I hate to admit that I had anything to do with this, but when I and my friends at the shop were all young and foolish, one of the guys broke off a 5/16 drill bit in a deep hole into the end of a roughly 4" Dia. shaft.
About a half inch was protruding from the shaft, so he tried to get it out with vise grips. He made about another half inch of progress in working the bit backwards out of the hole before the bit broke again, this time well below the surface. It was a large industrial gearbox shaft and he had it all finished except for the grease channel he was trying to drill. Rather than scrap the expensive piece he decided to do something rather foolish to salvage the project.
We gathered the 2 broken pieces of drill bit that we had and added the lengths together then comparing that to a complete bit that size. This showed us that the hole was deep enough in the shaft if he fudged a bit on the location of the cross drilled hole where the grease would eventually come out. He went ahead and cross drilled the shaft in that location, threading the outer end of the hole for a short depth for a bolt thread temporary plug. Then he drilled a fuse hole thru the center of the bolt. You can see where this is going can't you?
The following morning, he used a splinter of wood to pack the cross hole with black powder. He carefully screwed the bolt finger tight into it's hole and pushed a piece of cannon fuse into it. With the shaft laying across the pan of his lathe and with the offending end pointed toward the roll up door, he lit the fuse and we all ran for the doors.
It was noisy, but not as much as I had expected. There was some funny smelling smoke in the shop for a little while 'til we aired it out and a broken drill bit driven almost all its length thru the roll up door (which was made to quickly disappear), but within a couple of minutes no one could tell anything untoward had happened.
And yes the shaft was salvaged. I do not recommend this unsafe action to anyone!!!
About a half inch was protruding from the shaft, so he tried to get it out with vise grips. He made about another half inch of progress in working the bit backwards out of the hole before the bit broke again, this time well below the surface. It was a large industrial gearbox shaft and he had it all finished except for the grease channel he was trying to drill. Rather than scrap the expensive piece he decided to do something rather foolish to salvage the project.
We gathered the 2 broken pieces of drill bit that we had and added the lengths together then comparing that to a complete bit that size. This showed us that the hole was deep enough in the shaft if he fudged a bit on the location of the cross drilled hole where the grease would eventually come out. He went ahead and cross drilled the shaft in that location, threading the outer end of the hole for a short depth for a bolt thread temporary plug. Then he drilled a fuse hole thru the center of the bolt. You can see where this is going can't you?
The following morning, he used a splinter of wood to pack the cross hole with black powder. He carefully screwed the bolt finger tight into it's hole and pushed a piece of cannon fuse into it. With the shaft laying across the pan of his lathe and with the offending end pointed toward the roll up door, he lit the fuse and we all ran for the doors.
It was noisy, but not as much as I had expected. There was some funny smelling smoke in the shop for a little while 'til we aired it out and a broken drill bit driven almost all its length thru the roll up door (which was made to quickly disappear), but within a couple of minutes no one could tell anything untoward had happened.
And yes the shaft was salvaged. I do not recommend this unsafe action to anyone!!!
