Removing Stuck Gun Screws
Proper Tools and Patience Are Key
Sometimes working on guns can be less than a joy. It has highs and lows. On the low end, few things cause as much anxiety and frustration as trying to remove an overly tight-fitting screw and stripping out the slot in the head — or even worse, breaking the head or shaft off completely and leaving the threaded portion stuck in the gun. UGHH!
The prospect of removing a broken-off screw is justifiable cause for grave worry. It’s a time-wasting mess that can easily be made much, much worse by your “corrective” efforts. Let me offer some guidance to help you make the right decisions to get you through the perilous ordeal of extracting stuck screws.
A little vibration goes a long way and using a brass punch
minimizes the chance of damaging steel parts. You also
don’t have to hit the punch like a steel-drivin’ man!
Don’t overtighten screws! They are always meant to come out
with a screwdriver and moderate effort. Rather than a wild amount
of torque, this front trigger guard screw uses a smaller locking screw.
When the edges of a screw slot are badly damaged and V-shaped,
a steel flat-nosed punch can be used to tighten up the slot. The
vibration will help loosen up the screw too. Protect the wood and
metal in case the punch slips.
Proper Technique
For starters, try not to break them in the first place. The screws on a gun aren’t designed to be physically challenging to remove. Hercules didn’t install the action bolts at Waffenfabrik Mauser a century ago. If you can’t get them out with a screwdriver alone, something is wrong.
To install or remove screws properly, a high-quality gunsmith screwdriver set is a must. Mine is a 90-piece set from Real Avid (between $80 and $120 online), and I’ve yet to find a screw slot that I couldn’t match a bit. To maximize the torque (turning force) applied to the screw slot, you need to match the bit as closely as possible to the slot’s thickness and length. Any slop between the slot and bit robs you of torque and invites “boogering-up” the slot and possibly the gun’s finish if the bit slips out.
If the screw slot is already damaged, I recommend tightening it up with some careful peening to restore the displaced metal to the original location. You can do this with a flat-point steel punch and a small hammer. The gun needs to be secured so it doesn’t move while you do this. A screw head with a good slot, well matched to the screwdriver bit turned under moderate pressure in line with the center axis of the screw should come right out.
Apply a few drops of penetrating oil to the screw head and hole,
from both sides if possible, and give it an hour to soak in.
Then do it a few more times. You can’t over-lubricate!
Heat expands the metal that also helps break apart the
rust and debris between the threads of the screw shank
and the hole. Here, Frank uses an improvised shield made
from aluminum flashing to focus heat on the screw.
Next Level Removal
If a screw won’t turn out with moderate force or the screwdriver tip begins to bend, something is seriously wrong. Usually, the problem is one or more of the following — it was overtightened by a careless brute, rust or other corrosion has anchored it in place, the threads were clogged with dirt when it was installed, there’s mechanical damage like a peened end or bent shaft, it’s been purposely retained by an arsenal-applied stake, punch or chemical thread locker (ex. Loctite). Less often, it’s cross-threaded in the hole.
Many times you won’t know exactly what the problem was until you get the screw out. Address the problems you can see and assume the ones you can’t are present too. Use patience, penetrating oil, vibration, judiciously applied heat and the correct screwdriver bit. Combined, these five things maximize your chances of successful screw removal without breakage.
Lubrication, vibration and heat will reduce the torque needed to loosen up screws locked in place with clogged threads and/or corrosion, and will likewise help ease the removal of damaged screws.
Some mechanical damage, like a mushroomed end, requires correction before you attempt removal. You’ll find this type of damage on screws with exposed ends, like the ones that hold on sling swivel loops or attach the rear of the trigger guard to the action’s tang. An oversized tip presents a serious removal problem because the extra torque needed to swage down the mushroomed end and spread open the hole is going to exceed the strength of the material itself. This usually results in the screw breaking. To avoid that, I carefully remove the mushroomed end with files or a tiny sanding drum or grinding stone in my rotary tool.
A heavy retaining punch mark or staking mark may need to be drilled out before the screw can turn. You drill it out or grind it away with a rotary tool on the screw itself, not the frame! Carefully mark your starting point for the drill bit with a sharp center punch. There’s no need to drill all the way through the screw head and weaken it. You just want to remove most of the displaced metal locking it in the hole.
The thickest diameter gun screws are usually no more than ¼”. This means they are all on the small side and very easy to break by over-torquing. They are rarely hardened. Always work a stuck or tight screw by hand, slowly, so you can feel when the screw starts to turn and when it starts to hang up. Once a tight screw starts to turn, it may get easier and easier to turn, which is a sign it is going to come out with no further trouble.
Alternatively, it may tighten up again. If you feel it tighten, don’t try to turn it any further in that direction. Instead, reverse the direction until it tightens. Repeat this process, going back and forth, to loosen up the screw in the threaded hole gradually. As you turn back and forth, the penetrating oil is drawn deeper to lubricate the threads until it eventually comes out.
