Fixing threads

DGY

DGY

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Good day all, I have an old Marble’s “Game Getter” scope mount that belong on my Browning BAR, there is one screw hole in the ring base that is striped and I was wondering if there would be a way to fix it w/o enlarging the hole re-tapping and using a larger screw(it will look ugly)! What about using some GB weld aluminum inside the hole and then after coating the screw with some release agent(past wax) threading the screw in and let set…. Would that work? Is there a better way?
Thanks
 
What will keep the GB weld in the hole... it would easily strip out itself.

What is the thread size of the stripped hole?
 
guntech said:
What will keep the GB weld in the hole... it would easily strip out itself.

What is the thread size of the stripped hole?
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There is still some threads in the hole, but not enough for the screw to catch the first few treads so when scope in in that screw doesn’t catch the threads and there for can’t be torqued.
Screw diameter is 0.1345”, length of threads(shank) 0.2380”, pitch 40.
What do you think?
 
When a threaded hole becomes stripped usually the screw also is partially stripped.

Sounds like 6x40 screws ... There is a slightly over size 6 x 48 tap and screws available from Brownell's Inc. It is designed to fix stripped 6 x 48 threads and I think about 10 thou larger... that may work. Some smiths had that tap and screws here in Canada... I never did.
 
guntech said:
When a threaded hole becomes stripped usually the screw also is partially stripped.

Sounds like 6x40 screws ... There is a slightly over size 6 x 48 tap and screws available from Brownell's Inc. It is designed to fix stripped 6 x 48 threads and I think about 10 thou larger... that may work. Some smiths had that tap and screws here in Canada... I never did.
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Thank you. The screws all look really good… hmmm what to do!
 
Only thing I can find so far in Canada is in metric….
If you guys are able to find a link for a 6-40 kit please let me know!!
 
DGY said:
We’ll finally found a kit on Amazon.ca for $90 free shipping!
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At that price, get a new set of rings and bases, either online or from your LGS

If you have any threads left at all, you could rough up the damaged part of the hole and put in some Titanium or Steel Putty.

Both of those products harden up very well after 48 hours of cure time and will give you appx 70% of the strength of the original steel.

I would purchase a screw that is long enough to go all the way through, past the good threads at the bottom and after coating it with some release agent, I would tigten it to the torque, or close to it, using the original threads at the bottom to hold until the Putty is cured. This way you won't have to tap the hole later and you will have 100% contact on the threads.
 
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I already have a bunch of other rings for that rifle, but that marbles game getter have a great little see through tunnel and is super light weight! So I will go the helicoil route and see how it work!
 
DGY said:
Only thing I can find so far in Canada is in metric….
If you guys are able to find a link for a 6-40 kit please let me know!!
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About any machine tool supply place will sell you the tap and probably a ten-pack of inserts. If the hole is a through hole, it's dead easy. If it's a really short, blind hole, it's a PITA, and you need a second tap, that you will need to carefully grind off flat on the end, so as to be able to thread right to the bottom of the hole.

KBC Tools online lists inserts by the each, around two bucks or so. Taps are around twenty each. If they don't have it, they can get it through their supply channels, usually. The taps are marked with the letters "STI", which means they are a Screw Thread Insert tap.

Seen a couple pretty upset guys that found that out the hard way, because they just read the tap size, and blew a bunch of oversize holes in their parts.

You can make your own insertion tool. Find a drill shank or wire that is a nice fit in the helicoil, file away about 2/3 or a bit more of the diameter of that wire, on the end that will be used to drive the insert, Check for fit in the loop of the insert drive tang. Use the back end of a nicely fitting drill bit, or the same size wire you made the drive tool with, to break off the tang when done.

If you need a guide for the insert, drill a hole in a piece of material, and tap it with the helicoil tap, screw the insert in to that, and place it over the hole and guide it into place as you turn it.

The inserts are sized by the number of diameters of the hole that is being threaded, so when you see it says 1D, or 2D, that is one or two diameters of the hole that is threaded.
 
I have some inserts, coils ,had for years, not 100% sure in size, I think they are # 6 I could send you a few, but don't have the tap for them, maybe a standard ? size would work?, but next size up is wrong pitch.
A am not at home , so can't check of a day or so.
 
marshall said:
I have some inserts, coils ,had for years, not 100% sure in size, I think they are # 6 I could send you a few, but don't have the tap for them, maybe a standard ? size would work?, but next size up is wrong pitch.
A am not at home , so can't check of a day or so.
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Thanks marshal, I have a kit coming in soon.
 
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