder than “302”. We do a lot of engraving in this material and find it will satisfy most of our customers’ demands.
Another common problem is created by trying to engrave to the depth needed in three or four passes. The action of the cutter through the material heats the stainless. This actually heat treats the material, making it even harder than it was before!
Every pass hardens the material to a higher Rockwell number and finally makes it nearly impossible to cut. The preferred method is to try to take full cut in one pass, with a clean up pass to remove any burrs done at the same depth.
The engraving machine should be set to as slow a feed rate as possible for this. This type of engraving should be done without a nosecone. Stainless will scratch and mar the finish of a nosecone.
So what have we learned here? To review, all you have to do to engrave stainless steel on your computerised engraving machine successfully is:

• Engrave at a slow feed rate ( the slower the better)
• Engrave without a nosecone
• Engrave using a good cooling lube
• Engrave using a low spindle rotating speed
• Engrave using the right relief and included angle grind on a solid carbide cutter
• Engrave using a rigid engraving machine with a collet loaded spindle set in a solid block that has enough spring pressure to keep the cutter down in the material.

© Copyright 2003 by Awardline.com

The Supporting Cast
Adhesives, Oxidizers and Polishers

The most recognisable products in an engraver’s shop include brass plates, wood plaques, trophy parts and plastic engraving stock. Without these products, engravers wouldn’t be able to fill customer orders or make a living. But there are other products that are just as important to an engraver but don’t get as much attention; as the so-called supporting cast.
This cast consists of adhesives, oxidizers and polisher/cleaners. Every now and then, it’s a good idea to take a closer look at these products and familiarise yourself with their uses and any improvements to make them better. Experts offer tips on usage and safety and by paying attention to their advice, you can make your shop safer and make the engraving jobs easier to perform. The result: a finished product that your customer will appreciate and you’ll be proud to sell.
Let’s take a look at some of the most common support products and their uses in your shop:

