Metal Polishing: Do This, Not That

Professional gunsmiths have a love-hate relationship with Dremel tools. They hate the Dremel because it has wrecked more serviceable firearms than all other tools combined. They love the Dremel tool because, let’s face it, amateur gunsmiths with Dremels are a big part of what keeps professional gunsmiths in business. So you want to do some metal polishing yourself to smooth a trigger or clear up a cloudy spot on a stainless steel barrel, but you don’t want to ruin the thing and have to pay big bucks for someone else to fix your mistake. Put the Dremel down, and let’s talk.

We need to make a distinction between polishing for appearance and polishing for performance.  Polishing for appearance should be mostly limited to stainless steel parts, since taking ordinary steels down to bare metal leaves them very vulnerable to rust. The “finish” of stainless steel is nothing more than the fact that all the scratches are small and running in the same direction. The smaller the scratches and the more uniform their direction, the smoother and shinier stainless steel becomes. Polishing for performance means you are attempting to smooth a trigger or remove an imperfection from an important moving part to help increase reliability, and this carries a different and important set of requirements having to do with the hardness type of the metal.

Some metal firearm parts are “through hardened,” meaning that the metal is the same hardness throughout the part. You can file, sand, and polish these parts extensively, removing metal and changing the shape of the part without ill effect. Regardless of the shape of the part or how polished it is, the part will continue to be as tough as it was before you began removing metal. Other parts are either “case hardened” or treated with a coating that hardens the surface of the metal, like the famous “Tenifer” process used on Glocks. In these parts, the metal underneath the surface is soft and protected by a hardening method that only affects the surface. Shaving metal off the surface with a file or sandpaper, or overzealous polishing, cuts through the surface hardening, exposing the soft metal underneath. This is why plenty of amateur trigger jobs feel great for the first 100 rounds and then quickly go downhill from there. An initially great trigger feel accomplished by modifying surface hardened trigger parts will start to feel gritty, then develop false stages, and eventually fail to function entirely. With the surface hardening gone and the soft metal underneath exposed, the parts will batter each other to death in short order and require replacement. Find out what kind of metal your parts are made from before polishing. If they aren’t through hardened, you will only be able to do a minimal amount of polishing, taking care not to cut through the surface treatment, or you’ll render those parts into junk.

Now its time to actually polish. I see you reaching for the Dremel again—alright, alright. You’ll want to use the little cloth wheels, ignore all the other attachments. How fast the cloth wheels do their job depends on what kind of polishing media you use. A rough polishing media will “cut” faster than a fine polishing media. The fine polishing media will allow for a smoother finished product. You want to really load up the wheel with polishing compound because the compound does the work of polishing, not the wheel. A cloth wheel without compound will destroy itself against the metal without polishing anything at all. Hold the part steady by putting it in a bench vise or other fixture, but be careful! Scratching the part when clamping it in the vise is pretty counterproductive, so protect it with plastic vise lip inserts, thick shop rags, or some other method. As you touch the metal part with the whirring polishing wheel, go lightly while holding very firmly to the Dremel with both hands. Pressing down too hard will cause the tool to gain traction suddenly, practically pulling the whole thing out of your hands and potentially ruining the part. Take it slow, take it light, let the polishing media do the work for you.

If you are going to be doing a lot of polishing, I strongly suggest ditching the Dremel altogether in favor of a real buffing wheel, which replaces the tiny little cloth wheel with a 6” to 12” diameter wheel on a spinning fixture. Using the buffing wheel, you hold the part in your hands and press the area to be polished onto the stationary wheel, which spins at high rpm. Very small parts, like a 1911 disconnector, can be ripped out of your hands by the force of the wheel if you push down too hard, so again, grasp the part firmly and press lightly, letting the polishing media do the work. A buffing wheel works very fast, polishing most parts in seconds. Unless you want the skin on your fingers polished off as well, gloves are mandatory.

With some practice and quality equipment in good condition, you can do your own trigger jobs and refine the finish on everything from stainless steel slides to grandma’s family heirloom cutlery. And if you muck it up, don’t worry! There is a friendly gunsmith nearby who probably needs another project to work on.