Tapping under power in lathe and mag drill

[Bill PhinnParticipant @billphinn90025]

My question is about arrangements for tapping under power in two different circumstances.

Firstly, I’d welcome recommendations on how to hold taps in the tailstock (other than in a Jacobs chuck) for tapping under power, ideally with the ability to “float” the tap so as to control its entry in to the work by hand if desired. I already use floating tailstock die holders.

Secondly, does anyone have any experience of this kind of tap holder? I was wondering how well this type would work in a mag drill. Would it be better or worse than an ER collet chuck? If neither is ideal, what would be?

[noel shelleyParticipant @noelshelley55608]

My mag drill takes a while to stop so I think it would be difficult to control. Noel

[HuubParticipant @huub]

I have made a floating tap (and die) holder for my lathe and it works very well. My lathes have no gearing on the spindle so torque is limited at low RPM. Depending on the material, I can get to M10 max. When the spindle stalls, I put the key in the chuck and finish the threads by hand.

For short small size threads, I use the CNC for rigid tapping. As soon as a threading tool fits the bore (M8) I use the CNC and a threading tool for making threads.

 

[DiogenesParticipant @diogenes]

Can you make an attachment for your die-holder for the taps – like a sidelock holder, with a body bored to suit the spigot of the static part of your die-holder.

The tap chucks look interesting, haven’t ever tapped with a mag-drill, as Noel hints, might be a bit of a clunky process.

A decent cordless pistol drill makes quick work of tapping away from the machines.

[Bill Phinn]

On 29 March 2024 at 21:25 Bill Phinn Said:

Would it be better or worse than an ER collet chuck?

What sort of collet would you use in the ER chuck?

It is possible to buy dedicated ER tapping collets, that have a square formed in the end of them to take ISO tap shanks.

If the manufacturers offer these for an industrial/production environment, it suggests that they do not consider a standard ER collet as suitable for use in power tapping.

The eBay ones will also be sized to suit ISO tap shanks. Comparing ER to eBay, you would need an eBay one for each size of tap you wanted to hold (say £11 each to cover M6-M16).

Taking Cutwel’s ER tapping collets as a baseline, to achieve the same range in ER, I think you would need ER32 size, five pieces at roughly £26 each plus the chuck if you did not already have it.

If you want to use a non-ISO tap, the eBay one is unlikely to work. You would need to research the ER option to see if the size of the square can be varied and the relationship between square a/f and shank diameter.

[JasonBModerator @jasonb]

What you need, Fits the die holders spigot and is free to slide and rotate. No need to wory about what happens at the end of the cut and being able to stop quickly. Just let go of the body and it will stop cutting. Subject to what size holes you are wanting to tap and your grip. Best with spiral flute or spiral point taps which clear the swarf from the hole.

The dedicated tapping ER collets with teh square hole are for rigid tapping on CNC machines where you don’t want to risk the tap slipping and going out of sync. With lack of control of stopping a lathe or mag drill something that will slip is an advantage should you bottom out or go too deep and hit the shank.

 

[FulmenParticipant @fulmen]

I recently made this style die holder: https://www.hemingwaykits.com/tailstock-die-holder (plus a suitable tap holder that fit like a die). Very happy with it.

[Howard LewisParticipant @howardlewis46836]

I bought a Tailstock Sliding Die Holder (Soba) and made a Sliding Tap Holder, to slide on the same arbor.

Deliberately a loose fit.

In this way the Tap can self centre in the hole, as can the Die over the workpiece, to minimise risk of broken Taps or drunken threads.

My Tap holder uses my ER25 collets, but is not clamped up too tightly.  In this way, the tap can slip, rather than break.

For a couple of newbies, to get them going, I have done similar things, but used a drill chuck to hold the taps. In this way, a variety of Tap sizes can be held

(My bench Tapping fixture, made from a redundant bench pillar drill stand,  uses a small drill chuck to hold the tap).

If the Tap slips, having become well engaged,  the rest of the tapping can be done by hand, where possible supprting the end of the tap, (Tailstock centre or a “Taptru” spring loaded support) to minimise the risk of bending and breaking the Tap. In this way the “feel” should allow the tap to be backed out, before it jams and breaks.

Howard

[bernard towersParticipant @bernardtowers37738]

As in your first post Bill I have a couple of those and have stripped one to make a couple more and they do what is says on the tin. I have just recently made one for small taps which is gripped by hand and let slip at will, not near the workshop at the moment but will post photo later. Of course there is the option of a Vertex type tap chuck!

