Save an Irreplaceable Screw





Introduction: Save an Irreplaceable Screw

 A friend has a nearly antique Stevens Nitro Special shotgun.  The screw that holds the forearm stock to the barrel had been bent and it would not seat fully.  (See the blue arrow for the location of the screw.)  He had been to a gunsmith who told him it was not any standard size and would be almost impossible to replace. 

(This photo is from

Step 1: The Screw and Its Receiver

 If I had known this project would turn out so well, I would have taken photos as I went.  The drawing shows a block of steel about 1/2 inch by 1/2 inch square with a tapped hole to receive the forearm screw.  My best guess is that the screw was turned partially into this block attached under the barrel of the gun when the gun or the barrel was dropped and the screw absorbed the impact.  Anyway, the screw would turn into its receiver only about three turns before it would go no farther.  The result was that the forearm stock was loose on the barrel.  

Step 2: A Demonstration

 Since I did not photograph what I did as I did it, I recreated the process with a common 6 x 32 screw and will demonstrate it here.  The three nuts on the screw show that it is straight and the threads work properly.  I included my watch to affirm I did not simply take before and after photos of this screw only seconds apart.  The original screw from the shotgun appeared to be just a little larger than a #8 screw.

Step 3: I Bent the Demonstration Screw

Here you can see the 6 x 32 screw after I purposely bent it about the same amount as the screw from the shotgun.  The nut is turned as far onto the screw as it will go now.   

Step 4: Tap With a Hammer

 I used a vise for this demonstration.  The steel receiver block mounted under the barrel made a vise unnecessary.  

As you turn the bent screw into the nut, the head of the screw will swing in an arc off of center.  Take notice of which direction the screw is bent by which way the head deviates from the center.  Tap against the direction of the bend a couple of times with a hammer.  Tap hard enough to return the screw head toward the center just a little.  Hitting it too hard could break the screw, depending on the quality of its steel.

Step 5: Turn With a Screwdriver

 After tapping, see how far you can turn the screw without forcing it.  You might gain a quarter of a turn, or you might gain more.  Then repeat the tapping from the last step.  Turn again with a screwdriver.  Continue this as long as necessary.

Step 6: Success!

 Eight minutes after beginning, the screw is straight enough to turn a nut on the full length of the threads again using only my fingertips.  The damage to the screw from my friend's shotgun was more complex and required more cycles of tapping and turning before it could go in far enough to pull the forearm stock firmly against the underside of the barrel.  

Step 7: Forearm Screw in Place

 This is the forearm screw as it should be.  Although the photo is not of my friend's gun, the screw seated as well on his gun as on the gun in the photo.  Previously it had protruded below the forearm stock surface more than the full thickness of the screw's head.  When I was finished, the screw was not quite in factory new condition, but the threads were much more crisp like they had been originally.  

Tapping the screw head and turning it down for more tapping is a good method when a replacement screw just is not possible.

(The photo is from 



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    Nicely done. It's the kind of wisdom an old engineer gives an apprentice. It's far too easy to lose these skills. That's what makes me see Instructables as a noble adventure.

    Thank you. I know others have thought of this, too. When my friend brought his gun to me I had to think for a while before I thought of doing what I did. If you like this, you might like this and this, too. Both involve doing things that normally require very refined and precise tools, but doing those things with rather ordinary tools and some careful thinking. I wish you much success as you try to help young people innovate.

    That gun looks like it needs to be cleaned.

    Could be. The image is from an on-line gun merchant. It is not the same exact gun my friend was getting ready for sale.

    since the shotgun is pretty old the screw is probaly a imperial thread such as bsp,unf,or bsf have you checked all the possible thread sizes?
    anyway great ible

    When my friend said his gunsmith was of no help in identifying the screwthreads, nor in offering a replacement screw, I took his word for it and went from there.  The gun is of US manufacture.  Metric threads were not being used in the US when this gun was made.  I would be surprised if an imperial thread was used, either.  I would think maybe the maker used his own thread to keep owners from tinkering with or modifying the gun.  I just do not know.  I am only glad we were able to restore the screw so easily.  I wish I had taken a before and after photo of the actual screw from the gun.  The difference was quite striking.  Thank you for your comment.

    Probably right about the custom thread, although it could also be to do with the thread profile. I vaguely recall that one of the issues that NATO has had in exchanging technology between US and European militaries is that there are different rounding profiles on the thread peaks and valleys - even when the thread is of the same pitch, it might not screw in cleanly, or might wear more than is safe.

    Interesting.  Thank you.

    thanks for the info you could also contact the manufacter of the gun or drill the thread of the female thread and retap it to another easier to find size

    I wonder whether this treatment might weaken the screw because of work hardening the steel? Obviously the bends applied are slight so it might not be an issue, but it's something to be conscious of, especially if the same treatment is required more than once.

    Not sure what to suggest to ameliorate it, either - annealing and quenching, perhaps?