Adhesives
The most common materials in an engraver’s shop are often bonded together to form badges, signage and plaque plates. Plastic and metal are composed of chemical properties, making it important to know which works best with compatible adhesives.
“Engravers can use the wrong adhesives and not be aware of it,” says Karen Coppes of Laminated Fabricators, Inc. “They wind up being unhappy with the job. It’s important to know how adhesives are used.”
Coppes says that one of the most common adhesives for bonding plastics together is brown cement (Stock #99126). It comes in a 5-ounce tube, and is especially formulated for working with phenolic material. Her company also sells a clear cement (Stock #99125) in a 5-ounce tube which bonds plastic to metal.
Another adhesive that works well for bonding plastic to metal is Engravers ExpressBond, Distributed by Engravers Express. Engravers ExpressBond is a nonsolvent based formula that bonds in 10 seconds. According to Engravers Express, Engravers ExpressBond takes the place of Liquid Bond, which was found to environmentally unsafe. Engravers ExpressBond is a relatively new product to the market, having been introduced about a year ago.
The choice for adhesives can be a personal preference. Johnson Plastics Inc. sells two types of adhesives that perform the same duty – bonding plastic to metal. Choice No. 1 is Scott Cement Bond 14, which comes in a 4-ounce bottle. It can be used for bonding plastic to plastic as well. Bond 14 takes 24 hours to cure and is not recommended for mounting signs.
The second choice is Bond Adhesive #634, which comes in a 3.2 ounce tube. It can be used to bond plastic to plastic, fibreglass, fabric, metal and polystyrene. It can also be used to bond metal to metal.
Margaret Johnson of Johnson Plastics Inc. says that most people use these types of adhesives for bonding metal badge findings to plastic name badges.
She also recommends another adhesive to use when bonding plastic to plastic, called Rez-N-Bond #1. Rez-N-Bond #1 is a fast drying, clear liquid solvent. It is available in a one quart can or a 2-ounce applicator bottle with a needle nose.
“Rez-N-Bond actually melts the two pieces of plastic together to form a single surface,” says Johnson. “We don’t recommend using this to bond plastic to metal. We also suggest that this adhesive be applied carefully. Excess adhesive can actually eat away at the plastic surface.”
Chris Black of Wholesale Trophies, Inc. borrows a phrase from a popular 1960′s television commercial. “Use the ‘little-dab-will-do-you’ application because sometimes these cements become more permanent than the end user actually desires,” he says.
Johnson also recommends watching manufacturer’s application directions and read all of the cautions. As with any other cleaning or adhesive material, it should be applied in a well-ventilated area.
Another type of adhesive that is very popular for working with uneven surfaces is Urethane Bond, manufactured by Dow Chemical. According to Don Marnella of Jonko Products, Inc., this adhesive comes pre-mixed in a tube and has many uses. “Some of these uses are still undiscovered by many dealers,” adds Marnella. “It is equal in strength to two part epoxy, without mixing requirements.
“The product expands to fit uneven surfaces in order to glue to a smooth surface.” He cites one example of a national company that reproduces children’s hand prints or footprints in plastic or ceramic. “The print is mounted on a marble base and Urethane Bond is used to adhere it. This is the only adhesive that we have found which successfully bonds.” Excess glue from the uneven surface can be trimmed with a utility knife after it cures.
Not all adhesives come in glue form. One of the more popular methods that involves less mess is the adhesive tape method. Some engravers avoid the cementing process and opt for double-sided tape. One manufacturer says that tape is all he would ever use to bond.
Jerry Copeland of American Trophy, Awards & Engraving swears by a product called Tesa-Tape. “It is yellowish, double-sided tape made of an acrylic adhesive,” he says. “It is so strong that you better get the alignment right the first time.”
Don Marnella of Jonko Products offers some advice for using his company’s Double Face Tape #492. “It is imperative that surfaces be clean, free from oil and chemicals. The ideal application temperature is between 70 and 1 00 degrees. Always burnish the tape down with considerable pressure.”
Marnella says that acrylic tape is one of the best ways to assure a permanent bond, especially due to variations in temperatures.
“Consider an award sitting in the trunk of a car where the temperature may be between 150 and 200 degrees. Both rubber adhesive and acrylic adhesive will soften with exposure to heat but at different large quantities. A two-ounce jar can be shipped by air, but a gallon jug would have to be transported by ground. Black says that customers should be aware of this regulation and the additional time and expense it takes for shipping large quantities.
Margaret Johnson offers some advice on using liquid oxidizers. “We recommend that our customers pour a little of the liquid into a cap. The entire jar can be contaminated if left open. Use a Q-tip to apply, but don’t reuse it after the initial application. People sometimes complain about the ineffectiveness of an oxidizer because they have let it become contaminated, which reduces its effectiveness.”
Also remember that natural oxidization occurs immediately after an engraved character is exposed to air. To achieve maximum darkening of letters, it is important to apply the oxidizer immediately after the character is engraved. Oxidizers and natural oxidization do not always team up to make the best results, which is an effective darkened character Another way to assure an effective darkened engraved character is to ensure that the engraving cutter is sharpened and has no jagged edges. “Any small burrs or uneven lines will be accentuated by an oxidizer,” Johnson says.
Jerry Copeland suggests ways to maximize the oxidization process. “First, use a diamond burnisher to add depth to the character and to hold the oxidizer. Apply the oxidizer and then dab off the excess. I wait five to six hours and dab some more oxidizer on. I then let it sit overnight and clean it up with Pledge the next day.”

Cleaners and Polishers

Like Oxidizers and adhesives, there are different cleaners/polishers to choose from, depending on the product surfaces.
Ken Petersen Sr. of Petersen Brothers says that a lot of people may not know how to deal with scratches and cleaning surfaces. That is one of the reasons why his company supplies a leaflet with all Novus cleaning products it sells. The leaflet points out basics of preparing surfaces, cleaning, removing scratches and polishing.
The Novus products highlighted in the leaflet are Novus No. 1, which is used clean plastics without scratching. It leaves a shine that resists fogging, repels dust and eliminates static. Novus No. 2 removes fine scratches and abrasions from most plastics and can eventually restore faded and discolored plastics.
Petersen strongly believes in the importance of cleaners and polishers, so much, in fact that he is taking them on the road with him.
“We will feature some of the Novus products at an upcoming show. We want people to know how to clean scratches,” he adds. “We’ve been at shows where people have told us that they use toothpaste and a brush to fill a crack. But it didn’t seem to take the whole scratch out.”
Jonko Products offers a cleaner polish that is very similar to the ones found in the home. Panel-Nu is a spray-on, wipe-off cleaner polish. “It is not unlike lemon oil, which can be purchased at the store,” says Don Marnella. “It works as well on plaques as it does on kitchen cabinets. It can also handle minor scratches very well.”

