Drilling problem - AR15.COM

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Posted: 10/11/2004 8:38:15 PM EDT

I am trying to drill out the rivets on my AMD65 kit and I am having no luck.

I broke a high speed steel drill bit while drilling my pilot hole for the rest of the drilling on the reat trunion. I then upgraded to cobalt and broke a cobalt bit in the trunion while trying to extract that bit. Both are in pretty deep. All in all about 2/3 of the rivet is now undrillable.

Posted: 10/12/2004 7:45:16 AM EDT

[#1]

Hmmm..... did you use low speed and lots of oil? Is the trunion with the drill bits in your receiver or out where you can work on it?

Which hole is this (Top or Bottom)?
Did you try drilling from the opposite side with a fresh Cobalt bit?

Rear trunions are pretty cheap so at least you have the option of replacing it... I would try getting as much material removed from the opposite side and see if a good sized punch can get it back out.... You may also be able to heat it up and let it cool slowely to soften the metal of the bits but that won't help the Colbalt much!

Posted: 10/12/2004 7:54:15 AM EDT

[#2]

I'm with quarterbore, heat it. These rivets soften faster than the trunion, so if your broken bits are small, you can probably punch it out if its hot, depending I guess on how far you've drilled already. I'm not sure how heating would effect the strength of the trunion though.

Posted: 10/12/2004 8:04:37 AM EDT

[#3]

Quoted:
I'm with quarterbore, heat it. These rivets soften faster than the trunion, so if your broken bits are small, you can probably punch it out if its hot, depending I guess on how far you've drilled already. I'm not sure how heating would effect the strength of the trunion though.

Thanks, I think I will give it a try. I am just going to be building a pistol with this kit so I will be welding the trunion in such a fashion as to not be able to accept a stock anyhow, so strength is not a big problem.

Posted: 10/12/2004 8:17:59 AM EDT

[#4]

Quoted:

Thanks, I think I will give it a try. I am just going to be building a pistol with this kit so I will be welding the trunion in such a fashion as to not be able to accept a stock anyhow, so strength is not a big problem.

Then you are really good as the pistol trunions (if you can find one) are NOT that expensive if something doesn't go well! I have been using one of the MAPP/Oxygen torch kits and you can really get some heat where you need it with one of these but careful as these do get hot enough to burn steel!

Posted: 10/12/2004 10:42:25 AM EDT

[#5]

If you do use this trunion, strength is an issue to an extent. Every time the action comes backward during firing, it is the trunion that stops it. You definitely don't want a bolt carrier or spring in the face (or hip). I doubt the heating would hurt it, but I'd be careful just the same...

Posted: 10/12/2004 5:05:04 PM EDT

[#6]

I've been trying to find one, but Kvar says they don't know if they will be getting any more and nobody else has them that I have found. If you see any for sale, please let me know!

Quoted:
Then you are really good as the pistol trunions (if you can find one) are that expensive if something doesn't go well!

Posted: 10/13/2004 9:31:43 PM EDT

[#7]

So heating it didn't do a lot of good. I may heat it some more but at this point I am inclined to buy a new trunion unless anyone has any other ideas.

Drilling it out from the other end did not work. The bits are too far in.
It is the top hole.
I used the lowest setting on my drill press.
The bits I used were small which I think is why they broke. They were not seizing at all and they were not realy very warm before they broke.

Anyone found another supplier for pistol trunions? Please?

Posted: 10/14/2004 2:53:10 AM EDT

[#8]

Good luck!!

Posted: 10/14/2004 5:46:11 PM EDT

[#9]

Well, I can definitively say that heat is not going to get the bits out. I heated the thing today to try to get them out and ended up melting the biggest, hardest punch I had that would fit in the hole. I think I need a new trunion.

Quoted:
I'm with quarterbore, heat it. These rivets soften faster than the trunion, so if your broken bits are small, you can probably punch it out if its hot, depending I guess on how far you've drilled already. I'm not sure how heating would effect the strength of the trunion though.

Posted: 10/15/2004 10:41:04 AM EDT

[#10]

coffeeman,
I was just in a similar situation having a broken bit in the rear trunnion. Mine was then compounded by breaking the tip of a punch in there as well (don't ask).

Try using a small drill bit and remove as much rivet material from around the bit, and on the opposite side of where you where you lost the bit. When you have about 2/3's of the hole cleared up, then put the trunnion in a 4" drill press vise, use a very sturdy 5/32 flat tipped punch and beat the crap out of it.

Worked for me!

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