Re: [CAD_CAM_EDM_DRO] Re: Rigid Tapping--How is this accomplished?

Thanks for the tip about the spindle brake. Our mill uses a VFD on
which we can adjust the deceleration. I'll turn that way up if we use a
floating tap holder. I was worried about spindle coasting. With a
coarse thread, ie 10 TPI, one doesn't get many turns with 0.5" of
compression.(5 to be exact...)

The thing about coarse threads is that they are usually on large
diameter holes and I can use thread milling to cut those threads.

Kim

On Mon, 2003-10-20 at 10:32, doug98105 wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> I just can't fathom how one could drive a tap from the
> > top to the bottom of the hole without reversing it and without
> breaking
> > it.
> >
> > Kim
>
> Kim,
>
> Try using thread forming taps. No chips. But you have to be
> careful of the tap drill size.
>
> Since the threads are formed by displacing material from the hole
> diameter to create on-size threads you need to make sure the hole
> size is held within a much closer tolerance range than for a cutting
> tap. Threads are measured by pitch diameter and percent of thread.
> A .001" difference in hole size can make a significant difference in
> percent of thread with smaller thread sizes. Sometimes there may
> not a drill of the theoretical size available so reaming the hole to
> size is an option.
>
> A tension/compression holder works well for mill tapping. Calculate
> the needed feed rate based on spindle rpm and tap pitch. Run a test
> in soft material to verify (soft plastic is a good choice).
> Depending on how fast your spindle reverses you may need to account
> for spindle "coasting" once the programmed depth is reached. Some
> mills are setup with a spindle brake that's energized on an M05,
> this helps hold accurate depth.
>
> Here's how I program the process:
>
> G97 M03 Sxx Txx
> G00 Xxx Yxx Z.1
> G01 Z-.50 Fxx
> M05
> G01 Z.1 M04
>
> On my mill the M05 brakes the spindle.
>
> Doug
>
>
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Kim Lux <lux@...>