A screwdriver bit should tightly fit the slot. Using quality
gunsmith screwdrivers means more of the torque is actually
being applied to turn the screw
For penetrating oil to get into the threads efficiently, you need
to remove surface rust and dirt. This OTIS Technology pick set is
handy for the job. Ultrasonic cleaning tanks can work wonders on
stuck screws. Pistol-sized and smaller tanks are available in the
$100 to $400 range.
Gunsmithing Considerations
If you are going to remove stuck screws without mishap, you just can’t have the gun free to move around on the work surface. A bench block is a second-rate substitute for holding the gun solidly in a vise with aluminum or copper-padded jaws. Be careful not to crush the gun or mar the finish. You want it tight enough that it won’t move under the downward pressure and turning force of the screwdriver bit. Also, when firmly held, vibration is more efficiently transferred to the stuck screw because less of it is being bled off as movement or bounce. Holding the gun in a padded vise is a safety necessity when using heat to loosen screws.
This 1917 vintage No. 1 Mk III SMLE receiver has a broken
rear trigger guard screw. First, Frank uses a wire brush to
clean the area and then penetrating oil is applied.
Penetrating Oil Tips
Penetrating oil works faster when it doesn’t have to penetrate through dirt and rust scale to reach the threads. I use dental picks and a fine wire brush to remove visible detritus and expose the joint I want the oil to penetrate. OTIS Technology makes a nice gunsmithing pick set with multiple screw-on tool tips.
The unsettling truth about penetrating oils is they don’t seem to help as much as you would expect. From independent testing I’ve looked at, the best you can hope for from a single application is a 10% reduction in torque to loosen the screw. Most don’t work that well. If you have a screw stuck in a through-hole, make sure to apply the oil to each side.
Capillary action is what draws the oil in. Give the oil time to work its way into the threads. Here’s where the patience part comes in. Ideally, you would apply a few drops of the oil, let it soak in for a few hours, and then apply another few drops and let that soak in a few hours, etc., etc. At most, a day of penetrating time with multiple applications should be sufficient. You can’t over-lubricate, though the reverse is possible and undesirable. Warming up the parts, as well as subjecting them to vibration, will help the oil penetrate into the threads by causing the screw and hole threads to move slightly.
The oil is followed with vibration in the form of some
taps on the exposed end of the screw with a brass
punch and hammer.
Vibration Effect
The value of vibration, usually in the form of carefully focused hammer blows, is that shock waves carry through the metal to break apart rust and debris in the threads. A gun is immensely more delicate than an exhaust manifold, so don’t start beating on it with a 1-lb. ball peen hammer. A hundred controlled light taps from a small hammer will do more than you might think.
Sometimes I mask the area surrounding the screw head with several layers of duct tape for protection.
You can go more high-tech with your vibes, but it will cost more money. Twenty years ago I was visiting the aircraft restoration facilities at the Smithsonian Institution’s Silver Hill facility and saw them using big ultrasonic tanks to clean up rusty, dirty aircraft machine guns. They not only made the guns vastly cleaner, but the ultrasonic vibrations loosened up all the screws, making them easy to remove.
Since the screw head was broken off, Frank started to drill the
screw out. However, since the hole goes through both sides of
the metal, the loosened screw came out of the bottom with the
right-hand torque from the drill bit.
Finally, the ruined screw is out!
Bring Up The Heat
The last but equally important tool in your bag of tricks is heat. When metal is heated, it expands slightly. Heating a nut would cause it to expand slightly, enlarging the threaded hole and loosening its grip on the screw. When it cools, it shrinks back to its normal size. The nut will be easier to remove when it is hot than after it cools.
Fortunately, it isn’t always important to isolate the heat when trying to loosen a stuck screw. The expansion and contraction cycle will help to break up any rust and detritus jamming up the threads, making it easier for penetrating oil to get in and do its job. If somebody used a thread locker on the screw, heat will help break the bond.
If, God forbid, someone used red Loctite on the screw, you’ll have to heat the parts to 500 degrees to break the bond but temperatures over 400 degrees are best avoided because steels can lose their temper at temperatures between 400 and 600 degrees. You don’t ever want to put so much heat in the metal that you change its color, a sure indication you’ve altered the heat treatment.
Don’t even think of heating anything cherry red with an oxyacetylene torch. It will loosen the stuck screw all right — if you don’t melt it into the hole. It will also totally destroy the metal finish and whatever heat treatment it had.
My go-to heat source is an electric shop heat gun. It’s safer than an open flame and doesn’t leave the residue of oxidation on the metal. While your wife’s blow dryer probably won’t blow hotter than 200 degrees, a shop heat gun can exceed 1,000 degrees and needs to be used carefully.
