270 forum posts
I want to give power tapping a few metric on my ML7 a go whereby a machine tap is held in the tailstock.
To do so will require the tap to be held in a tailstock collet. I already own the Myford patent collets (those using a 1 1/8" Whit closing ring). Annoyingly I can't see these workign on the taslktock becuase any required adaper would constrict the 2MT bore.
So if I need to source another collet design,simplcity and cost, woudl plain 2MT collets suffice:
If so can I use M10 studding with a washer and nut at far end of tailstock barrel for the drawbar?
|Craig Brown 2||23/10/2021 03:54:08|
|49 forum posts|
Power tapping on the lathe doesn't require collets to hold the taps. I use a drill chuck to hold the taps, snug it down nice and tight and it will hold the tap no problem. The added benefit of using a drill chuck is that if your tapping a blind hole or the tap binds up for whatever reason then the tap should spin in the chuck rather than snap which would be the likely outcome if held in a collet. A keyed chuck is preferred over a keyless as there can be some issues backing the tap out in reverse because the chuck can undo its self, may not be an issue on a myford with a screw spindle nose as running in reverse is best avoided.
Sorry to deviate from the original question I just wanted to offer another option incase you were unaware.
Hope that helps
21613 forum posts
As Craig says a drill chuck will do or if you have an MT2 shank ER collet chuck that could be used in it's place.
Do be aware that things move fast once the tap engages particularly as the pitch increases so be ready to stop the spindle. I have seen some people that keep their hand on the keyless drill chuck and just loosen that rather than try and stop the spindle dead. But turning the spindle by hand is less stressful on the user.
You can also use a hand taper tap under power provided the hole is not too deep.
M10 studding easy to buy or thread some 10mm rod, not sure of Myford tailstock arrangement as to whether it will take a drawbar or not.
If you have a tailstock die holder then a tap holder can be made for that which may be the better option, with the tommy bar removed just grip the body and bring the tap upto the work, when you get to depth release your grip and it will just rotate allowing you to stop the spindle at your leisure
Also be careful when powering the tap back out as you have a screw on chuck.
Edited By JasonB on 23/10/2021 07:29:12
|586 forum posts|
Particularly with regard to the Morse taper collets (with limited grip range), have you confirmed the shanks of the taps you want to use fit a standard collet diameter?
The ER collets might work better as they have a range of gripping diameters.
|Tony Pratt 1||23/10/2021 11:01:28|
|1752 forum posts|
I do have a tail stock tapping chuck bought in a fit of enthusiasm, used it once but now just use a drill chuck.
|Martin Connelly||23/10/2021 13:11:13|
1929 forum posts
I've got these two MT2 tapping chucks that have adjustable slip and are sprung both in and out of the body. It makes power tapping in the lathe easy up to M12, I've not tried anything bigger. I have some spiral machine taps for the bigger sizes and the swarf just comes out like you were drilling a hole. I put a split collar on one to stop the taper slipping in the tail stock when used for bigger sizes. I didn't buy these as new so I don't think I would be able to justify the cost for them if that was the only way to get them. I don't have a full set of collets but do have some Snap-On tap driver sockets that are easily modified to fit, they just require skimming to a slightly smaller diameter and a slot for the drive pin. the basic principles are quite straightforward and I think a home brew design could be made.
270 forum posts
Thanks chaps, appreciate all the advice.
I should have said that it was actually Cutwel technical advisor who recommended this. So in the spirit of sharing knowledge, they advised: (who themselves do lots of proper engineering themselves),
For a Myford size, power tapping with tail stock collet is the smart choice esp can maximise squareness and rigidity. Furthermore the motion of hand tapping actually slightly degrades the thread form due to the repeated forward and backward necessary to clear chips. Cause a slightly looser fit. Plus get the powder metal HSS which are more shock absorbant by their nature.
(Must say was refreshing change to have a long friendly chat with experts. On phone for about 30 min!)
Edited By choochoo_baloo on 23/10/2021 14:24:02
7675 forum posts
Could some kind person explain how power tapping is done in the lathe when the tap is held firm in the tailstock, whether in a collet or a drill chuck?
On the lathe I tap by hand with a T-wrench kept straight by a spring-loaded plunger held in a drill-chuck. As the tap goes in, the plunger extends, allowing movement where needed. It's also possible to eject chips by going backwards.
