Sheared screw removal (drill and back out)
As gun owners, we’ll encounter screws, pins and fasteners that are damaged in a number of ways. If we are lucky, removing them will be fairly straight forward, with the screw retaining some sort of shank, head or post to grab onto to facilitate removal. Sometimes we are less fortunate. In those instances removing the screw becomes much more difficult. In this post, let’s take a look at one way to remove a small screw that has sheared off inside a firearm.
Here is the screw we will be working on in this post. It is a mounting screw that has sheared off below the top of a receiver in a SAKO TRG 42. Removing it can be quite difficult.
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The first thing I always try to do is either back the screw out, or drive the screw through with a small screw driver. I apply pressure and hope the friction will allow the screw to move. While this rarely works, sometimes it does and when it does, it saves you a tremendous amount of time. In this case, it did not work. My next step is to try to drill the screw out.
I’ll try to drill a hole through the center of the screw shank, insert a tool and back the screw out. This means the hole you drill must be smaller in diameter than the minor diameter of the screws threads. Alternatively, some guys will drill out the entire shank and try to pick out the threads. I do this as a last step, if you are a few thousandths off of center you can end up removing the female threads from the receiver and damaging an expensive firearm.
Once I locate the center of the screw, I use a center drill to spot the center of it. Depending on how the screw sheared, the material you are looking at may or may not be directly over the screw shank. In cases like this I try to refer to a print and indicate off one end of the receiver to locate the position of the hole.
Next, I make a hole through the center of the screw. In this case I used a ball end mill to make the cut. While end mills aren’t the best tools for drilling holes, they are very rigid and do not deflect much, especially at slow feed rates.
Finally, I remove the action from the milling machine. I find a small Allen wrench that is oversized to the hole and tap it into the hole. This forms the screw shank around the tool. Now I simply unscrew the broken shank.
Most of the time this will work. On the off chance it doesn’t, I’ll often run a helical milling cycle on the milling machine to remove the rest of the shank and pull what is left of the threads out with a dental pick.
The important part of attempting to remove a sheared screw is to make sure that your method works without causing any damage to the firearm. If you don’t think you can pull it off, it might pay to hire a professional.