[bernard towersParticipant @bernardtowers37738]

For very small taps you can always use eclipse pin chucks as they have 4 jaws, if you put a piece of rod in the tailstock chuck that fits inside the pin chuck this will keep it in alignment then you grip on the chuck makes it do the threading. Pictures of the recent one for taps up to 1/4″

[Anonymous]

I’ve never thought of tapping with mag drill; as stated I suspect it would be less than satisfactory. When I drill the holes to mount my cylinder on the boiler I will use the mag drill to drill the holes, but tap by hand.

I don’t power tap in the centre lathe, I just start by hand with the tap in a drill chuck and finish by hand if required. On the repetition lathe I always tap under power, mostly with spiral flute taps. The tap is rigidly held in a collar that then fits into a holder with a dog clutch:

When the holder reaches a set axial limit the tap stops rotating. Reversing the lathe engages the dog clutch in reverse, so the tap reverses out. Works very well and is fast, a few seconds at 500rpm.

Andrew

[Bill PhinnParticipant @billphinn90025]

Many thanks to everyone for the substantial body of replies.

Based on people’s suggestions (and dealing with the lathe first), making inserts for my existing tailstock die holders seems a logical solution. I’m not really sure how Jason has arrived at his solution though. Have you made a completely new bored-out body (the black part), Jason, to go over the straight shaft/spigot of the morse taper die holder mount? And what is holding the taps – a cut down chuck-type tap wrench? If so, what did you have to do to unite it with the black sleeve? I did watch your video with interest many months ago and never got round to asking you these questions at the time.

Bernard’s and Andrew’s lathe tapping solutions are impressive. Bernard’s looks doable, though would only be good for small taps as he says: Andrew’s looks like a work of thaumaturgy, and beyond my own powers to make it. Perhaps if I understood more precisely how it is made and works though it might be a less daunting prospect.

DC31K, I’m glad you raised the points about the ebay holders probably only fitting ISO taps; I was wondering about their fit. As for ER collets, I did know of the existence of specific ER tapping collets, but wondered, for reasons mentioned by Jason, whether it would be advisable to resort to this no doubt very effective but more uncompromising solution on my mill or mag drill. For the small amount of power tapping I’ve done on my milling machine (still out of action at present) I just used standard ER collets. They seemed to hold successfully when tapping steel as well as brass, but then the maximum I’ve power-tapped on the mill has been M8. The taps used were of course either spiral point or spiral flute into through-holes.

Coming to the mag drill specifically, mine is an MT2 taper 12 speed affair (slowest speed 100 rpm) with a reversible spindle. One of its marketing points is its tapping capabilities. I’ve tapped holes only up to M10 on it so far. At 100 rpm there is plenty of time to react and stop the spindle before putting it in reverse. Because there is no quill spring the tap feeds itself out in reverse and you don’t even have to hold the capstan handle at the end to stop the sudden upsurge you can get on a mill or bench drill.

I currently hold the tap in the mag drill’s supplied Jacobs chuck, which kind of works but very frequently lets the tap slip unless you tighten the jaws insanely (for me at any rate) firmly. I don’t own an MT2 ER Collet chuck (only straight shank and R8). I’ll probably buy one to see whether this is a better solution for holding taps in the mag drill using standard ER collets. I might also buy one of the ebay holders, which Bernard suggests perform OK.

The other possibility I’ve considered for mag drill use to avoid tap slippage is hex shank taps, which seem to be commonly and cheaply available in the smaller sizes at any rate, but this brings us back to whether I really want that degree of security against tap slippage if it carries with it a corresponding risk of tap breakage.

Bernard, is this what you mean by the Vertex tapping chuck? Or this one? How do they hold the tap exactly?

 

 

[JasonBModerator @jasonb]

A nice man from ARC sent it to me for my opinion, I said it was no good and he said I did not want it back. Actually it is nicely made but there were a couple of points that made us decide it was best not to stock it, I have since seen them available elsewhere.

It is the same body as the die holders fit into but they all have quite a small diameter spigot. The chucks are like those you find on the tee handle wrenches with two jaws that have the Vee in them. I expect one of these chucks could be cut down and silver soldered onto a suitable disc to fit an existing tailstock die holder.

I don’t really use it much but its quick if you have a small batch of nuts or similar to make.

 

[bernard towersParticipant @bernardtowers37738]

Bill its the first one they hold the tap similar to a tapping head which has 3 jaws at the front to keep the tap central and two jaws at the rear for driving the square.

[Author]

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