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Posted: 7/29/2005 4:30:02 AM EDT
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Any suggestions? I broke the small pilot bit in one of the front trunnion rivets on my AMD last night. It's below the surface. I have tried using another small bit to drill relief holes around it so I could pry it out but that hasn't worked. It was a cheap bit so I'm hoping that the good quality bit that I use to bore the hole to its final size will chew it up but I'm not sure that'll work. Thanks, Chris |
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Best bet is to take a small center punch and try to shatter what is left of the broken bit. Then tap it on a bench to remove the pieces. Trying to drill it out will at best just dull the new bit, at worst it may slide off and start another hole where you don't want it. Mike |
Good advice +1 |
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I don't think I have heard of a drill bit beaking but man do you need to slow down before you get to tapping or you are going to get screwed! You need to get good taps and learn to take your time and use LOTS of oil and clean the TAP every half turn or you will break a tap in there and getting a tap out is a much bigger PITA!!! This was a warning call... it's your kit but I have lived the fun of a broken tap and breaking a tap is easy compared to breaking a drill bit... and those taps are almost impossible to get out! |
Yea... drill bits break but just how small of a bit were you using... I have not built an AK in a couple months but you should be using Cobalt bits and if you were drilling out the rivets I assume you should be using a 5/32 bit... to break a 5/32 Cobalt bit in a front trunion is a sure sign you are doing something wrong... Now, if you were using something smaller, why would you be doing so? The 5/32 is the next size smaller then the #21 drill that is needed before you tap 10-32 so I sure wouldn't see a reason to be doing anything smaller... Anyways, the warning wasn't a critism of your drilling... it was really a warning that if you broke a drill bit you had better be prepared before yu start tapping as a broken TAP will really screw you up... You can ignore me if you like, but that will not help you if you break off a 10-32 tap in the bottom of a hole... Good Luck! EDIT: Here is some more info that I had compiled before... www.quarterbore.net/forums/showthread.php?t=163 Hope this helps some... |
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ITs easy to break small drills and taps especially no matter what anyone says. When you add things like uneven surfaces and drilling into pre existing holes your chances of breakage really increase. The method I use at work for busted drills and taps is compressed air first and a magnet or a pic. IF that doesnt work use a punch or something as hard as the drill to shatter it. In the machining world we have a saying, "if you never break or scrap anything your not learning". So dont feel bad 
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Same thing happened to me. I used a masonry bit - carbide tip - on a drill press on as fast a speed as possible. It drilled the broken bit out but took longer, with lots of heat and ruining the masonry bit as a result. The cobalt bits are expensive but worth the money. Use a slower speed and cutting oil next time and you will be less apt to break the bit. |
Thanks for the info. Over the course of dealing with this broken bit and trying to break apart the pieces of existing rivet I ended up elongating that hole. All the other holes turned out fine. Unfortunately I will have to bore this hole out larger and use a larger screw in this hole and it's match on the other side. I guess I'll be going to the local ACE Hardware tomorrow. Chris |
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