Power tapping - what do you use to hold the tap?

[JRouche]

Yeah, I think I screwed up paul. Keith talked about spiral taps, I automatically thought full on spiral tap knowing Keith is a good Machinist. I didnt know we were talking about the puzzy taps for those that cant find the hole.

No really, that is all those half azzed spiral pointed tips are for. They are good, they work great. I got confused. I was thinking about full on spiral taps which are cutting beasts. JR

[Bob Engelhardt]

In the case of runout, one would have a case like this (tap held in tailstock):

[...]

[...]
It is like forcing a twist drill bit to cut sideways, against the margin behind the edge of the flute, on the OD.
[...]
And the tap's shank will bend somewhat and ultimately break before the tap actually cuts sideways to any great extent.

You're right! And the drawing is misleading: the 1° angle is only at the start of tapping. As the tap travels in, the angle increases to the breaking point. Which has never happened to me using my certain-runout T-handle wrench.

I still like the idea of a modified Tee handle tap wrench for holding taps for power tapping.

It has served me well. None of my chucks hold worth a damn.

[mikey553]

I looked at the key for my 16N today and it's not marked as a K4. The only marks I could find were # and 9
with the # over the 9 (it could be a 6 with the # underneath). I measured the key and the dimensions are:

Pin diameter: .3695"
Body diameter: 1.037"

The body has 12 equally spaced grooves. Hope this helps...

Thanks Keith. I have several Jacobs K4 keys and all of them are marked with "K4" and "4" inside a square. The dimensions are close to what you measured.

[oxford]

Several posters mentioned keyless chucks..... Not good IMO because they loosen when run in reverse.

I am one of those posters. You are right, they can and it has loosened on reverse. They could also self tighten on their own when going forward.

With that said, I have tapped hundreds of holes with a keyless chuck in the mill. I don’t feel either of those points are worth worrying about. Sure if you have a choice, don’t use the keyless. If it’s all I have or already in the machine, I’m not changing it out for something else.

[mikey553]

Runout is important in a tap mount? Did you try to actually tap a hole with that tap? I have tapped holes with taps held in Jacob's chucks which are infamous for poor runout. It worked perfectly, with some caution on my part, of course.

A tap should be free, at least free enough to follow the hole. If the rear end of the tap is close to the axis used to drill the hole, then the front end of the tap will/should center itself on the hole at first contact. After that it should work, hopefully without breaking.

So, I am still, at the very least, interested in this idea. Guidance? Could you just make a new nut? One that extends beyond the end of the jaws and with a hole to match the diameter of the tap's shank?

Different tap sizes have different shank diameters, you say. So have a set of screw-in inserts for that longer nut that do match the tap diameters. A design that incorporates an O-ring in a groove could, perhaps eliminate the threads on the inserts, making the installation of the inserts just a friction event. Push in - pull out.

One thing that should be thought out is the question of slipping vs. tap breakage. I think that a modified, Tee handle tap wrench, as is being discussed here, could be mounted in a collet or Jacob's chuck with a controlled amount of torque to allow for some slippage. This could be more precisely controlled if one had some values of torque that different sizes of taps could endure. Anybody know of a table of such values? Would the tap manufacturers even have such data? Do they test them to destruction?

I feel a project coming on.

Paul, after a lot of thinking and playing with T-handles I feel that you may be right. I have one T-handle (made in India) that I am willing to sacrifice. It can hold from 1/4" to 1/2" taps. The holding is not precise and the tap can still move a little radially even when clamped. When not clamped tightly, the tap can move more. This is what we want, right? The tap needs to self align itself with the bore, it just needs a little guidance.

The T-handle shank is 21 mm in diameter, so I would need to turn it down a little so it would fit my 20 mm drill chuck on the lathe. I am almost positive this chuck would be able to hold the handle for 1/2" tapping. Even with 1/2" tapping limit I would have to be careful with the sliding tailstock. The tailstock for my 12" lathe is not very heavy and tapping force may be able to lift it.

[IkeHarris]

When tapping 6-32 in 304 you need some feel. You can't be dragging a tailstock along with you and expect a good outcome. This is how I do it. There is a good press fit to the t-handle and the other piece is snugged in the chuck. Look at McMaster-Carr 2550A64 also.

[Bented]

Cheap and simple MT tap holders in the tailstock.

There are other methods when rigid tapping.

[gellfex]

When tapping 6-32 in 304 you need some feel. You can't be dragging a tailstock along with you and expect a good outcome.

For me at that size, I don't power it, I untension the belt and turn the chuck by hand to get a good feel, and get frequent backoffs. My Logan 200 tailstock slides easily. But that would typically be through only 3/16 of material for a set screw to hold a perpendicular rod, it's not like I'm tapping 3/4" deep that way. I'd power AL or Delrin.

[psomero]

Regarding taps...

If a hand tap costs $5
and a spiral tap costs $15
I would pay the money
and buy the spiral tap.
My life is too short than to
put up with the dicking around
associated with hand taps.
Hand taps are for chumps.
If that offends you, tough titties.

-D

Buy two stub length tap drills while you're at it. No time to dick around.

[ammcoman2]

I have been very happy with the Tap Chuck I bought a few years ago for threads 1/4" and above.



I added the ratchet wrench which fits on a hex section added to the straight arbor (pinned IIRC). The MT2 blank was drilled and reamed for a sliding fit. This is used on the lathe

[Bob La Londe]

Can you elaborate? I have some spiral point taps (not spiral flute). Why would they perform better?

Heck, for common stuff I use spiral point taps for hand tapping if I have one. I think they tap easier than any other tap.

[mikey553]

I have been very happy with the Tap Chuck I bought a few years ago for threads 1/4" and above.

I added the ratchet wrench which fits on a hex section added to the straight arbor (pinned IIRC). The MT2 blank was drilled and reamed for a sliding fit. This is used on the lathe

So can you tell us how this Tap Chuck works?

[J Tiers]

Heck, for common stuff I use spiral point taps for hand tapping if I have one. I think they tap easier than any other tap.

Yep.

The only issue is that you don't do as well in blind holes. Standard taps work better for that. Spiral taps don't seem to get along with me very well, although they should be better for blind holes.

[Black Forest]

If you watch this video to the end it will show you how I hold taps on my lathe. The small chuck I bought off Ebay.

https://www.youtube.com/watch?v=ZcH3pdsrBmc

[ammcoman2]

[QUOTE=mikey553;n2049600]

So can you tell us how this Tap Chuck works?

[/QUOTE

https://www.rdgtools.co.uk/acatalog/VTA18-3.jpg . The part that grips the square section of the tap floats in the body as it tightens. The jaws are much like a regular chuck so the taps are centered. The idea of using the ratchet wrench is not mine - saw it at a Model Engineering show many years ago.

Geoff