Countless firearms, old and new, bear the marks, burrs and gouges that are the result of using the wrong tools for taking them apart. Here are several common gunsmithing mistakes to avoid.
In the interest of preventing this sort of thing, Kevin Muramatsu shares a few gunsmithing basics, from the most recent edition of the Gun Digest Book of Rimfire Rifles Assembly/Disassembly.
Screwdrivers: Always be sure the blade of the screwdriver exactly fits the slot in the screw head, both in thickness and in width. If you don’t have one that fits, grind or file the top until it does. You may ruin a few screwdrivers, but better them than the screws on a fine rifle.
A note on coin-slotted screws: Many action takedown screws and main stock retaining screws have slots designed for use with a coin, the theory being rthat a shooter in the field might not have a large screwdriver at hand, but would be likely to have pocket change. The slots in these screws are wider than normal, and the floor of the slots will be curved, to match the curve of a coin edge. It is possible, and advisable, for the gunsmith or advanced amateur to alter a large shop screwdriver to exactly fit these screws. In general, though, the following advice applies: Do not use an ordinary, unaltered large screwdriver on coin-slotted screws.
Slave pins: There are several references in this book to slave pins, and some non-gunsmith readers may not be familiar with the term. A slave pin is simply a short length of rod stock (in some cases, a section of a nail will do) which is used to keep two parts, or a part and a spring, together during reassembly. The slave pin must be very slightly smaller in diameter than the hole in the part, so it will push out easily as the original pin is driven in to retain the part. When making the slave pin, its length should be slightly less than the width of the part in which it is being used, and the ends of the pin should be rounded or beveled.
Sights: Nearly all dovetail-mounted sights are drifted out toward the right, using a nylon, aluminum, or brass drift punch.
One last tip: In gunsmithing, brute force is the enemy. If it doesn't come out with a light tap, there is probably a good reason – like a set screw, or you are trying to tap it out the wrong way. “Getting a bigger hammer” is generally not the solution in a gunsmithing situation.
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On screws, the author didn’t mention to never force one. If a normal torque will not bring the screw out, you will need to use heat (not on the screw, but the frame, and keep the screw cool), or a good penetrating oil to break the screw threads free, or both. A stuck screw will cause broken screwdriver bits, and a broken bit skating across the gun can do major damage to the finish.
On stuck screws, after using the above methods, we use a screw-jack, or jig, to hold the bit in one place on the gun, and over the screw, so that if a bit does break, the driver, and broken bit, can’t skate over the gun, as it stays in place over the screw.
On very expensive guns, where some screws are no longer available, and hard to make a replacement for, we grind a fishtail-like taper into the hollow-grind of the bit, where the tip of the bit is slightly thicker than the hollow-ground body above it. This allows the torque to be placed in the bottom of the screw slot, and not against the edges of the top of the slot, that will show on the finish.
On thin slotted, European-type, gun screws, watch the torque, as the thin bits are weak, and can break easily.
Finally, never use standard tapered blade screwdrivers on any gun screw, if you don’t want to mar the screw slot (I don’t use these screwdrivers on anything). Only use hollow ground drivers, or bits, that have a tight fitting, flat blade to insert into the slot. Look for cabinet-type screwdrivers, or bit sets, as they are hollow ground. I have been trying out the Weaver bit sets, and have found them to work as well as some of the more expensive brands. The largest set also has a coin-type, rounded-tip bit, that will fit most coin-slotted screws on take-down 22 rifles.
Great stuff Dixie – Thanks for taking the time to post!