Roll Taps (Flute-less Taps)

[Doozer]

The threads made by roll-form taps roll a burr and make a thread that is easy to cross thread when being assembled.
I never allow roll-form taps on any prints that I generate. Just leads to assembly troubles.

-Doozer

[projectnut]

Thanks for the link to the thread forming tap chart. I've been using them for several years and have to go through the math each time I use a different size. I try to keep a record of the sizes needed, but haven't done as good a job as I should. I've researched for hours at a time trying to find a wall chart or something that could be printed into one. All I seem to come up with is the standard thread cutting tap charts regardless of the search terms I use.

I'll be taking either a printed or electronic copy of this chart to a local shop to get a couple copies printed. Thanks again.

[Dan Dubeau]

Also known as thread forming taps. They actually "form" the thread instead of cutting it. Stronger threads, and stronger taps that last much longer in production machinery than traditional cut taps. I've been using the same 1/4"-20 form tap in our haas' at work for about 5-7 years now (can't remember when I changed it), and the number of holes it's tapped has got to be in the 5 figure range. They can be picky about starting hole diameter, so be careful of that. They need a bit bigger hole to start with than a cut tap. For the 1/4"-20 I use a #1. There is information out there, but it's not usually contained on the normal machinist thread charts in circulation.

Here's the first google search I did. https://kar.ca/pdf/REFERENCE_TapDril...ps_oct1217.pdf

[Tungsten dipper]

What are they used for? Any background or information would be appreciated.