Another cleaner polisher sold by both Laminated Fabricators and Wholesale Trophies is Award Glow. It is a non-abrasive, citrus based polish, cleaner, anti-oxidant and protectant for most metals and acrylics. According to Chris Black Of Wholesale Trophies, the product will work with almost any surface. The list includes brass, aluminium, stainless steel, chrome, acrylic, fibreglass, plastic, silver, silver plate, glass and mirrors.
“Just rub it on, wait for it to dry to a base, then rub with a soft, clean cloth,” Black says.
The citrus base assures no oily residue and complete evaporation. It also assures something else. “it is a cleaner and healthier way to Polish because of the citrus base,” says Karen Coppes of Laminated Fabricators. She also said that Award-Glow works well on new Victory Laser-Brite products.
The variety of adhesives, oxidizers, and cleaner/polishers make the engraver’s job a little easier. Although these products are sometimes taken for ranted, they can make the difference between a quality finished product and a so-so one.
Suppliers want engravers to know how to use their products and what precautions to take when using them. Safety during the engraving and assembly process is just as important as quality – which is very important to the end user.

© Copyright 2003 by Awardline.com

ROTARY ENGRAVING

DESCRIPTION

Rotary engraving is the term used to describe engraving done with a rotating cutting tool in a motorized spindle.  The tool, or cutter, cuts into the surface of the material to a predetermined depth and produces a groove of the same shape and dimension of the cutter.  Rotary engraving can be performed on a wide variety of materials with plastic, brass and aluminum being the most common in the awards and engraving industry.

Figure 1

Rotary engraving can be done using the simplest pantographs to the most complex computerized engraving machines.  The principles are the same on all.  On a pantograph, the operator lowers the cutter into the material and then forms the character by tracing a master (copy type, template, etc.) On a computerized machine, the cutter spindle (Z-axis) is lowered mechanically and then is moved laterally (X-axis / Y-axis) by stepper motors to form the characters.

ENGRAVING CUTTERS

The tools used for rotary engraving are generally referred to as ‘cutters’.  Cutters are manufactured from different materials and are produced in a variety of configurations for specific applications and materials.  Most engraving cutters are ‘half round’ tools which means that a full round blank is split or halved on center producing a ‘single-lip’ tool which is one having only one cutting edge.  This configuration affords a significant amount of clearance and allows the tool to run at relatively high speeds to maximize material removal and produce good finishes.  Some cutters are made as ‘quarter-round’ tools which allows even greater clearance, but they are inherently weaker and are recommended for specific applications.

The majority of the engraving machines used in the awards and engraving industry have spindles that use ‘top-loading’ cutters.  These are cutters that are inserted into the spindle from the top and are typically held in place by means of a threaded knob. This arrangement allows for easy cutter changes and adjustments.  Top-loading cutters are most commonly available in 1/8″, 11/64″, 1/4″, 4mm and 6mm shank diameters and in a variety of lengths to accommodate machine spindles and accessories (burnishing attachments, vacuum chip

pumps).

Some machines, particularly industrial ones, utilize collet spindles.  The cutter is inserted into the top or the bottom (usually the bottom) of the spindle and is held in place by a collet which is a segmented, clamping device somewhat on the order of a drill chuck.  By means of a ‘drawbar’, the collet segments are tightened against the shank of the tool holding it securely in place.  This arrangement is more rigid and precise than the top-loading spindle, but does not offer the ease of cutter change and adjustment.

Most engraving cutters are manufactured from carbide or high speed steel (HSS). Carbide is an extremely hard and abrasion resistant material and is recommended for the majority of engraving cutter applications due to its toughness and long life characteristics.

Cutters manufactured from high speed steel do not have the hardness or the toughness and, therefore, become dull more quickly than those made of carbide.  They are not as brittle, however, and tend to be the best choice when making deep, fine cuts in metal as in the engraving of seal dies and the like.

CUTTER GEOMETRY

The various angles on a cutter are referred to as its geometry.  Each plays an important part in how well a cutter performs in a particular application.

The CLEARANCE ANGLE refers to the angle of the cutting edge with respect to the face of the cutter.  This angle allows for chip clearance, determines how fine the cutting edge is and is selected based on material properties. Generally, cutters for soft materials have greater clearance than those for hard materials.  Most cutters fall into one of four Engravers Express clearance categories:        FLX (soft plastics, i.e. flexible engraving stock); PHN (rigid plastic, i.e. phenolic); BAIL (softer metals, i.e. brass and aluminum) and SSS (harder metals, i.e. steel, stainless steel)

A cutter for flexible engraving stock has a high degree of clearance and a correspondingly fine edge.  If this cutter were used to engrave hard steel, its edge would be ruined rather quickly.  Conversely, a cutter sharpened with less clearance for harder materials will not produce as clean a cut in soft ones.

The CUTTING ANGLE is the angle formed between the cutter’s axis of rotation and its cutting edge and determines the shape of the cut.  Higher angles produce stronger tools and broader cuts and are recommended for hard materials.  Tools with lesser cutting angles are weaker, but are best for fine work in softer materials.

