Quote:
Originally Posted by ptc
Dan I know you have had alot of advice on your bolt hole already, but I have always had the best luck just drilling it out first with a centering drill (available at machine shop supplies or McMaster Carr)- its a small drill head that gets a center punch drilled perfectly. Then use a small drill (pilot drill) to go through the old bolt.
Youre using 5/16-18 bolts for the seat mounts, so something about 1/8" should work - use a new sharp drill bit and let the drill do the work -DONT FORCE IT THROUGH.
THen use a tap drill for 5/16-18 to go through the the pilot hole. Then just run a tap through the hole. Get a new tap drill and a new tap. they cut much better. The tap is hard enough to get the bolt bits out.
For the broken drill bit -get a carbide cutting bit. It will drill it.
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A centering drill, huh? Never heard of them before. Thanks for the head’s up BUT that ship has already sailed. I already drilled all the way through the first broken bolt and of course it’s NOT centered as it should be. I always wondered how guys could center punch a bolt broken off flush or below the surface because they never break off cleanly.
At this point my options for the broken drill bit are either a burr on my die grinder or drilling around the broken bit with a smaller drill to loosen it enough to grab it with needle nose pliers.
If JJ is right^^^ that the underside of the anchor plate is visible from below then I will drill UP through what remains of the bolt and use a punch to get the bit out.