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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
I once in my machinist career had to tap blind holes for some small screws in H900 17-4PH stainless. I broke the first several I tried by hand tapping. I was building the part on a CNC machine. One could set the spindle to stop at a given depth & reverse rotation. I calculated the feed rate to accommodate the spindle speed in relation to threads per inch. I then proceeded to "Power" tap the rest without breaking another tap. I have tapped hundreds of holes by simply chucking the tap in a drill chuck on a Bridgeport mill & hand feeding by feel. This works great on a through hole, but not so well for a blind hole. We used a lot of two flute taps which had the lead ground to curl the chip ahead of the tap, which was called a "Gun Tap". This designation had nothing to do with firearms, but because they were designed for power tapping. You can actually power tap under conditions which are near impossible to tap by hand. You can believe it or not as you see fit but with over 35 years in machine shops, I tapped a "LOT" of holes both by hand & by power.
Miller/TN I Didn't Say Everything I Said, Yogi Berra
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Joined: Jan 2002
Posts: 13,146 Likes: 1146
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 13,146 Likes: 1146 |
...... we have all shoved a tap in a hand drill at one point ....... Not I, never. I know how to power nap, but not power tap. SRH
May God bless America and those who defend her.
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
I have never Power Tapped with a hand drill either. I try my level best to not tap with an un-guided tap, only do that when it is an absolute necessity. If I drill the hole under a drill press then I will put some type of guide in the press to keep the tap aligned. In spite of the lead-in, taps are not self-centering, plus support for the upper end gives one a bit of a hedge against breakage.
Miller/TN I Didn't Say Everything I Said, Yogi Berra
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