A few questions about a reverse tapping head.

[l u k e]

I purchased a reverse tapping head awhile back haven't had the opertunity to use it yet. I have a job comming up that I would like to give it a try on. I'll be Form tapping 5/16 threads in 6061 at 5/8" long and through hole.

Is the "stop" just to limit the manual down stroke of the spindle by the operator, so the internal gearing in the head can take over? At first I thought it was to limit the spindle so the tap would not run through the work peice.

How do you keep from running the tap all the way through the hole?

What RPM should I be running?

[msomerville]

You need to have some sort of stop set up so that when you bring the quill down against the stop the head takes over. The one I use has about .200 of travel so I set my stop .200 shy of where I want to be. When the tapping head reaches the end of the stroke it should disengage (neutral), and then start to pull up on your handle to automatically reverse the direction of the tap.

[handlewanker]

Hi Luke, If it is the same as the one I've got you feed the tap into the job maintaining a gentle pressure downwards to start the tap cutting, and when you have reached depth, start to pull back, again gently, or you'll pull the tap out of the collet. As you pull back the internal mechanism reverses the tap and you just follow it out. The stop ensures you don't go pressing all the way down. As you hit the stop, spindle down feed will stop but the collet holding the tap will pull out and reverse the tap and start to back out, now you just follow it back keeping pressure off as it self feeds out.
Ian.

[l u k e]

OK cool that makes sense.

What RPMs would you suggest? Low or high? I've never done form tapping before so I'm not sure where to start.

Also, letting the tapping head bottom out and disengage may be a problem, because the tap is likely to go all the way through. The only way I see to deal with it is to just "eyeball" it. I just don't want to end up with partial threads in any of the parts.

[l u k e]

Originally Posted by msomerville You need to have some sort of stop set up so that when you bring the quill down against the stop the head takes over. The one I use has about .200 of travel so I set my stop .200 shy of where I want to be. When the tapping head reaches the end of the stroke it should disengage (neutral), and then start to pull up on your handle to automatically reverse the direction of the tap.

I reread this and think I misunderstood the first time. Were you saying that you know how deep the tapping head will tap before it disengages, and based on that it tells you where to set your stop in relation to the depth of your threads. (So you won't run the tap all the way through the work piece) Yes??

[handlewanker]

Hi, as you're through tapping then a spiral point or gun nose tap will be used. These throw the swarf forward and out of the bottom of the hole.
Speed would be about 250 to 300 rpm, in alluminium or steel. If you go faster you'll risk losing control of the taps progress at the moment of change over.
Plenty of cutting oil, not the soluble oil/water compound, applied to the tap or to the holes prior to tapping.
The stop is just a help to stop going straight through, as when the spindle hits the stop the tap still continues for a bit and you then pull up and it will back out. It just takes a bit of co-ordination.

[l u k e]

Thanks guys.

[msomerville]

Yes you know how far the tapping head travels before it disengages. That will enable you to set your depth. Say you only wanted to tap .75 deep, set your depth at .5 or so maybe even less if you are unsure of the travel, so when the head disengages you are .75 deep.

[l u k e]

Is there a easy way to measure the depth of cut on the tapping head?

[msomerville]

Not that I know of. Trial and error. I would stop short of the depth and work up from there (or down depending on how you look at it). Just start off with enough travel to get the tap to engage and check your threads after that.

[l u k e]

I'll figure it out.

Thanks for all the info.

[Ben Colby]

With the machine spindle off, pull the collet holder of the tapping head down and twist it clockwise.
Release it and it should stop before fully retracting, ie it will feel as if its resting on a shelf before going all the way back up. This spot is full depth or
full Z travel of the tapping head.
Here's the procedure:
1) install tap into tapping head collet.
2) Pull collet down and twist clockwise, then release to catch Z travel full depth position. If it goes all the back up to the top try again until it catches.
It's real easy to feel once you have done it a couple times. If you turn it
counterclockwise by hand it should spring up to full retract postion.
Once you pull it down and twist it to get you full Z travel depth on the tapping head itself, you are ready to set your tapping depth.
3) With the machines knee or quill set your required depth.

Your tapping head should have a maximum speed for RPM. DO NOT exceed
that RPM for any reason. Tap aluminum as fast as your tapping head and
machine will allow. Start slow and speed up as needed for production versus
accurracy. Use plenty of oil or tapping fluid for all Roll Form taps. Do not drill
oversize holes for FORM taps.