The TIP-OFF is the flat at the tip of the cutter which determines the width of the cut.  Since an engraving cutter needs to be .end-cutting’ as well as ‘side-cutting’, the cutter tip is actually a cutting edge.  It is formed by two angles that provide clearance and are selected based on the material being engraved.  Tip width is most correctly defined as being the width produced at the bottom of the cut.

Cutter width is selected based on character height and font style, As a rule of thumb, single stroke characters should have a width that is approximately 12% of the character height.  As an example, a half inch (.500′) letter should have a width of .060″(.500″X.12=.060′). lt. may be desirable to decrease width with condensed fonts and increase it on extended ones.  On multiple line fonts, the cutter width should be such that there is a slight overlap on each pass.

In addition to the various angles, the finishes on the cutting surfaces are very important in terms of the quality of the cut and how well a cutter holds up.  A grinding wheel contains abrasive particles (grit) that act like miniature cutting tools and produce a series of grooves in the surface of the part.  The finer the wheel, the smaller the grooves and the better the finish.

The cutting edge on an engraving cutter is the junction of the face and the back of the cutter.  If either of these surfaces have grind marks produced by coarse grits or improper grinding procedures, the result will be a cutting edge that is irregular and serrated.  Depending upon the severity of the condition, it can lead to rough and burred cuts with poor surface finishes.  Additionally, each serration is a fragile point that can quickly dull or break off further exaggerating the problem.  Engravers Express Micro-edge cutters are manufactured with extremely fine finishes that allow for optimum performance and tool life.

During the engraving process, the cutter rotates and moves forward through the material.  The actual cutting is produced by a shearing action between the cutter and the material.  As the cutter moves forward, the cutting edge engages the material, meets with resistance and shears or slices off a small piece of the material.

SPEEDS AND FEEDS

The cutter rotation is referred to as the cutting speed and the lateral movement is the feed rate.  Each has a pronounced effect on the quality of the finished cut.  The cutting speed is actually the measure of the distance traveled in surface feet per minute (sfpm) by the cutting edge and varies proportionately with the tip size.  For example, an.030″ cutter turning at I 0,000 rpm has a speed of approximately 75 sfpm while an .060″ cutter rotating at the same speed generates about 150 sfpm.  It is obvious then, that small cutters need to turn faster to achieve the same results as larger ones and vice versa.  Cutter speed is determined primarily by the material being engraved and the following table and graph can serve as a useful guide.

Feed rate should be proportionate to cutter speed and is dictated by material properties, horsepower and torque.  At a given cutter speed, a slow feed will produce more, smaller cuts and finer finishes.  A higher feed will produce fewer, larger cuts and rougher finishes.  Due to its single-lip design, an engraving cutter makes an ‘interrupted cut’ which means the cutting edge is not continually engaged in the material.  At each rotation, the cutting edge hits the material as it starts the cut.  On hard materials, the shock created by this intermittent action can damage the cutter and quickly destroy its edge, therefore dictating slower feeds.

While the above situation is not nearly as dramatic on softer materials, a cutter still needs time to cut.  Too high of a feed rate tends to cause the cutter to tear the material rather than cut cleanly resulting in rough, burred cuts. As a rule-of-thumb, the feed rate should be adjusted to allow maximum engraving speed without sacrificing quality of the finished cut.

One problem inherent to many machines common to the awards and engraving industry is their lack of power and torque at low speeds.  If the cutter speed is reduced appropriately for hard materials, there is insufficient power to produce the force required to make a good cut.  Engraving machines are not milling machines and care should be taken not to exceed machine capabilities,

CUTTING FLUIDS

Many of the materials common to the awards and engraving industry can be cut effectively without the use of cutting oils or lubricants.  Flexible engraving stock, phenolic, engravers brass and aluminum all fall into this category.  There are many other materials, however, that must be cut with a cutting fluid to achieve satisfactory results and reasonable cutter life.  Cutting fluids keep the cutter cool and prevent chips from adhering to the cutting edge.

The subject of cutting oils is very specific and complex, but the following are generalizations that may be helpful in a broad sense.

All steels should be engraved using an appropriate cutting fluid to improve the cut and extend tool life.  Soft aluminum that is not ‘free-machining’ can usually be engraved effectively using kerosene or a tapping fluid specifically formulated for aluminum.  Plastics that tend to melt when engraved can often be engraved with the use of water soluble cutting oil.  Engraving acrylic is a good example of this.

The use of cutting fluids even on materials that can be cut dry will often improve the finish of the cut and extend tool life.

