Stripped 10/22 receiver - question about tapping.

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b7tac

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I stripped 3 of the mount holes in the top of my 10/22 receiver. One hole is stripped worse than the other two, but I think I stripped the other two to the point where they wont be secure for long. I am going to tap the holes to the next bigger size (from 6-48 to 8-40). I think it will actually be a little stronger with the bigger threads anyway.

Here's my question. Can I just tap the receiver over the existing threads, or is it necessary to drill first. I would think with how soft the aluminum is, it would be easy for the tap to rethread without drilling.

I wanted to see what you guys think before I do something else that I am going to regret.
 
6-48 = #31 drill = .120".
8-40 = #28 drill = .1405".

= .0205" difference = A Lot!

I would clamp the receiver in a squared up drill press or mill vice and clean up the holes with a#28 bit.

Then without moving the set-up, Chuck the 8-40 tap in the drill Chuck, and using lots of thread cutting lube.
Hand turn the Chuck, by hand.

Backing the tap out frequently to clean off the chips and re-lube each time.

Aluminum is 'sticky' and a new sharp tap + cutting fluid is necessary to prevent grabbing / galling and pulling out the new threads before you get done.

Above all?
DO NOT try to free-hand it on the kitchen table!

You only get one chance per hole, and you better do it right the first time, each time.

rc
 
I agree with RC, even if you think you are being overly cautious, do it his way. Like he said, you get one chance with this. I used to tap ALOT of aluminum for a living, it can turn on you so fast you won't believe it.
 
That's why I come here to ask. I was thinking the larger tap would cut the threads and eliminate the need to drill.
 
Nope!
I wouldn't try it.

It might work?
But what if it doesn't on even one hole?

See where this is going?
Back to what I said in post #2.

You only get one chance per hole to do it right the first time.

rc
 
That's actually the route I am looking into. The threads inside the existing holes aren't terrible, but the screws won't snug up the way that they need to. I think this may just work. If it doesn't, I will have to go to the 8-40. I don't care if the holes are a little odd sized, but once the mount goes on it's staying.
 
Which one of my posts made you feel it necessary to tell me what I'll feel like if I don't/won't listen?

Anyways, I tapped the hole with the slightly oversized 6-48 screws from brownells. Tapping over the existing threads was so easy a monkey could do it and the base now tightens down perfectly. Thanks for everyone who had constructive advice. I definitely recommend the oversized screws for anyone in this predicament.
 
FWIW I have tapped a lot of aluminum and the best lube is soft bees wax. Working on sailboat masts you can use a battery drill and just drive the tap in using a slow speed and a tap gunked up with bees wax. No kidding.:scrutiny: Using the drill press or a jig to get things squared up IS the way to go when mounting things such as a scope bracket though.
 
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