I have two sets of Chinese made Zirconium Nitride bit sets one I bought about 3 years ago at Costco. I think it has Master Grip printed on the front and another I just recently purchased at HF. Both sold for around $50.00us and appear to be the same bits. They have approximately 100 bits in fractions, wire gauge and letter gauge. Very handy for matching taps with drills. The Master grip set has been very durable and the bits stay sharp for a long time. I drilled 112, ¼” holes in 1X2” steel bar for a shelf pin hole guide. I also have a Dewalt set that has not been as durable as the Chinese made drills. The Chinese drills are all different lengths, if you compare different sets next to each other the drills of the same size will often be different lengths. I believe these sets are made up of industrial drills that have been re-sharpened and re-coated. Not sure but it makes sense to me and would explain the high quality steel at such a low price. As said above speed is very important, slower for larger dia and faster for smaller. Plenty of coolant/lube for steel. Aluminum is not a coolant critical as long as the bit is sharp and cutting in new material each revolution.
Paul
Paul
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