Nothing can be more frustrating than trying to find the right screw to replace a missing screw or screw sets for mounting red dot sights or scopes. It’s true that many of the items you might want to mount come with their own screws, but not all. And even some of the screws that are included slip away into the tiniest and most obscure cracks of your workshop.
If you work on guns, it is inevitable you will need a screw here and there, and finding one that fits can be a daunting task. My local Ace Hardware has a section labeled Gun Screws. However, before it can be helpful, I need to know what size and type screw I’m looking for.
Screw Types
Some guns use screws that have American sizes and thread patterns. Naturally, European guns use metric sizes. A number of screw head types are also available, and having the right head type can be critical not just for cosmetic reasons, but often to make sure the part fits with the proper clearance. Finding the correct screw for any given position is a matter of knowing the length of the screw, the thread pattern, and the head type. The solution to the issue of not having the right size or type of screw or screwdriver comes to us in the form of kits.
Kits
We all know how messing up a screw head on a prize gun really detracts from its value and appearance. The key to turning screws without marring their appearance starts with having the perfect screwdriver tip for the screw. And, not just the right size, but a high-quality hollow-ground flat-tip screwdriver blade like gunsmiths use. Standard screwdrivers start tapering immediately from the blade tip. A hollow ground blade remains the same thickness or even smaller for a small distance before it starts to taper.
Wheeler Engineering has created a fantastic screwdriver set designed to meet the needs of all your gun projects and at a very reasonable price. This deluxe screwdriver set has just about every bit needed to work on any gun including specialty tools to help with disassembly and hollow ground flat bits specifically designed to match the thin slots in gun screws. It sure works well for me and gets called upon a lot more often than I expected when I bought it.
The kit comes in a plastic hinged storage box with two screwdriver handles and slots for each of the bits. In addition to any flat bit size imaginable, the kit includes popular sizes of Allen bits, Phillips bits, Torx bits, 3 punch sizes and specialty bits for Weaver/Ruger scope ring clamps, Redfield and Leupold windage screws, Mauser stock cross bolt bit, Millett rear sight adjustment bit, a 1911 grip screw bushing driver, Ruger/Colt single-action base pin latch nut bit, an M1/M14/M1A rear sight bit and several more specialty bits. The kit is easy to store and easy to use whenever you’re tinkering with your guns.
One American assortment of screws comes to us from Pachmayr, the makers of gun grips most of us admire. Sometimes you acquire a gun with screwed up or even missing screws. Enter the Pachmayr Master Gunsmith screw kit. This kit contains 12 each of 23 different screws including Fillister head, Oval head, and Plug screws in several different lengths and threads. All are commonly used for firearms and scopes.
The screws are stored in a 24-compartment plastic case. I have found this kit useful when I dropped a screw into one of those never-see-it-again corners of the shop or when I’ve encountered a rusted or damaged screw on one of my firearms. I’ve even helped some of my buddies replace damaged screws on older guns.
When it comes to mounting red dot sights or telescopes on modern guns almost all the holes drilled for these are metric, either M2, M3 or M4 sizes. I’ve found kits for these from two companies: iexcell and SYWISHKEY. They both have assortments that will cover most any project related to optics or other gun-related projects.
Lessons Learned
I can pass along a few lessons learned the hard way related to using the aforementioned products. One has to do with Allen heads versus Torx heads. The Torx screwdriver bits, also known as star bits, will usually turn an Allen screw, but in doing so will strip the edges of the Allen socket so your regular Allen wrench won’t turn the screw.
When sizing a screwdriver to a slotted or common screw, it’s important to match both the thickness and the width of the blade to the screw head. Keep the screwdriver bits in their original slot. That way you can just move up or down the row one or two bits to find the exact match for your screw instead of having to jump around in the case to try to locate one that fits your screw.
Allen and Torx bits have numbers to represent their size. However, slotted screws aren’t numbered so any number associated with a slotted screwdriver bit is relative to the bit, but you won’t find that number on a screw head.
You may want to keep a magnet with a telescoping or long handle nearby. The little screws tend to jump off the screwdriver bits or out of your hand and seek the tiniest, most out of the way places to lodge.
Threads can be tricky. In the Unified Thread Standard (UTS) system, manufacturers list the diameter size as a number between 0 and 10, with 0 being the smallest and 10 being the largest. Screws larger than a #10 have a diameter listed directly in inches. If you see a screw labeled 4-40, the first 4 is the size of the screw and the 40 is the number of threads per inch.
There is another label that might be on the screw package that would be either UNF or UNC. UNF threads are fine and UNC threads are coarse. Trying to thread a fine screw in a hole that was cut using a coarse bit does not work. If the screw identifying callout includes tolerance factor, it is telling you what kind of nuts or holes the screw is meant to fit into. A size 1 screw has the most space between its threads, so it fits more loosely when it is used.
If you damage threads or need to drill a hole, you can thread that hole using a tap and die set. If the threads aren’t too badly damaged, using a tap to repair them might work. Just make sure the tap size exactly matches the hole size that was there. Okay, I hope I’ve helped. Beyond what I’ve written here, experience is your best teacher. Just take things slow to avoid damaging parts on a good gun.
Are you a DIY gunsmith? What tips do you have for other DIY gun owners? Share them in the comment section.
The Deluxe Wheeler Kit contains specialty bits for Weaver/Ruger scope ring clamps, Redfield and Leupold windage screws, Mauser stock cross bolt bit, Millett rear sight adjustment bit, a 1911 grip screw bushing driver, Ruger/Colt single-action base pin latch nut bit, an M1/M14/M1A rear sight bit and several more specialty bits. One American assortment of screws comes to us from Pachmayr, the makers of gun grips most of us admire. A telescoping magnet comes in handy when retrieving lost screws or other small metallic parts. These are a few of the screw head types you will find when working on guns. This Wheeler deluxe screwdriver set has just about every bit needed to work on any gun including specialty tools to help with disassembly and hollow ground flat bits specifically designed to match the thin slots in gun screws. The solution to the issue of not having the right size or type of screw or screwdriver comes to us in the form of kits.
Great, helpful article. Thanks much.
An excellent companion to the Deluxe Wheeler Kit is the Wheeler F.A.T. Torque Screw Driver Kit. Great for getting scope mounts, rings, and other screws to the correct torque specifications. It’s available in analog and digital.
Thanks for a wonderful article on a subject most of us aren’t too concerned about until we are faced with a marred or missing screw. My most serious problem was in a new 2nd Gen Colt SAA that had a stripped threads in the frame where one grip screw had no hold. My temp solution was the old machinists trick of using a sliver of wood to tighten the screw. I’ve talked to a gunsmith about it and he recommends sending back to Colt for repair. Any other ideas?
I also use a Magnetic Parts Tray like those sold for auto mechanics. They can help keep screws from getting lost, and if placed Under the piece you are working on, can Capture falling screws so they Don’t get lost!….
Using the wrong screwdriver tip is the fastest way to diminish the value of your nice firearm. At best, you can mess up the head of the screw, at worst, slip and put a deep permanent scratch in your firearm.