On Mar 13, 12:03*am, Ignoramus25538 ignoramus25...@NOSPAM.
25538.invalid wrote:
My CNC mill does rigid tapping and it is great and easy to do -- just
one "one liner" like this

* * G33.1 Z[-0.5] K[1/24]

would rigid tap a 24 TPI thread from the current point to the depth -0.5.

Easy and powerful.

It even works great with fine threads, but I have a problem with
coarse threads. I hold the taps in a Jacobs drill chuck. The chuck
cannot hold a coarse tap, like 1/4-20, the tap slips in the chuck. The
result, is holes that are partially tapped and a slipping tap. Not the
end of the world, but I want to do better.

What kind of tool holder should I use for this rigid tapping? Would
colleted tool holders help with this?

i

sharpen the tap
how?
on the inside edge of the flute, just a touch- make the cutting edge
(teeth) dead sharp again.
Its best to have a foot controler for your mounted dremel with a
larger dia. stone grinding wheel. Hold the tap with inside of flute
lined up with on the square edge (corner) of the (stopped) wheel, then
turn it on with your foot pedal.
Just a touch on all flutes- following the same shape the factory
inside angle, makes a B I G difference on used taps that like to slip
in drill chucks.
I use a thicker cut off wheel in a stationary mounted Du Moore.
A drill chuck with the jaws in *good* shape should have no problem
driving upto a 1/2 tap w/o slipping for general "g-job" use.
If it does slips or push up/ down in the chuck in a CNC, there may be
a timing issue with the axis/spindle synchronization.

--

~g~