Self extracting lathe tailstocks

A common drawback with smaller lathes is the length of the Morse taper if it has a tang. The tang was intended to be used for extraction with a wedge through a cross slot, but not all lathe tailstocks utilise this feature. Self extraction is common and both my 7 x 12 Chinese and the Atlas 12 x 24 at the museum have it and this limits the stroke of the quill by 1". Only an inch, but a handicap when the between centres is only 12" and even the Atlas only has 2" movement when it has 3" of graduations. The ansver is to shorten the MT by removing the tang and turning the end to allow just enough to break the taper. I have shortened both Chinese and genuine Jacobs MT's and drilled the ends. There will be some pictures when I get them added to my album.

Edited By old mart on 22/12/2022 17:00:39

What a good idea. Never thought of that.

Steve

Good idea, will rember if I get to that situation.

You can also get tangless arbors which saves paying for something you are going to cut off, also often drilled and tapped so you can make use of them in a drill or mill. If the tapped hole is too deep and prevents the tailstock ejecting the arbor then a short length of studding or threaded rod with a screwdriver slot sawn in the end will plug the hole. handy for those like me that have MT3 tailstock and a mill with matching taper.

The tangless arbor is the best of all worlds use with a drawbar, with a screwed in tang for the drill press, and a screwed in plug for self extractors. The first picture is of the 5/16" Kawasaki chuck used on my 7 X 12, the hole allows a greater length of MT while extracting about 1 1/2 turns before the leadscrew bottoms. The end for the Atlas is flat because the end of the leadscrew fills the small end of the MT socket. I already had the tanged arbors

A complaint we have had on here more than once is that having shortened the arbor to work on one lathe after a switch to a new lathe it not been able to eject the short version. In this case one solution is to fill the gap with a ball bearing or two. The advantage is that after removal of the arbor the ball runs out down the taper.

With tangless arbors, I have had just the reverse problem, and not been able to eject the arbor.

Having finally managed to extract the arbor, my solution has been either to screw in a tang (Got mine from Arc Euro ) or to fit and extension, (Screw in or press in ) so that the self eject feature then functions.

Howard

All the above is good stuff and the screw in option is what I use on my current minilathe but I don't really like self ejecting tailstocks.

When I used an ML7 regularly at a workshop years ago I kept a length of tufnol bar and a small hammer in my toolbox to release tapers.

When they upgraded the ML7 to the Super 7 I could never understand why they made the tailstock self ejecting - it decreased the bed length and allowed chucks and centres to come loose and flap about when drilling holes by advancing the tailstock body to get more depth - if the chuck was then withdrawn too much. As a teenaged learner a half inch Jacobs chuck rattling about was scary!

Cecil Moore was a member of my club at the time but I never thought to ask him why.

He might well have replied that the intention was to encourage users to get the lever feed accessory!

had always thought that self ejecting Tailstocks started on Industrial lathes.

Much kinder than using a hammer

Using the screw thread of the Tailstock allows a large force to be applied, gradually (Not as effective as a suddenly applied force, but less likely to cause damage / wear )

If you think about it, a screw thread provides an enormous mechanical advantage (Effort distance / Load distance ) Which is why you can jack up a fairly heavy car withh little effort, but a lot of handle turns.

Howard

If anyone is thinking of shortening their arbor to gain centre distance and quill stroke, here is the method I used. Hold the front of the chuck and use a centre to support the tang end. Using a carbide insert, turn the end down about 0.020", 0.5mm, having already decided exactly where the new end should be. Then you should be able to use a hacksaw to cut the end off, parting is not recommended as the work is not supported well enough. You may be able to face off the end if the lathe chuck gives enough support, otherwise grind, linish or file the end flat.