ENGRAVERS EXPRESS has a complete line of diamond gravers, rotating diamonds, burnishers and rotary cutters for all popular engraving machines to meet all your needs and applications

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Burnishing Article

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DESCRIPTION

Burnishing is a method of rotary engraving on metals that tends to bridge the gap between diamond drag (scratch engraving) and routing. The biggest advantage of burnishing is that it enables the engraver to produce wider line widths than are obtainable with a diamond graver without having to rout or cut deeply into the metal. It is a surface marking technique intended for coated metals – usually lacquered brass where the coating is removed thereby exposing the bare metal, Burnishers can be used with single and multiple line fonts, and are an excellent tool for producing detailed line and logo work on metal. Burnishing offers the ability to create enhanced effects on both lettering and graphics and is relatively easy to master.

APPLICATION

The most common application for burnishing is on the brass plates on trophies and plaques. This ‘trophy brass’, as it is commonly known, is a hard material that offers excellent burnishing results. It’s available in various gold tones with a clear lacquer coating or in a variety of colours. When burnishing the gold material, the lacquer is removed exposing the bare metal. The burnished areas can then be oxidized or blackened and the result is a gold plate with
contrasting black letters. When burnishing the coloured materials, the result is a coloured plate with contrasting gold letters and no further treatment of the burnishing is necessary.

Burnishing can also be done on materials other than brass, however much of the success or failure lies in the hardness of the material *. Since burnishing is a surface technique, it is critical that the tip of the burnishing tool does not penetrate the surface of the material by an appreciable amount. Hard metals tend to prevent deep penetration of the burnisher and the tool works on the surface as it was designed. On softer metals, however, the tool is able to penetrate deeper which yields ragged edges on the burnished character and generally unacceptable results. Many of the coloured aluminium products on the market fall into this category and are not optimum choices for burnishing. There are harder aluminium products available with clear or black anodize treatments that can be effectively burnished.
It is also possible to burnish metals such as steel and stainless steel. Since the burnishing tool produces a swirled pattern, the mark is visible and may be suitable for some marking applications not requiring a sharp, well defined character. Generally speaking, however, these metals do not have coatings and, therefore, the burnishing cannot be blackened to add contrast.
BURNISHING TOOLS

The tool used for burnishing is called a ‘burnisher’ which is a rotating tool that is used in a motorized spindle. It is usually a carbide or carbide-tipped tool that is ground with four facets. Two of the facets form an angled chisel edge on the centre of the tool which is responsible for the actual burnishing or ‘scraping’ action. The other two facets are ground perpendicular to the chisel edge, equidistant from the centre of the tool and determine the width of the tip. Burnishers can also be made as diamond-tipped tools similar to those used in glass engraving. These tools produce a more brilliant mark, but are considerably more expensive. Cesco’s carbide burnishers are available in widths from .005″ up to the full diameter of the tool in increments of .005″, i.e. .005″, .010″, .015″, etc. When selecting tip size, you should follow the some guide lines that are used for other types of cutters. For example, if you were to use a .030″ cutter when engraving plastic, you would use a .030″ burnisher when burnishing a brass plate using the same font and letter size.

For those just getting started in burnishing, we recommend starting with three basic tip sizes of .015″ .020” and .030”. These will handle the majority of the small, single stroke characters commonly used on trophy plates and many of the multiple line, decorative fonts used on plaques and the like.

Burnishers are quite durable and are capable of producing thousands of characters. They do become dull, however, and require periodic resharpening. As a burnisher dulls, the chisel-edge becomes rounded. This produces rough edges and, if allowed to progress, will result in the surface colour being smeared into the burnished stroke, The latter condition can severely hamper oxidizing. Resharpening restores the edge to its original condition and costs the same as resharpening a standard engraving cutter.

TECHNIQUE

Since the purpose of burnishing is to remove the coating from the surface of the material, the key to achieving successful results lies in the amount of downward pressure that is exerted on the tool. A burnishing tool is not a cutter and if too much pressure is applied, the tool will be forced into the surface of the metal and the result will be a rough, ragged stroke. Ideally, the tip of the tool should float over the surface with only enough pressure to remove the coating without digging into the metal.

To set your machine for burnishing, remove the depth nose and insert the burnisher into the spindle. If the depth nose on your machine is large enough, you may leave it on and adjust the burnisher so that it extends beyond the bottom of the nose. In any case, the depth nose is not used in the burnishing operation and your set-up should prevent the nose from coming in contact with the surface of the material.

