I did a fair bit of small tapping (4-40 to 10-32) with a Procunier "CNC"
tapping head. I started out slow, and eventually worked my way up to
around 1000 RPM. That was mostly in aluminum. I now do rigid tapping on
the mill, and also do it around 1000 RPM. Results are great, and the taps
seem to last forever. I use "alum-tap" as a tapping lube, it is
If you are cutting at 2,000 RPM, that is 33 revolutions per second. If
it takes 0.5 seconds to stop the spindle, this is roughly seven
revolutions beyind the point where spindle just starts
decelerating. Quite a lot of overrun.
For now, I tap everything at 500 RPM.
Largest I tapped was 1/2"-13 in aluminum, at 500 RPM. The Bridgeport
Interact 2 did not even blink.
Thanks guys. I was thinking something like that. Se the HF DP at a
moderate speed and leave the tapping head in it all the time. Even at 500
RPM its so much faster than hand tapping that I doubt I'll worry too much
about it anyway. I also ordered some spiral flute taps in the sizes I
figured I'ld use most.
Any tell tail signs that tell you its time to retire a tap before you ruin a
work piece with 20 hours of machine time invested in it?
Depends on the tapping head you have. The TapMatic 30X for
example, has a torque limit clutch. The proper way to set it up is to
set the torque to minimum, then (with a brand new tap, and the same
workpiece material that you will be tapping), increase the torque until
it just provides enough to tap on through. Leave it at this setting
(for this size of tap and workpiece material), and when it starts
slipping again, it is telling you that the tap is dulled enough so it is
time to replace it. I don't know whether the Procunier tapping heads
have the same feature -- and only *some* of the Tapmatic ones have that.
My smaller one (up to #10 taps) has the feature, the larger one (good to
at least 1/2") does not, but had an adjustment to how much travel before
the dog clutch releases -- for when you are tapping shallow blind holes.
I wish that both heads had both features -- but I've got to live with
what I got for cheap prices. :-)
Not that this is helpful except for general information purposes, but the
SPD series (3,5,7 and 9) do not have a clutch.
Never had a problem with them, but I really like your description above on
how to set the machine so I may look into those other heads a bit more now.
Joe Agro, Jr.
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
Production Tapping: http://Production-Tapping-Equipment.com /
Flagship Site: http://www.Drill-HQ.com
If it is a Tapmatic, the clutch (if present) takes the form of a
knurled ring at the top, and a white band partly covered by the top
exposing a spiral list of numbers (relative torque -- not to any
particular units -- or even to the tap size number. Just something to
remember about where you had it set last time as a starting point.
Hmm ... that would require the operator to be a bit more
observant when running a bunch of taps in parallel, since I don't know
what would happen when one started slipping and the other five (or
whatever number of spindles you have) kept feeding. :-) I guess that
they would stop fairly quickly when the dog clutch disengaged, but the
operator might not notice that he had not reached the full depth,
leaving a problem for inspection to catch.
O.K. In that case, you would need a stronger tapping head to
handle the extra torque which the four taps in parallel would produce.
And -- I suspect that it would be a bit less sensitive to a single tap
dulling, so you would want to replace all four taps at once when it
started to slip.
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