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Black85vette's post about problems machining drill rod is reminiscent of a problem I had yesterday. In my lathe, I had drilled a 7/64" hole axially though the center of a piece of 3/16 drill rod for the valve tube on my opposed 4 cylinder air engine. When I pulled it out of the collet, it was blackened in the middle, obviously from overheating in the boring process.
Then I put the tube inside the valve body and clamped it all up in the drill press so I could drill the radial holes that would let the air pass out to cylinders as the tube rotated. When the 3/32" drill bit hit the tube, it stopped cold. There was no cutting action at all. Hmmm, I must have tempered it when it got hot during the boring process. I took the tube out, sat it on the vice and heated the whole thing cherry red and let it cool slowly to remove the temper.
I clamped the assembly back into vise and lashed it all down on the drillpress table. Fired up the drillpress, brought the bit down into the work and.... same thing, wouldn't cut! I backed off and scratched my head a bit, then I noticed that I had the depth stop set on the drill press. :-[ That was what was stopping the bit. Loosened up the depth stop, and all went well from there, well, except I drilled the holes in the wrong place and had to remake the piece from scratch!
Chuck
Then I put the tube inside the valve body and clamped it all up in the drill press so I could drill the radial holes that would let the air pass out to cylinders as the tube rotated. When the 3/32" drill bit hit the tube, it stopped cold. There was no cutting action at all. Hmmm, I must have tempered it when it got hot during the boring process. I took the tube out, sat it on the vice and heated the whole thing cherry red and let it cool slowly to remove the temper.
I clamped the assembly back into vise and lashed it all down on the drillpress table. Fired up the drillpress, brought the bit down into the work and.... same thing, wouldn't cut! I backed off and scratched my head a bit, then I noticed that I had the depth stop set on the drill press. :-[ That was what was stopping the bit. Loosened up the depth stop, and all went well from there, well, except I drilled the holes in the wrong place and had to remake the piece from scratch!
Chuck