The next step is to lower the spindle to its full down position and set the burnisher. Loosen the set screw in the knob and lower the tool so that its tip firmly contacts the plate and then tighten the screw, Since the bases and tables of all machines are not perfectly level, it is important to set the tool at the lowest point on the plate. This will ensure that the tip of the tool will make contact over the entire surface. On computerized machines where the z-axis (spindle up-down) is controlled by air and or spring pressure, both should be set to their lowest setting. The motor speed should be relatively fast and the engraving speed should be at about the middle of it’s range. A slower engraving speed will produce a smoother finish in the burnished stroke.
The set-up procedure is identical for both pantographs and computerized engraving machines. On a pantograph, however, the correct pressure is determined by the ‘touch’ of the operator. It’s a technique that is easy to develop and the results should be equally as good as those achieved on a computer. One trick that some pantograph operators use is to remove or disable the spindle return spring. This allows the spindle to drop on its own and float over the material. The weight of the spindle clone is sufficient to produce the desired results, but you must remember to lift the spindle when going from character to character.

One way to simplify the burnishing operation and achieve consistent results is through the use of a spring-loaded burnishing attachment. These devices are used in place of the conventional knob and have an internal spring that applies the correct amount of pressure. These attachments usually require a burnisher that is longer than normal, so be sure to specify that you are using one of these attachments so that you get the proper length tool.

Compiled from an article by Antares Inc.

* To blacken brass use Brass oxidant. For oxidizing aluminium use aluminium oxidant.

* For burnishing aluminium or glass and even brass we recommend the use of diamond burnishers. These burnishers will give a longer life and provide a better cut.

Index Of Selected Cutters

Before talking about specific cutters it is first important to talk about what cutters are made of. The two most common cutters are high speed steel (HSS) and Micrograin carbide. Each of these cutters have different characteristics, and thus suggested applications for a particular engraving job. There are generally three characteristics that cutters are judged on: hardness, toughness, and abrasion resistance. Hardness usually means the ability of a cutter to resist fracturing during engraving. Toughness refers to the cutters resistance to stress and breakage. Abrasion resistance refers to the cutters wear due to friction.

High Speed Steel - high speed steel cutters are made of a steel alloy which contains a small amount of manganese which gives the cutter a high degree of hardness. This cutter will resist stress and breakage under heavy loads. These cutters are used primarily for engraving stainless steel and aluminum. However because this cutter is low in abrasion resistance when cutting into phenolic a HSS cutter will dull very quickly. Because of the overall ability of Micrograin carbide to engrave a variety of materials HSS cutters are only available in a half round conical design and are used in engraving only tough materials such as steel

Micrograin Carbide - introduced about seven years ago, Micrograin carbide cutters have given the engraver the ability to engrave a number of materials and decreased the need to resharpen cutters as much. These cutters tend to be very abrasion resistant (they hold their edge longer) and their strength is almost that of HSS. Because of their flexibility most of the specialized cutters that you see in the preceding pages are made of Micrograin carbide.

Typically many engravers have relied on the conical, half – round rotating cutter with a 60 degree included angle. The only difference between each job was the tip size and possibly variations in the cutters speed.
As many publications have pointed out …” One cutter is simply not designed to handle the wide array of tasks an engraver is faced with”.
Today manufacturers have designed a number of specialty cutters for the engraving industry. With a little bit of practice these cutters can help make many of your jobs a lot easier.

Conical / Tapered Cutters

As discussed conical cutters are the most common cutters available. These cutters come in either half round or quarter round configurations. Most lettering and surface engraving are done with these cutters.
Although half round cutters have been the most popular conical cutter, quarter round cutters are becoming the choice of many engravers. Although quarter round cutters are not as strong as half round cutters they have been recommended more by manufacturers because they clear out the engraved chips quicker. When engraving in plastic this cuts down on the melting of the plastic, while in metals this cuts down on the breakage of cutter tips. In metal it is the chips that will ruin a cutter before the edge becomes dull.
To make cutters stronger and last longer a gold coloured titanium nitrate coating has been applied to these cutters. This makes the cutter last longer on both the initial cutter and on subsequent resharpings.

Parallel Cutters - these cutters are used to create an engraved groove with vertical side walls. These cutters are used mostly for profiling, slotting and hole cutting where a vertical side wall is desired. These cutters can be resharpened.

The previous two cutters are classified as single fluted cutters, that is they have one cutting edge now we are going to introduce a multi fluted cutter.

End Mills - although parallel cutters are very important many engravers have found that if at least a 0.090 cutter can be used they would prefer to use an end mill. Just like the parallel cutter, the end mill will give you a vertical edge on your profile or cut out design. However unlike the parallel cutter, the end mill will give you a smoother edge finish especially on acrylic and metal. Another positive point for end mills is that because they have more than one cutting edge (they have multiples in 2,4,6,8,etc..) They will cut faster than parallel cutters. One more important factor is that end mills are stronger than parallel cutters.
One downfall to end mills is that they cannot be economically resharpened. It is for this reason that we suggest titanium coated end mills as they will last a lot longer under normal conditions.

