Tailstock DIeholder

I mostly produce external threads by screwcutting, or with Coventry dieheads. On the odd occasion I use a die in the lathe I've been pinching a hand diestock between the work and tailstock barrel and hoping for the best.

I've been asked to quote for a small job that includes a M10x1 external thread. That's not practical to screwcut with my current lathe setup and for a 2 off it's not worth investing in a set of Coventry dies.

The above is a long winded way of saying I'm looking at acquiring a tailstock dieholder set. This is not an item I will use very often, so I need it to be functional but not necessarily sooper-dooper industrial quality. The offering from ArcEuroTrade looks attractive. Does anyone have one and can offer a view on it? Or suggest other suppliers to avoid?

Andrew

I've got one, from ARC I think. It works fine, not often used. For your job I would just use a hand diestock.

I’ve got one and was quite surprised at the quality given the low price I paid for it. I bought it at one of the model engineering shows maybe five or six years ago. Probably from Chronos, or Arc Euro when they still attended the ME shows.

Mine looks like: “2 Morse Taper Quad Head Tailstock Die Holder (Ref: TSD2MT)” on this page:

**LINK**

I have the same one, useful to get imperial as 25mm dies will fit in a 1" holder but not the other way around. Then again easy to make more holders. In the absence of a test bar I used it to align the tailstock.

Brian

The solution all depends on the length of the finished thread. For a 15mm length of thread the pinched by tailstock method would probably be acceptable but if it is for a 150mm long thread it may produce a bit of a drunkard's walk. Small errors at the start can be amplified as the thread is cut. If possible leave an extra bit of length on the end to be threaded and turn its diameter down so that the die just goes over it, this will give a good start to the thread. Then cut off the lead in section.

I do have a tail stock die holder but it fits into a tapping head to give controlled torque and minimal axial force to the die. It is also a lot quicker to cut a thread like this than single point cutting however for precision in pitch over the whole length of a thread the single point method is the best (if your lead screw is not worn).

Martin C

Thanks for the replies. It seems that the Arc one will do the job. The question is do I really need it? From memory the thread is only about 10mm long, or rather that's the length to a shoulder. No information given about how long the thread actually needs to be. Although it's nice to buy a new toy, albeit not an essential one, I've only got two to make so I may well use the pinched tailstock method.

I will be adding some design time to the quote. I've already had to point out that machining a slot with sharp internal corners requires a zero diameter cutter. And the M10x1 thread was originally specified as 3/8" BSP, which would have been tricky on a part made from 1/2" AF hex stock!

Andrew

If you do buy one and are threading upto a shoulder then take off the handle and remove the pin, that way you can just hold it with your hand and offer it upto a slow turning part then when you get to the shoulder your hand acts as a clutch, better than turning the chuck by hand. I use mine that way all the time unless it's a coarse thread which takes a bit more holding onto.

Would not take long to turn a spigot onto a bit of bar and hollow out the other side so you could hold in a tailstock drill chuck with the tailstock left loose.

I wonder is 1/8" BSP would suit them better as that is approx 3/8" diameter and may have been what they were thinking off, really depends on the final use whether BSP or M10x1 is likely to be a better choice.

J

PS I thought you had a slotting head for square corners

Andrew,

In that case don't bother with the dieholder.

Assuming your tailstock has an MT2 socket (or larger) remove your tailstock chuck and push your normal dieholder against the workpiece using the tailstock handwheel. OK you have to juggle a bit to do it, but the front of the tailstock barrel makes sure your die goes on square and stays square as you turn the die.

Regards Tom

There is another solution that may be possible, drill and tap the part and loctite a stud into it.

Martin C

I have one.

The handle is essential if threading M12, but I recommend turning the lathe manually

Works well.

Still need the die holder to make the stud as it's not easy to come by M10 x 1 studding.

Jason: I do have a slotting head on the back of the Bridgeport, but the recess is only 0.7mm deep on an existing part, so not practical. The designer has now changed the slot end to a semicircle of radius 10.25mm. Doooh, I was planning on machining the slot manually, not having to faff about with CNC for a 1 off

Tom: That's exactly what I've been doing

Martin: I could insert a stud, but the next diameter up is only 11mm, and there's a 6.5mm thru hole as well

Neil: Thanks for the heads up; I'll certainly put the Arc unit at the top of my list as and when I decide to buy

I've now been asked to quote for another part in 303 stainless with an external surface finish of 0.4µm, presumably Ra. That'll mean firing up the cylindrical grinder.

Andrew

With a button die, use the Jacobs chuck with the jaws retracted as backup, rest the die, not the holder against the chuck. For a flat in the tail stock I use a valve lifter from a Continental O-300, this has a body 5/8" dia x 1 1/2" long, with a 1" head on it with a nice polished hard flat surface, this is good for starting dies square.

Ian S C

What no 13/32" cutter?

A bit non standard but they can be had, depends what works out best for you time setting up CNC or just buy a cutter like this

Probably, but the radius is 10.25mm, so the diameter is 20.5mm. I definitely have a 13/16" endmill, but that's 20.64mm and the tolerance on the slot width is 0.05mm, so no go.

Andrew

My gripe is trying to find split button dies, what you get these days are not much more than die nuts without the hexagon. I do have some with an adjusting screw to set the size, very handy when making a number of threaded parts all the same fit.

Ian S C

These days many dies are of a level of quality that a split isn't needed.

My unsplit metric dies are the only ones I have that give their tolerance grade (H6, I think)

Easy to split a die if needed- 1mm cutter in angle grinder.

Postscript: I bought the Arc tailstock dieholder along with metric and imperial holders. Ordered it one day, got it the next. In summary it does what it says on the tin. A few more detailed points:

The units are nicely finished in a black oxide

The Morse taper (MT 3 in my case) is a good fit in my tailstock

The sliding parts, despite being ground, are a bit of a sloppy fit, probably a thou or two clearance. Not that it really matters, but one ought to be able to do better when grinding

Annoyingly the die holders are not marked with size, so it's easy to get confused between similar metric and imperial sizes

As expected the SHCS are a bit cheesy albeit better than some I've seen, I might replace them in due course

The biggest irritation is that the grub screws that hold the die are almost all blunt end. So the one intended to adjust the die doesn't actually enter the split in the die, dooooh!

Overall I'd say the unit is good value for money and is perfectly useable. Realistically it's not something I'm going to be using a lot, so I wouldn't have wanted to pay a premium from an industrial supplier, for probably a very similar unit.

Andrew

The VFD on the BH600G has a Jog function, and it works a treat in either direction.

Out of Hospital and waiting for biopsy result. 🙏

Geoff - Takes me nearly a week now to get over a general anaesthetic.