When power-tapping, is the tailstock left loose so it's pulled along as the tap goes in, or does the operator drill in by spinning the wheel? Also, how are the chips dealt with? Does the method require spiral taps rather than ordinary ones? I'm having difficulty visualising how it works without breakages!
Although it feels like I've owned a lathe forever, I've never tried power tapping with one. Blast it, I'm still a beginner!
|Nigel McBurney 1||23/10/2021 15:46:52|
944 forum posts
I have always used a Jacobs chuck to hold taps in the myford s7 its ok with small taps but larger taps are more difficult to stop spinning in the chuck ,not having reverse I release the jacobs chuck and then reverse out the tap with a tap wrench.Er collet chucks,have a really positive grip so can cause tap breakages or worse still spin the morse taper shank in the tailstock barrel and damage the internal morse taper,after the s7 is a cente lathe and the taper in the tailstock must be kept in good condition. To get over the risk of damaging the taper or the keyway in the tailstock,it is reaonably easy to make an attachement for holding taper shanked tooling on the cross slide,any strain then goes onto the saddle,drills can also be power fed,taper sockets can be obtained which have ground parallel outside diameter,its the just acase of mounting this in a suitable block and boling ut to the cross slide. For my Colchester Master I have a cross slide mounted 4 mt sleeve so with a ER 40 collet holder I have tapped up to 1.125 whit with no tap slip in mild steel and the reversing motor clutch allows reversing the tap out easily,and no strain on the tail stock,plus I can drill under power feed up to 2inch dia. Small tap holders with a slipping friction clutch like the Archer are ok but take time to set the clutch and while setting there is the risk of tape breakage,ok if there are say 200 holes to tap. I have an Archer tap holder,brand new a gift from a friend but as soon as I had ER collets its never been used since.
21613 forum posts
Dave, you don't clamp the tailstock to the bed so the tap pulls it along. You then either need to stop the spindle at the right time or loosen the keyless chuck. I tend to just turn the chuck by hand while gently pushing the tailstock towards the work, might be different if I had a batch to do but mostly it's just one or two.
21613 forum posts
As I mentioned earlier a tailstock tap holder that fits into a die holder means a lot less bum clenching when it comes to stopping the spindle as the grip of your hand acts like a clutch so things will slip rather than snap a tap like they would if it were held very securely. This one holds the square end of the tap much like the "T" type tap wrenches do. M6 into 6082 Aluminium with one of Uncle Ketan's spiral flute taps
Edited By JasonB on 23/10/2021 16:15:54
Edited By JasonB on 23/10/2021 16:20:13
|Howard Lewis||23/10/2021 17:52:55|
|5528 forum posts|
I tap under power (Admittedly using the "Jog" function of the VFD contyrol box )
A Mandrel Handle comes into it's own on lathes lacking this facility, and allows the operator to be aware of the torque being applied, before the Tap breaks!.
Having used a Tailstock Sliding Die holder, I made up an ER25 collet holder for taps of various sizes.
A ME 40 tpi thread will not withstand trying to pull a heavy Tailstock along the be when the Tap is held in a drill chuck.A sliding Tap holder imposes minimal load on the Tap to move it forward into the work.
Torque reaction is taken by a stud screwed into the body, which rests against the side of the front toolpost.
It has the advantage, that if anything jams, the Tap ,slips in the collet rather than breaking. If it is just things getting tight, the Tap can be left in the work, the tap holder removed and with the Tap, hopefully now correctly aligned, the job can be finished using an ordinary Tap Wrench.
|Martin Connelly||23/10/2021 17:58:52|
1929 forum posts
|bernard towers||24/10/2021 23:00:22|
|336 forum posts|
No 2 morsetaper tap holders are available on our favourite auction site, Ibought 1 and stripped it and made a few for common taps but also use a tapping chuck and most of my tapping is done under power usually fast backgear and using the VFD preset reverse and as the point is reached press he green button and lathe is reversed ejecting the tap.
7675 forum posts
Thanks Jason, I shall give it a try. Still concerned about what happens to the swarf though.
Ages since I last snapped a tap, perhaps today!
21613 forum posts
That is what machine taps are made for they push the swarf ahead of them or direct it out behind.
As I said you can use a hand tap if the hole is not too deep, say if threading a nut but you could get a build up of swarf in a deeper hole particularly with small threads.
M12 Hand tap under power in the SX2.7, tap won't know if it's in a mill or lathe.
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