On Tue, 14 Dec 2010 08:23:28 -0700, "Bob La Londe"
wrote:

I've got this urge to own a tapping head, so I've started doing a little
reading on tapping speeds. One formula I have read is:

For inch taps
RPM = SFM / (.26 * Tap OD)

http://www.newyorktwistdrill.com/tap...l_data_03.html

A middle of the road SFM for aluminum ( I know it can vary dramatically
depending on hardness, alloy, etc ) is about 600.

When I plug that in for a 1/4" tap it comes up with 9230.769 That seems
insanely fast to me. Are you guys who do this really tapping holes in a
fraction of a second?

Seems like for small jobs the clamping and positioning requirements to do
that would take longer than tapping a couple holes by hand.



Obviously, I do it in a NON home shop enviroment, but in
aluminum....6061, for example, I'll run at between 600 and 800 RPM
with flood water soluble coolant.

For a REAL production run....a few thousand holes, I'll set up the
reversing tapping head on the VMC and spin that at about 2500 RPM

But that is just me....your mileage may vary

Mike