Hollow- or parallel-ground screwdrivers are tools that no gun enthusiast should do without.
By Bryce M. Towsley
Almost all gun work will require screwdrivers, and it's extremely important that the proper screwdriver be used. Most screwdrivers sold in hardware, or home- or auto-supply stores have tapered ends. This allows them to fit a wide variety of screw slot sizes, and it also adds strength. But they are a horrible choice for working on guns and should never be used.
The reason is that a tapered screwdriver will cam against the taper as you apply pressure and cause the screwdriver to ride up out of the slot, which will cause it to go skidding off, gouging anything in its path. It might be your hand, which will likely heal, or it could leave an ugly gouge in the gun, which is forever. Either way, it's guaranteed to ruin the screw, probably making it difficult to remove without drilling, and certainly unsightly.
The pressure exerted by a screwdriver is amazing when it's applied to a very small surface. A tapered blade in a straight-sided slot contacts the screw only at the top of the slot. The forces applied to such a small contact area are enough to move the steel and cause the edges of the slot to round and strip.
A screwdriver must fit exactly in the slot of the screw, both in thickness and width. I cannot stress the importance of this enough. The sides of the blade should be either hollow-ground or with both sides parallel. A hollow-ground screwdriver will apply pressure to the bottom of the screw slot rather than at the top as a tapered screwdriver does. This actually helps to "lock" the screwdriver into the screw as opposed to trying to cam it out of the slot like a tapered screwdriver will. A parallel-side screwdriver will apply force for the entire depth of the screw slot, which distributes the force over a much larger surface area than a tapered screwdriver. A screwdriver that fits properly will fill the slot and have little slop and the maximum amount of contact surface inside the slot to distribute the forces being applied.
A properly fitting screwdriver will fill the width of the screw slot, which applies more leverage by moving the forces out to the very edges of the screw head. This is a simple principle of leverage. With all else equal, it's much easier to turn a large wheel than it is a small wheel. There is little point in having a large wheel to allow more leverage and then only turning it from the halfway point, which is closer to the axis and has less leverage. It turns easier when the force is applied to the outside radius, which is the farthest point from the axis. Think of the screw head as the wheel that turns the screw. If your screwdriver only fills half the "wheel," you lose leverage. But if it fills the entire slot, it's turning from the full diameter of the "wheel" and is utilizing all the leverage possible.
In days past, gunsmiths spent hours filing the blades on screwdrivers until they fit perfectly in the screws they needed to turn. Today, we have better options. Simply buy one or more of the many different gunsmith screwdriver sets available that are designed specifically for gun work. Some are fixed-blade, but the most economical are the sets that use detachable bits for a single handle. This also allows you to have bits for Torx, Phillips and Allen head screws. Here are a few that I have been using.
Brownells offers a huge variety of screwdrivers. In fixed-blade models, the best is likely the Fixed-Blade Gunsmith's Screwdrivers, which can be bought individually or in one of several sets. Brownells' Fixed-Blade Gunsmith's Screwdriver Super Master Set might be the crown jewel of gunsmithing screwdrivers. It's a bit pricey, but worth the money if you are serious about this.
Brownells also offers several interchangeable magnetic tip screwdriver kits over a wide price range. Mine is the top-of-the-line 58-bit Master Super Set. It includes two handles, one long and one short, 44 assorted hollow-ground tips, 10 Allen head tips, three Phillips head tips and a 1/8-inch square tip for some Remington buttplates. This is certainly one of the most complete kits available anywhere, and at a cost far less than it would be for this many individual screwdrivers. It has been on my work bench for many years now, and I don't recall a single problem or the need to replace any of the tips. That's a strong statement because these screwdrivers walk a fine line. If they are heat treated too much, they become brittle and will break, but too little heat treat and they will twist under pressure. At least on my set, Brownells got it exactly right. My only complaint is there are no Torx head tips included. But they can be added for just a few dollars more.
Midway USA sells the Wheeler Engineering Deluxe Screwdriver Set. This is a newer product, and I have been using one for a few months now. It seems to be a very complete screwdriver kit. There are 54 hollow-ground flat bits as well as a selection of Phillips, Allen and Torx bits. There are 17 specialty bits included in the "professional" set, which comes with two handles. The first is a regular-size handle that's good for most jobs, and the second is a slimmer, shorter "Close Quarters" handle good for finesse work with smaller bits. It's all in a plastic case.
You will also need a set of small "jeweler's" screwdrivers for some of the more delicate work you will encounter. Again, I turned to Brownells for its 12-IN-1 Precision Miniature Screwdriver set.
200 South Front Street
Montezuma, Iowa 50171
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5875 W. Van Horn Tavern Rd.
Columbia, MO 65203
Reprinted from the October 2005 issue of Buckmasters GunHunter Magazine. Subscribe today to have GunHunter delivered to your home.