Question about drilling broken bolts

[BigRed_Ryno]

I'm with D.C on this too, decent sharp center punch, then start with a nice small pilot drill. did it on my mates CR250 cylinder just last week, slowly uping the drill size till literally just the thread of the bolt was left, and that came out with a screwdriver! didn't even have to re-tap it B) just take your time with it

[brapp]

i have always used an end mill if you can get the part clamped to drillpress or millign machine, or drill your pilot hole i prefer 1/8 inch cause 1 /16th basters anways break on me, but drillyour pilot hole then get a reverse twist drillbit and i have actualy used reverse taps as an easy out if the drill doesnt work. or drillit out wayyyyyyyy bigger and weld a nut into the hole so you ahve a nice threaded place to bolt to. btu it shoudl be a good weld and make shur eu have enough area aroudn the nut to hold the bolt.

[Dirtcrasher]

^ Oh, ABSOLUTELY. If I can get the part in the mill, there isn't a bolt in this world I can't get out. Big, small, short or tall a mill does it ALL!!!!!!!!!!

You can get things so close that you can literally wind out the dead threads like a helicoil.

As far as transfer punches go, they work great. But, in a case like this where that piece is punched out and basically a nut is welded underneath, whose to say that the threads are dead centered within that almost rectangular mount??

I guess I take my eyes for granted. I'm basically able to find centers by eye, especially if you grind it flat with a cut off wheel or similar to what Jeff suggested. I have really really good eyes, if I wasn't so stupid I'd do AOK

And IDK if I mentioned it, but you really want to drill that thing out as big as you can. THEN heat it up because that that point you have a very thin wall that heats easier.....

[Frankencelery]

I finally got it cleaned out...some of the hardware you guys were talking about is beyond me, but I needed some good cobalt drill bits, so I bought a left handed set, and drilled it out a little at a time. On one, it was just like Dirtcrasher said, the threads just wound out like a helicoil. on the second i had to get in there and sort of scrape out the bits. i then re-tapped it, but I hadn't planned ahead properly, and the drill bit size was too big for the tap I used, and the threads are rather shallow. I'm not sure if I should just run with it, or try to go bigger.

I did find the original problem though. These bolts didn't rust in place...someone used American bolt sizes in the holes. This is a major pet peeve. If you put a bolt in the hole, and have to lean on it to get it go in, either you're cross-threaded, or YOU'VE GOT THE WRONG SIZE! AAAAAAAAAAAHHHHHHHHHH!

Ok, I'm better now. I just can't get over people doing that.