Posted by Chris Case [108.225.237.77] on Wednesday, August 05, 2015 at 11:07:03 :
In Reply to: Drill Bits OT posted by The Dodge Boys [173.49.177.213] on Wednesday, August 05, 2015 at 10:39:35 :
Cutting speed x 4, divide by the diameter.
Cutting speed of steel is 100 feet per minute. Times 4=400, divide by the diameter, say 1/2",= 800rpm. Then a skosh slower. Most drill motors don't go that slow, or have no power if they do. For that 1/2" hole, I would use progressively larger bits to get there to make up for the lack of power. 3/16, 3/8, 1/2.
And ease off the pressure as they break through, or run the risk of chipping the bit.
Lots of car parts are a bit harder than mill steel, and may need to go half as fast.
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