January 29, 2012

Super Abrasives for Gunsmiths

Diamond-abrasive hand files and hones easily cut hard materials when other metalworking implements can’t do the job.

Gunsmiths have always had to work on case-hardened parts of firearm actions, such as hammers and sears, but now the trade must contend with semi-auto handgun slides and receivers being made harder as well. These harder metals mean we must use carbide end mills and drills for machining projects, and ‘smiths need a good solution for final-fitting problems. Because of the hardness of the metal on guns like Glocks and Berettas, aluminum-oxide, India or Arkansas stones will not cut very quickly. Getting a fine, positive cut on hard steels demands the use of diamond abrasives.

Diamond tools used in many manufacturing applications are available from tool supply houses across the country, but these items are often very expensive and do not last long. In our gunsmith shop, we have been using a single kind of diamond hones and needle files since 1978—the Eze-Lap brand—that have some great features. They are high-quality, American-made items, and are less expensive than other brands. Even better, they are made using a patterned heat-treating process for durability.

Likewise, diamond wheels save the gunsmith loads of time when more metal removal is necessary. Some of the best products of this type—the CSR brand—appear in a catalog from Armatt G. S., Inc. The CSR wheels work well, in our estimation, because they outlast aluminum-oxide abrasive wheels. Also, you don’t have to worry about keeping them dressed, and you can run them at a slower speed.

Tools & Techniques, Chapter 11

Courtesy, American Gunsmith

Use these three Eze-Lap Model L’s to modify hardened-action parts and to touch up your lathe and milling cutting tools. All of the diamond hones—in contrast to softer files and stones—work easy and fast on hard steel, high-speed steel and carbide bits.

Here are a few specific models in the Eze-Lap and CSR lines that we’ve had good experiences with:

The Model L Diamond Hone

This handy abrasive tool is an inexpensive diamond hone that fulfills most of our needs. It is a 2-inch by 11/16-inch diamond surface on a plastic paddle that comes in coarse, medium, fine and superfine grits. We have used all but the coarse grit in our gunsmithing. The fine-grit Model L Diamond Hone costs around $5.

We have used the fine and superfine Model Ls to correct sear problems in some models. They cut the hardest steels with ease. If you press downward, they remove the steel faster, but most of the time, only a light, controlled pressure is needed. We have used them to break sharp edges, polish flat surfaces and even touch-up our carbide and high-speed steel lathe and milling cutting tools.

Model 111f

Tools & Techniques, Chapter 11

Courtesy, American Gunsmith

Three diamond wheels (at left) and diamond needle files work well on small parts.

Lapping a metal surface flat means, naturally, that the gunsmith must use a flat lapping surface. For jobs that require this type of work, we use a Model 111f Eze-Lap hone, which measures 3 inches by 6 inches on its surface, and has four feet to raise it off a work bench. The larger versions are manufactured flat to .001-inch specifications.

A few, quick figure-S strokes on this hone are enough to flatten any part surface, and the 3 inch by 6 inch size conveniently handles finish work on sears, extractors and flat firing pins we have to make.

Model 62f

If you are doing custom .45s, you might want this larger Eze-Lap model to lap the bottom of slide rails flat.

Also, the 62f, which is a 2-inch by 6-inch surface mounted on a walnut base, finds use by many wood carvers to keep their tools sharp. Likewise, it works well on the few chisels we use in stock work, and Colt’s Custom Shop uses this model to sharpen engraving tools.

Diamond Needle Files

These instruments reach into small areas, and can solve many detail-work problems you might encounter.

Eze-Lap makes 12 shapes of diamond-needle files. The files come in sets of six each in both fine and coarse grits. We have found the 6oof (fine) set to have the shapes we need most, including a round, square, and three-square shape. The three square is what we used to straighten out the rear-sight dovetail on a Glock to install a Metropolitan rear sight. Also, we have used these files to recut the sear on a worn Timney trigger without disassembly by reaching into the mechanism and dressing the sear with one of these files. This worked well and saved us and our customer the time it would take for disassembly.

Tools & Techniques, Chapter 11

Courtesy, American Gunsmith

Large diamond pads can be used to sharpen carving and engraving tools and to flatten gun-metal surfaces.

CSR Diamond Wheels

The Armatt G. S., Inc., catalog includes a selection of CSR diamond wheels. This is a set of three wheels with three different diameters (5/32 inch, 3/16 inch, and 7/32 inch).

They come in a fine grit and can be used in your Dremel tool, since all have a 1/8-inch shank. We carefully use them to remove hard steel before the hand-finishing phase of a project.

Some of these wheels you can get from your local supplier; they are often carried as knife sharpeners.

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