Re: [CAD_CAM_EDM_DRO] Using a tapping attachment with a CNC bore cycle

On Fri, 15 Feb 2002 06:38:16 +0000, Jon Elson <elson@...>
wrote:

>I just used the RPM as stamped on the milling head nameplate, plugged it
>into a formula, and used that for the feedrate. It worked superbly, and the

So you are tapping at 1,000 rpm or more? Eeeeeee Haaaaaa! Cowboy Up,
Hang on and nod. Is there a buzzer after 8 seconds? <G>

A 1/4-20 tap at 1,000 rpm would require a feed rate of 50 in/min. My
mill has a max feed rate of 40 in/min so I think I'll have to reduce the
rpm. I was thinking of tapping at more like couple hundred rpm. Should
I be planning to tap at as high an rpm as I can and still be within the
feed rate constraints? That's a scary thought at the moment. I do
nearly all steel. I've been tapping at 80 rpm in the manual mill - my
aging reflexes aren't up to anything faster. I need to free myself from
the constraints of manual machining for tapping?!?

OK, tooling update (gloat?). I just bought another tapping head on
Ebay, a Tapmatic N/C R-1, that goes from #10 to 1/2", new in the box,
for 27% of its new cost. See

http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1702558223

if your interested. Sort of excited about this one - I do a lot more
holes in the #10 to 1/2" size range. The NMTB40 adaptor fits The
Animal.

Anyway, I am going to be machining a couple of aluminum blocks to make a
coolant pipe fixture for my lathes (and for the manual mill) that will
have some tapped holes including two with 1/8"npt. (The aluminum block
for use on the lathes will bolt to the top of a real cheap import
magnetic dial indicator base replacing the useless plastic block that
came with it.) I could hand tap the pipe threads but might just
experiment since that is in the size range for the new tapping head, and
there will be two such holes side by side - the vary thing CNC machines
are supposed to be good at. I'll machine some air and make sure the
depth is right on before going for the chips.

>only 2 taps I've ever broken with it were caused by feeding too DEEP, not
>by feed getting ahead of the spindle revolutions.

I hear the too deep. That concerns me also. Since the CNC tapping
attachments don't have a torque relief, that requires careful thought
when setting up the program.

Thanks
Fitch