will give it a try

WHen I made the disc for the BP here I used a 50% factor for the on off. THere ended up being half the disc cut away. It reads precisely as fast as the spindle will run 5000 rpm.

That was with using the LPT port driver.

(;-) TP

Mine used the OPB 917B opto and the disc was about 90mm OD with a 10mm slot and it worked fine up to, if I recall, 5000 as well. I usually never went above 4000 on the BP but I did test by cranking up the VFD.
On the lathe I think it was again a 10mm slot but only a 70mm OD disc, the lathes top speed was only 2000rpm however but again it worked well.

Hood

I have no intention of throwing a blanket over this whole discussion becasue it is educational in finding out how to hook up an RPM indicator. BUT:
If you look at the video from Tapmatic - and from my experience doing it manually - as long as you are only tapping a hole maybe no more than a half an inch deep or so, all you need to do is set the tap into the hole. The tap will screw itself into the hole and the spindle of the tapping head will automatically extend by itself as the tap screws in. When the tap reaches the bottom of the blind hole the head internals will slip until you get aroud to lifting up on the tapping head. Then it will go into reverse unscrewing the tap.

With that said I figure all you need to do is emulate the action you take when doing it by hand. I.E. do a G1 down to a depth enough to get the tap into the hole to get the thread started. Then perhaps feed down very slowly a very small amount just to waste some time until the thread is complete. Then retract the head again quickly to ensure the tap is above the work. The tapping head knows how to do the job for you. I don't think you need to down-feed at any particular rate to follow the tap. That only complicates things. (it may depend on the type of head you have - not sure but mine works as described).

BTW andy_con.

There is a tension adjustment on the tapping head that ensures it slips if the tap binds up in the hole (or when it runs into the bottom of a blind hole). If you have that set too tight that might explain why you broke so many taps.

Just my 2cents worth - sorry for the interruption - now back to the discussion.

Sage

The clutch is a safety NOT a means to run the taphead. UNTIL you apply downpressure you will not engage the clutch that drives it down AND until you apply UP pressure it will not reverse itself and retract the tap.

Ideally I always run a touch of overfeed to insure good pressure on the clutch. Same with retract do the initial retract to set the clutch at MAX speed (G00) then feedup the rest of the travel. The idea is to get the tap retracted and NOT have a lot of excess spring pressure at the point  just before it clears the surface to prevent it springing up and tearing the last thread or so.

Being it is a floated design it is not really RPM sensitive as long as you are close to what you tell the machine it actually is.  IF you are off a few rpm it is not a big deal to the taphead.

Tapmatic GIVES you the proper sequence to follow for CNC use.

Just a thought, (;-) TP

ok spindle feedback fully working. all i had to do was connect gnd to pin 25 of the parallel port.

but i have snapped 4 taps tonight

OK HOW it it snapping taps overfeed under feed overretract moving OFF center before it is done ? are you using a tapping cycle or remming cycle or hand coding it. Are you getting a pause from mach during the cycle? Are you bottoming the tap ?

Drill size to small ?

Wrong H factor for hole size ?

Not using proper tapping fluid for application?

Can you describe what takes place that snaps the tap?

(;-) TP

BR549:

You are exactly correct. I've only used my head a couple of times and as usual my memory did not serve me correctly.
Things happen so fast in the video I guess I was seeing whatever supported my memory.

Sorry for the interruption.

Sage

NOT a problem I HAVE used the clutches a time or two (;-). But you have to be careful of the settings as IF it slips too much then you end up at the top of the retract BEFORE the tap clears the hole and when you move off it snaps the tap.

Proper tap for the application also plays a big role. Spiral fluted, spiral point botton tap, rollform tap. ? thru hole blind hole ,shouldered hole, recessed hole.

Chips can be a BIG problem with small taps.

(;-) TP

http://www.youtube.com/watch?v=ZGMC55t-98E

how do they tap so fast and go from one hole straight to the other without any swarf on the tap??