Quote:
Originally Posted by Gray Adams
I don't have any problems (on a Haas with rigid tapping) with cycles or directly written programs, cut taps or roll taps. As long as its properly cooled, programmed, and you're not trying to go too deep at once, it comes out fine.
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Perhaps your Haas is tighter than the Fadal and Okuma machines my bad experiences came from. I should revise that I never had a problem with 1/4-20 or larger, but smaller than that with either blind or deep through holes is problematic for most machines. Insufficient chip evacuation was the typical cause of seized and then broken taps. Lots of small holes are tapped by NC machines in production, every day. Those parts, programs and fixtures have been optimized for production.
I still maintain that for prototypes and student projects, it is far better to tap by hand. It builds character and an appreciation for the material and tools. It also keeps you from finding out how deep is too deep, especially when you may be working with an unknown alloy. A bit of a tangent, but not all aluminum cuts the same. Once had a college robotics team grab some 3003 (essentially pure Al) when they ran out of 6061, for an intricately cut CNC'd part. Had to slow the spindle to half, and feed to a third of the rate for 6061 to get passable parts. Machine tapping was not an option because of the "grabby" nature of 3003.
-- Len