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

[J Tiers]

I believe that here are talking about a simple design for a torque limiting/limited threading device that could be made by an average home shop machinist for his/her own use. I don't think that a "torque meter" even applies to this discussion. The "torque meter" is the operators feel.

Of course it applies.... "feel" is fine, even if there are no numbers, and it is a bit unrepeatable. But you have to be "feeling" something that actually involves the torque, and not some unrelated thing like the tailstock wheel.

That Hemingway thing is just a clutch. You are supposed to feel the lever in one direction, while needing to hold it in position in another direction, so as to apply just the right torque. Connecting the two with a loose lever is not the best plan.

Can that be done? Sure. Can you do it perfectly 100 times in a row? For a 4-40 or 2mm tap? Well, that's a different thing.

And no, that is not similar to power steering.

"Torque limiting" would mean a setting, i.e. a "meter" that measures torque and releases at a given torque.

A "torque meter"? Sounds like a torque wrench and there are several designs.....................................

Ummmmmm....... NO !

A device to MEASURE the applied torque, NOT a device to APPLY a given torque. But no matter, it's not a good idea compared to other possibilities, as mentioned.

[npalen]

Tapping torque and breaking torque:

https://parlec.com/Parlec/media/technical_specs/Tapping-Speeds-Torque-Requirements.pdf?ext=.pdf

[npalen]

Some more.

http://tapmatic.com/tapping_questions_torque_setting_data_for_hss.ydev

https://www.kennametal.com/us/en/resources/engineering-calculators/holemaking-calculators/tapping-torque-and-horsepower.html

[Paul Alciatore]

Thanks for those tables. I did not know they existed. They will definitely be helpful.

Some more.

http://tapmatic.com/tapping_questions_torque_setting_data_for_hss.ydev

https://www.kennametal.com/us/en/res...orsepower.html

[Doozer]

Morse taper, tap collets may exist and may be available on E-bay, but I really doubt that the two sets you link to are such.

The collets in the two sets in your links are nothing more than simple, common fractional inch collets which are PLAINLY labeled as such in the photos. The first set, in order of size, contains:

1/8", 3/16", 1/4", 5/16", 3/8", 7/16", and 1/2". Those are NOT diameters of taps.

And the second set:

1/8", 5/32", 3/16", 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", and 3/4". Again, those are NOT diameters of taps.

I got these numbers straight from the collets themselves or the boxes, in the E-bay photos. Contrary to what someone said, the seller does have an accurate description. What the seller seems to have trouble with is putting them in any order by size. Or perhaps he/she is just too lazy to do so.

I strongly suggest that no one purchase these collets thinking they are made for taps. They aren't! They ARE just common, fractional sizes.

They are for automotive shank drill bits.
Not taps.
I've got a bunch.
Get yourself a Scully-Jones tool catalogue.
Get smart.

-Doozer

[J Tiers]

I have some of those drill collets that came in a toolbox. They have a socket at the bottom for a drill, that has two flats on it. No, they will NOT fit any tap that I know of, the recess is not square.

Yes I tried them, because why not.... No other use for them, I have maybe three drill bits of that type, and the drills work fine in a chuck.

Yes, there ARE "tap drivers". They look pretty much like the drill collets, but are for taps. Sizes may overlap as well, in fact the sizes that Doozer says are no good are standard sizes for tap drivers.

https://www.mcmaster.com/products/tap-drivers/tap-holders-for-drill-presses-and-milling-machines-6/

[Paul Alciatore]

J,

I have two, no three torque wrenches that MEASURE the torque that is being applied. I purchased two of them specifically because they had that property. I wanted to measure the torque being applied to, of all things, taps. Here's two of them. I can not find the third, smaller one at the present time but, IIRC it is similar to the longer one, just smaller.


As I said above, there are different types of torque wrenches. Even digital ones.

https://www.mcmaster.com/products/torque-wrenches/

Just as one possibility, I can imagine the pointer on one of the types shown being used to trip a clutch release when an excessive torque value is reached. Or the electronic type could keep track of the torque value in software and release a magnetic clutch. There are many possibilities. I can't believe you didn't see at least some of them.

...<snip>...

"Torque limiting" would mean a setting, i.e. a "meter" that measures torque and releases at a given torque.



Ummmmmm....... NO !

A device to MEASURE the applied torque, NOT a device to APPLY a given torque. But no matter, it's not a good idea compared to other possibilities, as mentioned.

[Paul Alciatore]

I was talking about the E-Bay collets, not anything in the Scully-Jones catalog. The ads are down. The items sold. But there was nothing in the descriptions or photos on E-Bay to indicate they were anything except plain, ordinary, fractional sized, round hole collets. Absolutely no reference to holding taps or "automotive shanks". And the price was dirt cheap. One set, IIRC was $37 for around 8 collets. McMaster's prices on MT tap holders run $40, $53, and $80 each for MT2, MT3, and MT4 sizes respectively. And McMaster's web page plainly states that they hold taps. The photos in McMaster show the side openings needed to machine the flats that grip the squares on the taps. The collets on E-Bay did not have those openings so machining such flats would have been awful difficult.

I think we are talking about two different ball games, in two different ball parks, in two different cities, in two different countries. And probably on two different PLANETS!

