Help! > Mistakes, muckups, and dangerous behaviour
Strange broken drill
Roger B:
I was drilling a deep (40mm) 3mm diameter hole in my CI cylinder head using what the local shop call stainless steel drills. This one was quite happy chewing it's way through the lump of P20 mould steel I used for the ER chuck and most other things I had tried it on.
I was regularly withdrawing it to clear the swarf, but when I got to 35mm it suddenly stopped :o The shank had twisted off at the end of the chuck :toilet_claw:
The remaining part was easily removed with a pair of pliers and is still useable ( if slightly shorter ;) ) I finished the hole off with normal 3mm drill without any problems.
Any ideas what happened?
b.lindsey:
Not the usual place to break I agree Roger. Perhaps it was either a faulty blank or prior use had somehow fatigued it in that area. Good that you were able to extract it though.
Bill
Jasonb:
Did the hole wander?
Roger B:
Not significantly. When I replaced the drill it broke through as expected into the water passage at the base of the cylinder head. I would estimate less than 0.2 mm deviation in a 40mm deep hole.
My first thought was that it had jammed in the hole, but I was able to twist it back out easily with a normal pair of pliers. These drills seem to have finer pitch than 'normal' drills (and also cost a little bit more) :headscratch:
derekwarner:
This is also a 3.0 mm drill & stamped HSS :lolb: .... was used in a drill press with a keyless chuck...& drilling through 2 mm sheet steel that was adequately clamped........
My only thought was that they popped out @ lunchtime to get some fried rice :ChineseBow: & forgot about the heat treatment process...... Derek
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