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

"Fitch R. Williams" wrote:

> On Fri, 15 Feb 2002 19:00:48 +0000, Jon Elson <elson@...>
> wrote:
>
> >You'd better check the spindle HP requirements before tapping a 1/2 - 13
> >hole in steel with a tapping head.
>
> I was thinking I'd be OK. My reasoning - its a 3hp mill, running at
> say 80 rpm - that should be around
>
> (5252*3)/80 = 197 ft-lbs of driving torque. Even with 60% efficiency in
> the drive train that still gives over 100 ft-lbs to drive the tap.

Yikes, 3 Hp at the lowest backgear speed! I did my tapping in direct
drive, on the lowest speed.

> I've done 1/2-13 by hand - and it doesn't feel like it takes 100 ft lbs.
> Is there a factor I'm missing that's going to sneak up on me? Usama bin
> TorqueFactor?

Well, I don't know about this particular tapping head. That seems like a
LOT of torque, though. But, I suppose the 1/2" rated tapping head must
be designed for it.

> The 1/8npt was to be in aluminum. I've done that by hand in times past
> with a straight drill - I'll give it a try when the time comes and make
> a report. It's clear I need to be sure I program and tap to the
> specified depth accurately.

Aluminum should not be much of a problem, unless you drive the NPT
tap real deep. The deeper you go, the higher the torque required.

Jon