DIE HOLDER VS SINGLE CUT

[benmychree]

I just did a search to find my Geometric die brochure describing all the different types, but of course stuck out, but my advice would be, consider ONLY the style D die head.

This is the size I have. I have chasers from 4-40 up to 1/2-13. I just hold the straight shank in my tailstock Jacobs chuck, that opens to 3/4”. I can change to a different thread pitch in maybe a minute, after I remember afresh how to do it each time.
The thread quality for me is at least as good as single point, and I tell you, zap, it’s done. I would and have set this up to do a single part.

All true and good advice. I made a sleeve that fit my 9/16 die head that slipped over the tailstock quill, that had a key to engage the keyway in the quill and a setscrew to keep it from sliding off. I would set the carriage in position to limit tailstock travel for the length of threads wanted; the tailstock would run into the carriage and the die would trip and open up. Later I adopted the Aloris boring tool holder with 1 1/2" hole and mounted the die head in it and used the carriage stop to trip the die. I have tried using the lead screw to power the travel of the die head, but generally, this does not seem to work, as it seems that deviations in the pitch diameter (of the part being threaded) effect the lead of the screw being cut, and generally with a long cut, the die will pull itself off (trip) before the desired length is reached, so the lead of the thread would be longer than expected, this with undersize pitch diameters.

 

[benmychree]

I don't like the idea of holding tools other than centers in the taper of the tailstock quill for jobs such as heavy drilling, etc, this is how the tapers get buggered up, resulting in inaccuracy. One exception would be for tailstocks quills that incorporate a tang slot, such as on American Pacemaker lathes.

 

[Winegrower]

I have tried using the lead screw to power the travel of the die head, but generally, this does not seem to work,

Huh, never thought of that. That would imply a big mismatch between lathe tpi setting and chaser tpi, no?

One exception would be for tailstocks quills that incorporate a tang slot, such as on American Pacemaker lathes.

Agree, the Takisawa has a tailstock tang slot and all the MT3 accessories have a tang.

 

[benmychree]

In the above I stated that the die head would often pull off when attempting to use the lead screw to follow it up; If the lathe is set up for the same TPI pitch of the chasers, one would think that it should work, but on a die head, if the die is adjusted for a smaller pitch diameter than standard (or larger, for that matter) the die will cut a pitch that is slightly shorter or longer than if set to precise pitch diameter, even then long screws cannot be counted on to be an accurate pitch in their full length, this is why long screws are single point threaded in the lathe or thread milled, or finish ground.

 

[riversidedan]

AARON W ............you hit the nail on the head!


Personally I find using a tap or die easier than single point, but that is because to single point I usually have to use change gears or have to set up a threading accessory

 

[benmychree]

A tap will nearly always cut a good thread to size, you cannot say that for cheap button dies, bad finishes and drunken threads are all too common.
I have never had to thread on a non QC lathe, but I can sympathize on having to swap nasty dirty change gears. When I have to thread special pitches on my lathe, I have to go through the same mess, even though I do not lube them with anything but oil.

 

[Ultradog MN]

If you are doing production work where time is a big factor then using a die is probably the way to go. But imo, few turning jobs are as satisfying as single pointing a set of threads.
I cut quite a few threads while I was in the Navy 45 years ago. Didn't run a lathe but a few times since then. About 6 years ago a friend needed to make a new mandrel for a buzz saw for his tractor. 1 1/4x7 threads iirc. He had a new Grizzly 12x30? but didn't know anything about machining so he asked if I could still cut a set of threads. I said I think so and showed him how. It all came back to me as I went. I ground the tool, figured the depth to cut (.750/N) and cut them to fit a new nut he had. It took us half a Saturday to do it but time was not an issue.
They came out perfect and he was both pleased and amazed to watch it all happen.
I'm just getting back in to a bit of machining after a looong hiatus. Bought a lathe a couple of months ago and am looking forward to cutting some threads. So I say give it a try on some scrap. It is simple, enjoyable and satisfying to do.