SHERLINE Carbide Inserted Tip Cutting Tools

P/N 7600 (Holder)

I would first like to emphasize that I believe the prime method of cutting metals on a miniature metal cutting lathe should be high-speed steel. It's inexpensive, easy to sharpen, and can be shaped to make "form" tools. Insert tooling is expensive, can't be resharpened or shaped, but it can be a "lifesaver".

The obvious difference between carbide tools and inserted carbide tools is the tip is held on with a screw rather than brazed on to a piece of steel. This fact has a lot to do with the success of insert tools in recent years. Steel and carbide have slightly different expansion rates, which can cause premature failure of the carbide tip. It is surprising that a small screw will hold these inserts tight enough to accurately cut metal, but they do. We run 20-horsepower computer lathes at Sherline that can remove metal at a rate of 2 pounds (1 kilogram) a minute with these tools and have few failures.

The reasons I believe insert tools should have a place in your shop is they are ready to use, they hold their cutting edge when cutting exotic metals or abrasive materials, and can speed up the cutting process.

Normal cutting speed rules don't have to be considered to the same extent as when using high-speed steel. Stainless steel can be cut at triple the rate over high-speed steel with these tools. This puts you in a better horsepower range on the Sherline motor. Another interesting fact is you can get a better finish on some steels, such as cold rolled, by turning up the RPM. Insert tools don't need cutting oils to work well, but I still use a few drops now and then. This can be an important fact when working on your kitchen table.

I experimented with various tools before making a choice. I wanted a cutting tool that had a positive rake. I don't believe the tools we manufacture are rigid enough for negative rake tools which cost less and are far more popular.* These tools are designed for machines that weigh hundreds of times more than a Sherline lathe. Positive rake tools have to be sharpened at the time of manufacture, which adds to their cost, but also adds to their performance on a Sherline tool. You can't use any insert in these holders unless it has a positive cutting edge.

Another choice I made was the .015" (.4 mm) radius on the tip. A large tool radius can give good finishes on a full size machine, but it can cause havoc on small diameter parts or miniature machines. Large radius tools create high tool loads because of their large cutting surface. A radius smaller than .015" will chip too easily.

The difference between the 80° and 55° tools is that the 80° tool is a little stronger at the tip, but the 55° tool can get into corners. If you plan to only purchase one, buy the 55°. The 80° tool is a good choice to rough cut with.

To get maximum life out of these tools, be sure to increase the "feed" as you increase the RPM. The chip should have a tight curl to it and break off into short lengths. These chips can be very HOT. Remember, your hands are closer to the cutting edge when using miniature machine tools, so use caution.

Another plus for insert tools is their ability to cut hard or abrasive materials. Don't plan on machining down the shanks on end mills with them, but you can cut through a work hardened surface on stainless steel with ease.

These tools can simplify many machining operations, but will never solve problems caused by poor machining practices. As with all machining operations, WEAR EYE PROTECTION.

*NOTE: A negative rake tool holder designed especially for Sherline tools, P/N 7610, is now available. It is extremely rigid and allows the use of a 55° negative rake carbide tip which, because of the design of the holder, cuts like a positive rake cutter. The tool offers a cost advantage as well.

Sherline has teamed up with Valenite to bring the home shop machinist into the space age with cutting tools that add new dimension to small lathes. Until now, high-speed steel or brazed carbide tools were the only choices available to the owner of miniature metal lathes. High-speed steel had short tool life while brazed carbide chipped easily. Inserted carbide cutting tools have replaced these tools in the modern machine shop. Now your miniature machine shop can benefit from these same features.

The proper carbide insert has the ability to consistently give good finishes and long tool life at a much higher cutting speed. This is especially important with small lathes because they don't have excessive power at low RPM. With inserted carbide tools, you can cut stainless steel at the same RPM you were formerly using to cut aluminum with high-speed steel tools without any sacrifice of quality in surface finish.

Cost must be considered when selecting cutting tools, because these carbide tools are not inexpensive. However, they are worth every penny if you have problems grinding your own high-speed steel tools or cutting exotic materials such as stainless steel.

If you would like a good, solid, easy-to-use holder for these carbide tips, we suggest you start with the number 7615 right-hand holder that uses the number 7605 insert tip. This 55° insert is good for turning, facing and profiling. The 55° inserts have the advantage of being able to cut a larger number of different shapes. The 80° inserts are slightly less versatile but offer the advantage of longer tool life due to the stronger, squarer shape.

Boring bars come in a standard 6-inch length and are intended to be cut to length for each specific use. The 80° boring bar is intended for boring straight holes, while the 55° tool can do certain types of inside diameter profiling. Remember there is a minimum hole diameter for I.D. boring bars. (See tables on reversed side of this sheet.)

Sherline does not recommend attempting to cut hardened steels or piano wire with these inserts. Materials such as these should be ground to shape, not cut. However, abrasive materials such as glass reinforced plastics can be easily cut with these tools.

The main purpose of Sherline's diamond tip (P/N 7609) and holder (P/N 7619) is to true up commutators used in electric motors. The most unique aspect of this tool is that the diamond has four cutting edges. Although the initial cost may seem high, when you consider you are really getting four cutting surfaces rather than one, the cost in relation to the usefulness of the tool is quite reasonable. Diamonds, while expensive, are capable of giving mirror-like finishes to copper or aluminum. Never attempt to cut steel with the diamond cutter.

Your present Sherline tool post may be modified to accept these special tool holders, but an easier solution is Sherline's special tool post (P/N 7600) shown below. It is specially designed to hold all the tools shown on this sheet.

PLEASE NOTE: The inserted carbide and diamond cutting tools offered by Sherline will improve the performance of the Sherline lathe, but they will not correct poor machining technique. Rigid set-ups are a must for tools such as these.

NOTE: Items shown in the tables below are not sold in sets. The price in the "cost" column is for the insert holder only. Tool post and insert part numbers are provided for your convenience so you can see what is needed for a complete set. The P/N 7600 tool post is $15.00 and the insert prices are listed at the bottom of each section.

55° INSERT HOLDERS

Right hand shown (Left Hand opposite)
Insert: 7605, Tool Holder: 7615*

*NOTE: Sherline now manufactures its own version of this holder as P/N 2256 (RH) and P/N 2257 (LH) They are also available as a set as P/N 2258 at a substantial cost savings. Each Sherline tool holder comes with an insert, hold-down screw and Torx tool.

Insert: 7605--Tool Holder: 7635

Minimum Hole Diameter: .650"

80° INSERT HOLDERS

Right hand shown (Left Hand opposite)
Insert: 7608, Tool Holder: 7618

Insert: 7608--Tool Holder: 7638

*Minimum Hole Diameter: .550"

Outside Threading and Grooving Insert Holders

Inserts: 7606, 7660--Tool Holder: 7616

Diamond Cutter

Insert: 7609--Tool Holder: 7619

*Sherline's cost plus 20%

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