Lathe threading disengagement set-up

[gatz]

Often times, there's a need to stop a threading operation at exactly the same place.
A dial indicator generally works, for the most part, but it's easy to make a mistake; usually with dire consequences.

I needed to thread some 4140 pieces right up next to a shoulder & with the least amount of under-cut.
Blank parts were turned to 3/4" diameter and had the necessary undercut in the 3-jaw chuck.

I set the lathe up with a Limit Switch, a 110v Solenoid Valve and a small Air Cylinder.

The adjustable carriage stop is set to trip the Limit Switch at the right carriage position, which then powers the Solenoid Valve which in turn sends air to the Air Cylinder.
The Air Cylinder pushes the threading lever out of engagement and the carriage stops abruptly.

It worked much better than I had anticipated. Sure saved alot of time & worry too.

I didn't take pictures of the Solenoid Valve or the Air Cylinder. They're just common items.

parts with threading complete;



a link to the operation;

https://drive.google.com/file/d/1FSa...ew?usp=sharing

[Frank S]

Meed pictures of the set up.the video just shows the limit sw
Anytime I ever had to thread right up to the flange I preferred to thread out instead or thread in.
to do this I ran the lathe in reverse with the cutter inverted. this way I could start right next to the flange the only relief or under cut as you called it was the depth of the cutter.

[volodar]

Can't run my circa 1900 16x40 or so Hendey in reverse, as the chuck unscrews!

[Frank S]

I can understand that, A couple of my La Blonds have threaded spindles, but they are a tapered thread nearly impossible to to remove the chuck from the 1917 16 inch with 2 " through bore
the 1951 19 by 60 has a short nose adapter installed. with the 3 jaw the bolt pattern just scrapes the spindle threads and will not unscrew but the 4 jaw uses the larger bolting pattern and it will allow the nose adapter to unscrew. Someday I would like to convert both of them to a d 1-6 and the 26 inch to a D1-8 but the 26 inch has the long nose which uses a spanner nut to hold the chucks in place do it is not bad the only thing I really dislike about the 26 is the 1.5 inch bore

[PJs]

A bit confused here as the video show a Jet faceplate on the headstock? Do you have 2 lathes?

PJ

[Toolmaker51]

Lathe threading disengagement set-up...

The adjustable carriage stop is set to trip the Limit Switch at the right carriage position, which then powers the Solenoid Valve which in turn sends air to the Air Cylinder. The Air Cylinder pushes the threading lever out of engagement and the carriage stops abruptly.

This apparently works effectively. Pneumatics; good solution for what would be a tricky action through mechanical retrofit. Your adaptation's made to order for recent tool retraction devices posted lately.
I think we'd all like to see the linkage in operation, hint - hint. I'm interested where adjustments are, if any, past the bed stop. I'd want zero free play, probably via Heim joints.
No matter how enthralled I am with distinctive lathes, very few have threading kick out mechanisms. Not many even kick out carriage feed travel, and each I recall depend on a cam and finger.
I'm guessing worries on inertia of chucks, carriages and maintenance keep machine engineers from making them common.

[gatz]

A bit confused here as the video show a Jet faceplate on the headstock? Do you have 2 lathes?

PJ

? PJ....... there's no faceplate on the lathe

[NortonDommi]

Hello gatz,
Very effective. Like Frank S. I like to thread away from the chuck and also have 1/2" & 3/4" Coventry die heads but I like your setup.
Question? The tube over the leadscrew is that an add on? I have some thoughts as to what for but would like to know.
Cheers.

[gatz]

Believe me, I would have done that, but I'm using ThinBit threading insert & holder.



And I don't have an adjustable QC tool-holder

2 problems
1) Just flipping the tool over wouldn't work.....a Left-Hand holder would be needed and some way of changing the height (the Jet tool-post is fixed height)
2) It would work for threading OUT from the shoulder, but I'd have to make a mount for it on the opposite side with the right-hand ThinBit & holder flipped over.

That's the reasons for me doing it this way.

Here's a few pics of the mechanism. ...I had already taken the set-up down, so didn't make a video of that operation in its entirety; but remounted the components temporarily for those who asked to see it.

[gatz]

Hello gatz,
Very effective. Like Frank S. I like to thread away from the chuck and also have 1/2" & 3/4" Coventry die heads but I like your setup.
Question? The tube over the leadscrew is that an add on? I have some thoughts as to what for but would like to know.
Cheers.

The tube is what came on the Jet lathe. Its purpose seems to be to keep chips (esp long and stringy ones) out of the lead-screw, and ACME screw as close up to the headstock as possible.