Tapping threads - screwed

[nevada]

I bought a side scope mount for my MAK 90. It was made to use rivets but I thought I could just tap it and use screws. I bought the drill/tap and handle, the drill matched the holes already there so all I needed - I thought - was to thread the holes. Big laugh. I have just succed in drilling a larger hole by hand, with the tap, without a single thread in it. I used drilling oil, looked up a how to on the 'net, went by hand. I could have just put a match to $25. sucks.

[Jagman]

Make the hole in the scope mount the same size as the reciever holes and use a bigger rivet.
Jagman

[nevada]

I don't know anything about rivets, and don't want to go to a gunsmith. Bad luck with the two I've tried here. No holes in the receiver yet. There is a mount already tapped I can buy. I'm just ticked that I couldn't do something that's supposed to be easy. I couldn't get threads started in any of the three holes. Maybe the steel is too hard.

[tump]

what kind of screws are you using set screws or screws with a head? if your using screws with a head you don't need to tap the mount only the reciever .:icon_biggrin:

[Rampager]

Do they make heli-coils small enough for this?

If worse comes to worse you could always mig weld the scope mount through the holes and then grind them smooth. I did this on a hungarian AK build I did did last year.

[nevada]

The screws are round head ( mushroom or rivet shaped ) hex socket. The idea is to screw them from the inside of the receiver out into the threaded rail.

[Jagman]

As the bolts will be sticking out of the reciever to fasten the mount, if there is enough space maybe you could use a tad longer bolts and fasten it with slim nuts?
Jagman

[SSwee]

How thick is the plate you were trying to tap?
SS

[drhall762]

Just a note. Tapping though two pieces of metal that will be stationary with respect to each other can be a problem. The treads will not always line up once cut to allow a tight joint. The receiving piece, the piece that the bolts or cap screws are to hold in should be tapped. The piece being attached should have a clearance hole for the cap screw. Look at conventional mounts. The mount is drilled and countersunk for the cap screw. The receiver is the part that is drilled and tapped.

Don't know if this applys to your application or not.

Dave :sniper:

[vair65]

You might have used a tap with too course a thread and thats why you really don't see threads, try using the finest thread count tap, if you tap it again, and you might have better luck. It might be too thin to get any useful threads though. More thread's, more clamping power.

[nevada]

Thanks for the ideas, but I ordered the pre-tapped mount fron Tantals. The bolt was a #10, fine thread, so was the tap. The receiver is not going to be tapped, plain holes only. I don't weld, and the ruski scope is about two pounds, don't know if that would hold up. The area to be threaded would hold about 5 complete threads, a slim nut might work. Might have worked if I put the screw in from the outside of the receiver. Too late, I got mad and ordered the other one already. Drill three holes into the receiver, put the screws in and I'm done. If I ever want to tap some aluminum, I might try again. Thanks, fellas.

[Seattlefungus]

Check out the pneumatic rivet tool at Harbor Freight. Handles steel rivets... All for under $30.00