Ballnose Cutters - used mostly for engraving in acrylic, the ball nose cutter will give you a vertical side and a rounded bottom. This gives a very smooth and decorative 3 dimensional look. As with parallel and end mills ballnose cutters are available in a single fluted design or a two fluted design. Both have the same properties as parallel (single fluted ballnose) and endmill (two fluted ballnose) cutters.

Beveling Cutters - as with ballnose cutters, beveling cutters are available in a single fluted conical design or in three fluted design. Single fluted cutters are very common, however a three fluted beveling cutter will give you a smoother cut on your edge (it produces a 45 degree cut). This cutter also works well in spot drilling.
Also available is a cutter beveler. Thus, instead of cutting and beveling in two steps you can do it in one step with this cutter. This cutter can profile and bevel all at once i.e. Badges. Cutting nameplates out of sheet stock.

Burnishing Cutters - burnishing cutters are normally used to engrave lacquer- coated metals. Used in conjunction with a “featherweight”. This cutter floats on top of the material and strips away only the lacquer coat. The over all effect is excellent. Burnishers are used also when you need a thicker line than you can get with a scratch engraving tool. Just as with conical cutters, burnishers come in varying widths i.e. .025, .030,.090 etc.
Traditionally burnishers have been solid carbide, however there is a new burnisher on the market which incorporates a diamond to do the cutting. Initial results show that this tool is superior to the solid carbide burnisher in cut and life. It also cuts better into aluminum. It does a good job in anodized aluminum.

Deep Wood Cutter - this cutter was designed to engrave in wood . Not only does it give you a deep cut but it gives you a nice straight cut in on the edge of the wood.

Dovetail Cutter - these cutters were designed for the specific application of cutting a dovetailed slot i.e. a slot/channel that has angled side walls (just like the slotted channel on a pantograph copyslide). The most common use for this cutter is in creating sign directories. This cutter is used to cut a series of slots in a plastic blank. Once this is done you can side in a beveled piece of plastic into each of the “slots”

Fly Cutters - this cutter is used when you want to engrave a letter over 2 ” and you do not want to use a multi-line font (especially if you want to engrave fast or hate those “grooved” cuts in the letters).
A fly cutter contains a cutting tip that is larger than the shank diameter. The cutting tip is offset and thus a 1/8″ cutter can make cuts up to 1/4″.

Glass Cutters - the most common type of cutter used for this application is a diamond burnisher. A long with coolant a good look can be achieved.

Stencils Cutters - this cutter was design to cut stencils out of thin brass or plastic.

Pyramid Cutters - this cutter was designed to help the engraver engrave into some of the new and harder surfaces that are commonly found on higher quality pens and pencils

This short discussion shows that their are a number cutters available to help you the engraver achieve the best look to your job with accuracy and ease of operation. However, remember that the recommendations of these cutters come from discussions with manufacturers our own experience and the experience of other engravers. Thus what works for one person might not necessarily work for another.

I hope this article has been educational to you. For further reading there are a number of good articles in the Engravers Journal which deal with cutters and their applications.

© Copyright 2003 by Awardline.com

Important Facts about Diamond Tools

Engravers Express supplies diamond drag engraving tools in 6 standard angles in all shank diameters and lengths, also glass engravers, diamond burnishing tools and a large variety of custom diamond tools. These tools are manufactured in the US utilizing only natural diamonds permanently bonded to stainless steel shanks.

The Characteristics of Various Angles of Diamond Drag Engraving Tools.

1. The Sharp Angles (90 degree diamonds)

The 90 degree diamond graver has the sharpest angle of the available engraving tools and was designed to produce very fine lines, small and delicate engraving, “and is the tool of choice for coated pens”. It also provides additional reach around a small diameter curved piece such as a pen.

Some caution must be exercised when using the sharp angle tools. They should not be used for general-purpose engraving. The sharper angle allows the tool to cut deeper and pressure must be correspondingly adjusted. Deep cuts are not desirable as there is a tendency to build up a berm on the sides of the engraved lines. Damage to the work can also result.

2. The Standard Angles (120 degree diamonds)

These are the most popular of the angled diamonds and are designed for general purpose engraving. Most machines come with one of these angles. There is very little effective difference in the performance between the two.

3. The Wide Angle Tools (150 degree angles)

These engravers are for soft metal such as gold and pewter. They produce the widest lines and have the least tendency to dig into the soft material. Again there is little difference between the two angles. The 150 will cut a slightly wider line.