I don't have even a single one (collet or automotive shank drill bit) and, at those prices, am not likely to ever have one. So what? But thanks for the education. Learning is why I am here.

They are for automotive shank drill bits.
Not taps.
I've got a bunch.
Get yourself a Scully-Jones tool catalogue.
Get smart.

-Doozer

[Doozer]

I am not sure it is a hard fast rule,
but generally I have noted the pattern
of 4 split collets like this have been tap collets
and the 2 split collets have been automotive shank drill collets.
Not sure of our personal planetary alignments, but whatever.

By the way, less than $70 for all those collets is a smoking deal
if you need them, but again, whatever.

[mikey553]

The function I like with the 3” 4 jaw scroll Chuck is it will hold virtually any size tap and does double duty holding threading dies with appropriate die receptacle,the Teflon coated spline section is a bargain at $15.

You have mentioned a spline section in your setup. Is it shown on this picture? May I ask where you got it from? I am thinking about doing something similar and this may save me some trouble.

[J Tiers]

J,

I have two, no three torque wrenches that MEASURE the torque that is being applied. I purchased two of them specifically because they had that property. I wanted to measure the torque being applied to, of all things, taps. Here's two of them. I can not find the third, smaller one at the present time but, IIRC it is similar to the longer one, just smaller.

................................................

Just as one possibility, I can imagine the pointer on one of the types shown being used to trip a clutch release when an excessive torque value is reached. Or the electronic type could keep track of the torque value in software and release a magnetic clutch. There are many possibilities. I can't believe you didn't see at least some of them.

Torque wrenches are pretty irrelevant. You are not going to drive a tap with a torque wrench, most likely, although one could do that. They are just not conveniently shaped and sized for the task, and even the "releasing" type only "click" they do not stop driving the bolt.

The means that a torque wrench uses to determine torque is a measurement. Some, probably not all, of those means of measurement may have application to the tap driving problem.

I find it hard to believe that you would not have seen that the key element is not the measurement, but the automatic releasing. That's the issue. Watching a dial is fine, and one could do that. But you will miss a few over-torque cases, and break taps.

A good tap driver would not depend on attention to a measurement on a dial, do not depend on your reaction time after seeing the dial reach some number, etc. The Hemingway is the worst, since it doesn't even give a measurement, and the amount of movement necessary to go from slipping to locked tight is very small.

There are cases in which the Hemingway s adequate. But I do not think that power-driving 4-40, or 2mm taps are it's best feature. You want something that you can set and which releases reliably.

A version of the Hemingway which was not so abrupt, was somewhat limited in maximum torque, and which did not mix up the operating handle between feel and release would make the concept of "feel" far more practical. I think it is possible, maybe someone can make one.

Edit: The real key is gradual engagement, or other means to control the torque over a fairly wide range of control arm/dial/etc motion. That way you can adjust to suit different taps. Even a spring between the control and the forward engaging cones on the Hemingway would be a potential improvement.

But I do not think the Hemingway was ever intended for that purpose. It was not intended as a torque control, but as an "on/off" drive with capability for easily reversing out (you would not want to push inward to engage the clutch for unscrewing the tap).

The Hemingway device seems to be simply for quick disengagement and reversing, for use when tapping through holes, or holes where the exact depth of thread is not critical. Go until through the part, then release and engage again after reversing. For that it is fine.

[npalen]

Just some food for thought regarding this thread: A hydraulic quick disconnect has some features that might be applicable particularly for a floating feature to let the tap or die find its own center. There is about 0.006" of radial clearance on this particular one shown which lets it float while still held centered by the internal o-ring. The spring loaded balls in the receiver are released to free the plug when the outer sleeve is pulled back.

I have to wonder if a torque setting could be achieved with an o-ring of given size and durometer surrounding a series of balls fitting into pockets on the mating plug.

[npalen]

The Hemingway device seems to be simply for quick disengagement and reversing, for use when tapping through holes, or holes where the exact depth of thread is not critical. Go until through the part, then release and engage again after reversing. For that it is fine.

You really need to build and use one. You would be totally surprised.

[J Tiers]

The Hemingway device seems to be simply for quick disengagement and reversing, for use when tapping through holes, or holes where the exact depth of thread is not critical. Go until through the part, then release and engage again after reversing. For that it is fine.

You really need to build and use one. You would be totally surprised.

Not even one chance. Not making one. If I make anything for the purpose, I will design it, as I don't like the Hemingway design.

[Paul Alciatore]

J,

I was never suggesting that a torque wrench, any kind of torque wrench should be incorporated in a tap or die holder.

What I was and still am saying is that the mechanism used in SOME KINDS of torque wrenches DO MEASURE the torque. And that measurement could be used to control, mechanically or electronically or some other way, the action of the tap or die holder. This is what the expensive tapping heads already do. What we are looking for is a way to use this to control an inexpensive and relatively easy to construct HOME SHOP die holder.

If this were easy, the big guys or the makers of cheap, imported tools would have already done it. But should we allow that to stop us? Perhaps the brain trust here can come up with something. Perhaps it even will. And I think we all agree that SOME way of detecting the torque is necessary. Some say it is the operator. Others think it could be in the mechanism. But, if tap breakage is going to be avoided it is needed.