Still not quite sure I understand. So it cuts 1/2 fills 1/2?
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I watched the video. I'm still confused on what thread forming is compared to tapping. Is material added in the small voids?
We do a lot of thread forming at work. During normal thread cutting, one drills a hole to the minor diameter. Minor diameter is typically calculated as major diameter minus the thread pitch.
Example 1/4-20 cut thread:
20 threads per inch has a pitch of .05” (1 / 20 = .05)
The minor diameter is calculated as the major diameter minus the pitch (1/4” or .25” - .05” = .2”)
Thread forming displaces the metal instead of cutting it away. Displacing metal hardens the surface and produces a stronger thread. The initial minor diameter is larger and is usually calculated as the major diameter minus 1/2 of the pitch. Whats cool about forming thread is as the form tap enters the hole the metal is displaced from the major diameter and forms the minor diameter to be basically the same as a cut thread when finished.
QuicksilverJK questioned if forming cuts half and fills half. That close, but no cutting, it’s more like half is displaced into the other half.
Example 1/4-20 formed thread:
Again 20 threads per inch has a pitch of .05” (1 / 20 = .05)
The minor diameter is calculated as the major diameter minus the (pitch / 2) or 1/4” or .25” - (.05” / 2) = .225”
Now before you read all this and say I’m going to buy a bunch of form taps for my toolbox, form tapping requires an incredible amount of torque and power. It cannot be done by hand!
I’m ready to accept my nerd award now. [emoji849]