Got a toughie....broke off exh man bolts

One stud (3/8 NC)came out easy enough, another came half way out and snapped, the other 2 snapped right from the get go. All three snapped about 1 thread inside the head.

Got em drilled as close as close can be centered with an 1/8" pilot hole. Moved up to a 1/4" lefty. Fluted easy out (straight...not the spiral) just stripped through the hole. Got the holes out to about 9/64". No go with starting a tap, won't catch. Prick won't catch to peel the threads clean.

Heated and quenched to no avail ( first time heating was after center of stud drilled out). Tried going out futher with a drill but not enough meat for the bit to bite on. Just a small fraction on the shoulder of the bit, takes the edge right off. Reheated and let cool natural thinking the quenching put a hardness factor in. On reheating, can get about 1/8" cherry red out of about a short 1/2" of stud remaining in the head. The studs are not bottomed out in the blind hole and have drilled through. Went to the point of trying to blow the stud out on worst off center drilling. Too close contact, could tell was hitting the threads and quit.

Am at a loss at this point which direction to go from here.

Anyone got any ideas?????

Thanks Redmund for the hacksaw tip....it worked on one. One other was work hardened too much, blade didn't touch it. The last one was way in the back and of course all the wireing..plumbing..steering cables...just didn't have the room to manuvre a blade around.

Sitting there stumped again.. but making progress...had one out. Got to thinking I had a set of gunsmith drift punches in the drawer that hadn't been used since I closed the gun shop up 18 years ago. Ground one to point (very small center punch can we say???) and said to self if it's helicoil time, it's gonna be worth it. Second stud I just placed it at an angle with 2 good raps it slide under and I pushed it all the way through collapsing it enough a small screwdriver unthreaded it right out. The last one (back one) basically the same although it ended up collapsed in the bottom of the blind hole. Quick shot with the 1/4" lefty drill bit and it was gone too.

Never-siezed up the new ones and torqued the new studs into the holes. All "felt" good when I got to the bottom of the stud (studs are 1/4" short of bottoming the hole). Even the back one seemed to torque down. Those threads got a bit more dinged.

Thanks all for the advise and tips guys, and if anyone is in the SCMN area this summer (Fairfax) swing on by for a cold one.

Almost forgot...a FYI. The gunsmith punches I got from Brownells in Montezuma IA many many moons ago. Even though the equipment gets bigger and bigger....the tiny small stuff still saves the day. Won't be without those punches anymore, they got moved from the junk drawer to the toolbox now.

Bruce

Next time you run into a hard bolt, surface, etc: that needs drilled, use a copper clad carbon rod with a battery, 6v or 12v.

Peal back the copper about 3/4", sharpen carbon to a fine point, then with your thumb break off the pointed tip, hook the carbon to the negitive lead ( a welding electrode holder works well) and the base metal to the positive lead. Hold the carbon point on the center prick then attach the postive lead to the battery (jumper cables work well), heat metal to be removed until cherry red, remove postive lead, let cool slowly.

This will make a soft spot in the bolt so it can be drilled, cut, etc:. Depending on the bolt length, you may have to repeat the process as you drill deeper.

The copper clad carbon rod, 1/4" is a good size, can be bought at any welding supply store.

T_Bone

This might not be the right thing to do, but I've done it a few times with what seems to be success. I simply drill the stud with a slightly larger drill, tap the new hole to fit the slightly larger stud, drill the hole in the manifold to accommodate the slightly larger stud, and pretend like that was the size that was in the head in the first place.

It's a whole lot easier and less time consuming.

Good luck,

Tom in TN