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Old December 13, 2010, 01:48 AM   #6
HiBC
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Join Date: November 13, 2006
Posts: 8,272
Begin with a center drill.When you drill through with your tap drill think about what is happening with the cutting edges as they break through the threads.You will help if you can control the downfeed of the spindle so the drill isn't suddenly fed too big of a bite.If you run the quill depth stop up so you stop against it as you are drilling,you can roll it a little with your left thumb,feed to the stop,chip break,roll the stop a few thousandth more,etc.
If you lift the drill out,blow the chips out of the hole before you go back in.A chip spinning around in front of your drill tip is a problem.
As a drill is breaking through,the steel before the center tip of the drill gets very thin,and cutting geometry is less ideal in the center of a drill.

Like the primitive fire bow,heat can build quick as the steel thins.Some steels will suddenly get very hard.So,as you are about to break through,add some oil for coolant.
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