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 gunbroker.com.)

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.  

Comments

[ilpug]

That gun looks like it needs to be cleaned.

[Phil B]

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.

[sharlston]

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

[Phil B]

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.

[kissiltur]

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.

[Phil B]

Interesting.  Thank you.

[sharlston]

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

[kissiltur]

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?

[Phil B]

The application for this screw is rather light duty with very little torque on it.  Perhaps in some applications work hardening might be a problem.  My friend popped in on a Saturday afternoon and did not want to spend a lot of time getting the screw to work.  On balance, what I did worked out very well this time. 

I see you are in Portland.  We bought a house in Vancouver, WA for retirement.  I go to meetings in Portland near the airport about four times a year.  My wife's remaining family lives in Salem.

[kissiltur]

All very reasonable - didn't mean to imply otherwise! For some reason I thought the screw was taking more stress than that.

Yes, I've been in Portland since I moved to the States in 2001. It's home, and I like the fact that the landscape has more texture to it than Surrey near London, which was the last place I lived in Britain. We're a way from the airport now, though - used to live right nearby when my wife had a job there, but moved west to make commuting easier.

[RadBear]

Cool. I'm going to have to remeber this one!

[Phil B]

Thanks for your comment.  I am 63 years old.  During all of my avocational tinkering, this is the first time I have had to do what I described here.  I had considered several other strategies before I thought of this one.

[skunkbait]

Phil, Once again EXCELLENT instructable! 

As others have mentioned, one can almost always have a screw made, but the cost can make it impractical.  More importantly, in certain applications (antique/historical  firearms, tools, machines etc.) to have a non-original screw can greatly devalue the item.  This is an excellent solution!!!  I have at least two antique guns and a (pretty rare) 35-year old Bultaco motorcyle where this idea will come in very handy!

[Phil B]

Thanks, Barry.  As I have hinted, the threads on the forearm screw looked REALLY bad, but cleaned and looked almost factory new after the tap and turn treatment.  That was in addition to not being able to insert the screw more than about three turns. 

[l8nite]

 Thats a neat trick! To the nay sayers, yes its possible to find almost any screw or have a machinist make one if you have the time to hunt either down but if you can save yourself the aggravation with just a little time why not go for it !

[Phil B]

Thanks.  I hope it will be useful to you one day.

[Hands Without Shadows]

Finding a replacement screw is always possible. 

[Phil B]

My friend's gunsmith used his thread gauges and could not identify the screw.  He said he had never seen anything like it.  I took the gunsmith at his word (as reported to me by my friend).  My friend is out of work and is trying to get the gun ready to sell, so he was not interested in chasing down a replacement screw.  Perhaps you have sources or information the gunsmith does not have.  Thank you for your comment.

[fegundez1]

good idea I have used this type of method before but never on such an important piece. Being gentle and very patient is the key here. Good Instructable

[Phil B]

Thanks.  You are correct about going slow and being gentle.  I was pleased that the rounded, flattened edges of the threads appeared almost new when I was finished.  My friend wanted to force the screw through the threads.  I am glad we did not.

[microman171]

Depending on how keen to fix the screw you were...

Metal lathe + thread cutting equipment
A metal pin
A saw for cutting a slot

Not impossible...  Some people do this all the time.  They have all this gear in miniature for model making.

[Phil B]

Thanks for your comment.  A metal lathe for screw cutting would surely do the job.  I certainly do not know anyone with such a lathe.  I  also wanted to describe something anyone could do well with the most minimal very common equipment.

[masterochicken]

Cool.

[Phil B]

Thanks.