drilling holes and hard plate

admin

will any type of bit last in hard plate? we use alot of hard plate say 400 and 500.i currently just burn the holes.
Reply:Cobalt high speed steel bits work pretty good but it is not something you want to do every day.  Sharp bit, flooding coolant, slow speed, and lots of power on the drill press.I was given a job about a month ago to countersink flame cut holes on inch thick 400 Brinell.  Even carbide failed.  I managed 8 holes deep countersunk in 8 hours and countless broken inserts.If flame cutting works for you I would be inclined to not change.
Reply:I drill Hardox 400 with Viking ultra cut super premium drills I believe Fastenal carries them. Slow Slow Slow rpm, lots of feed pressure & plenty of cutting fluid. I drill 1" plate with 1" holes using the reduced shank bits with no problems.
Reply:Another trick that I have not tried is to anneal the local area.  Apparently you heat a silver dollar size to a red then let cool slowly.  The area will be much easier to drill.  I have not tried this method myself but it sounds reasonable.
Reply:Not all carbide drills are the same. Some shouldn't be used on steel. Give the folks at MSC a call, tell them what you're trying to and they'll get you what you need. http://www.mscdirect.comLast edited by tresi; 04-16-2007 at 09:13 PM.