Polish is the Key to an Excellent Diamond Graver

Proper diamond engraving tools are first cut and shaped to a perfect cone, then polished and lapped to a mirror like finish. The mirror finish at the very tip of the diamond gives the high quality brilliant engraving work. It is easy to inspect diamond tools for polish with a jeweler’s loupe. There is a remarkable difference between a polished and non-polished stone. This will also become noticeable in your work. Rough tools have higher friction and tend to rip, and leave tracings of their roughness in the engraved lines.

A highly polished graver can only obtain the highest quality luster.

The Right Tool for The Job

In order to be able to select the right tool for the job every engraver should have one graver from each angle group (Sharp Angle, Standard Angle, and Wide Angle) end a backup for the tools that he uses most often. Worn Tools Can Damage Work and place excessive strain on your machine.

Diamonds last a long time. They are the hardest substance know to man and have abrasion resistance qualities that are superior to all other materials.

But Diamonds Do Not Last Forever!

Periodically inspect your diamond gravers and your work. If your work begins to loose brilliance when compared with work done with a sharp diamond, replacement will bring back the quality. When you change your diamond compare the last work done with the old, and the first with the new. The new diamond will cut a sharp “V”. The old will dig a furrow with a rounded bottom, more like a “U”. More pressure is required with a dull diamond and excess material will be pushed up on the sides of the groove. This excess pressure can damage your work, and your machine.

Change your old diamond to a fresh new diamond tool.

How to judge when a diamond tool needs to be replaced.

It is difficult to exactly estimate the life expectancy of a diamond graver because there are so many variables: amount of use, types of materials, experience of the operator etc. Further, the tools wear slowly and the decline in quality is so gradual that it is difficult to notice.

Changing Tools by the Calendar

The best approach is to evaluate the amount of work you do and the types of material that you engrave. Then establish a schedule by following these general rules of thumb. Note the dates on your calendar. Here are some suggestions:

Low Volume Shops – General Purpose Engraving – Change Annually

Note: Occasional engravers can stretch that if their work on close inspection remains good, but when you hear of tools lasting for several years quality is suffering.

Moderate Volume Shops Change Semi-annually to Quarterly – depending on the nature of work and previously mentioned variables. These dates should beset by your seasonal demands and actually marked on the calendar.

High Volume Shops – can change as often as weekly. Industrial engravers doing both high volume and hard materials like stainless or abrasive materials may be changing daily.

Survey of Engravers A survey by “Engravers Journal” estimated an average period of 8 weeks for busy engravers and trophy shops.

Remember your work can not be good if your tool is worn or is of poor quality.

The most elaborate and expensive engraving machine or the most talented engraver is only as good as the tool that is being used.

Diamond Burnishing

Burnishing will solve a number of your engraving problems and expand your business horizons. Diamond Burnishing can cut you’re engraving time in half and at the same time give you a superior product. Burnishing can do the job in one pass where two or more passes may have been necessary using diamond drag techniques.

The diamond burnishers are engraving tools that can be used in all manual and computer operated machines with rotating spindles. It is advisable to use an “EZ Rider” spring-loaded cutter knob to replace the standard brass knob. This attachment will allow the constant light touch that burnishing requires.

Diamond burnishing vastly improves the appearance of the many coated or anodized metals. Drag engraving will not produce the brilliant and polished effect on materials such as “Black Brass”, nor is it possible to produce wide lines with the drag engravers.

Diamond Burnishing Tools will _do it all. Standard diamond burnishing tools are available with tip sizes of: .003″, .005″, .010″, .015″, .020″, .025″, .030″, .040″, .050″, and .060″. Custom tools are also available to solve unique applications. A .015″ or a .020″ tool would be an excellent first choice.

Note: Your diamond burnishers also double as glass engraving tools!

Why Diamond for your Burnisher?

Diamond is the hardest substance and the most abrasive resistant. It lasts and lasts.

The unique geometry of the diamond tool will provide a very highly polished engraving line. The diamond edge is sharpened to micro precision tolerances and will last and last.

Attractive burnishing of aluminum is now possible! The diamond produces a polished, brilliant silver line.

ENGRAVERS EXPRESS’S NEW Rotating Pen Engraver

The new rotating pen engraver opens up new engraving possibilities. It brings the highest quality engraving to coated pens and will engrave many pens that were previously deemed unengravable. It is available for rotating spindles utilizing the 1/8″, 11/64″ and 1/4″ diameter shanks in all lengths. A featherweight cutter knob is recommended.

© Copyright 2003 by Awardline.com