10-03-2012, 06:25 AM
Hand taps have no chip control geometry, such as spiral point or spiral flute, which machine taps do have. As such, you have to reverse direction every 2 or 3 turns to break chips.
The number of flutes increases or decreases load "per tooth", though less flutes makes for a stronger tap. More flutes helps carry chips away better. I practical terms, you notice no real difference in how much pressure it takes to cut the thread.
NEVER use a hand tap for power tapping. You want to do a power tap cycle in one pass, and hand taps need that chip-breaking reversal every couple of turns.
Yes and no. If you have really abrasive material or have to do lots of holes, coatings help. There are TiN, TiCN, THL and more. The right coating can make all the difference in the world when you need to get it done. Rarely is this an issue in most home shop situations.
The number of flutes increases or decreases load "per tooth", though less flutes makes for a stronger tap. More flutes helps carry chips away better. I practical terms, you notice no real difference in how much pressure it takes to cut the thread.
NEVER use a hand tap for power tapping. You want to do a power tap cycle in one pass, and hand taps need that chip-breaking reversal every couple of turns.
Yes and no. If you have really abrasive material or have to do lots of holes, coatings help. There are TiN, TiCN, THL and more. The right coating can make all the difference in the world when you need to get it done. Rarely is this an issue in most home shop situations.