Live Center Chuck

[Mark Jundanian]

Is this a bad idea? If so, why? And how bad?

The photo is just a mock up of what I'm considering. The tailstock chuck is not attached in the photo, just pressed against the blank. If I do this for real there will be a chuck on a tenon at the headstock and a second chuck on a tenon at the tailstock. The tailstock will have a Robust live center and chuck adapter. The tail stock could be free to move on the ways, but I'm thinking it should be secured. RPM would probably be between 1200 and 2000.

The goal is to be able to repeatedly reverse the mounting while accurately maintaining alignment. There may be other solutions, but my primary interest is an evaluation of this one. So if it's a bad idea, why and how bad?

 

[Robert D Evans]

It'll work just fine. I've done something similar when making segmented vases. I turn the inside of the two halves and then glue them together and finish turning the outside using this method.

 

[hockenbery]

Should work as long as the trail stock is used.

what are you trying to do. There may be a less complicated solution.

 

[Mark Jundanian]

@hockenbery , my plan is not entirely hatched yet. At this point I'm trying to see how it might work and if it's aesthetic enough to give it a go.

Whether or not I go ahead with it I want to know if this top and bottom double chuck mount will work, even if just for future reference.

To answer your question directly, though, I want to start by turning a portion of the bottom, then flip the mounting and partially turn some of the top, then flip back and continue turning the bottom, then flip and complete the top, then finally move to a donut and remove the bottom tenon.

Maintaining alignment with all the flips is key and while I could dismount and remount the tenons this wouldn't be as reliable as dismounting and remounting a chuck on a spindle.

 

[Tom Gall]

@hockenbery , my plan is not entirely hatched yet. At this point I'm trying to see how it might work and if it's aesthetic enough to give it a go.

Whether or not I go ahead with it I want to know if this top and bottom double chuck mount will work, even if just for future reference.

To answer your question directly, though, I want to start by turning a portion of the bottom, then flip the mounting and partially turn some of the top, then flip back and continue turning the bottom, then flip and complete the top, then finally move to a donut and remove the bottom tenon.

Maintaining alignment with all the flips is key and while I could dismount and remount the tenons this wouldn't be as reliable as dismounting and remounting a chuck on a spindle.

This should work without any problems....on the exterior. Not sure what you plan to do, but if it's anything like the pieces you have been making I think the chuck may interfere with access to turning the interior. And, if any of the piece gets thin or the part mounted in the chuck gets too thin there is the possibility of breakage due to the weight of the chuck and/or torque of starting or stopping the lathe. Of course this can be mitigated somewhat by gradually turning the speed up or down before starting/stopping.....IF you remember! Again, I don't know what you want to do so this may not apply.

 

[Mark Jundanian]

I was off to try something different, but after some more drawing & designing I'm not convinced it would be all that "purdy", at least not for as hard as it would be to pull off.

Your point about tool access close to the tailstock is a good one. That's always a problem to solve. In this case I would probably had to rely on a swan neck, which is not my favorite.

 

[Gary Beasley]

If you have a Oneway live center you can get an adaptor that screws onto it that you can then screw your chuck onto. I use mine as an aid to centering bowls on my vacuum chuck.

 

[GRJensen]

I do something akin to this every time I turn a larger/taller segmented vessel. I don't see any potential for danger at all. I have a Live Tailstock Chuck Adapter that I use in conjunction with either 1" x 8tpi chucks or 1-1/4" x 8tpi faceplates.

 

[Bill Boehme]

Is this a bad idea? If so, why? And how bad?
View attachment 34930
The photo is just a mock up of what I'm considering. The tailstock chuck is not attached in the photo, just pressed against the blank. If I do this for real there will be a chuck on a tenon at the headstock and a second chuck on a tenon at the tailstock. The tailstock will have a Robust live center and chuck adapter. The tail stock could be free to move on the ways, but I'm thinking it should be secured. RPM would probably be between 1200 and 2000.

The goal is to be able to repeatedly reverse the mounting while accurately maintaining alignment. There may be other solutions, but my primary interest is an evaluation of this one. So if it's a bad idea, why and how bad?

I did that once for the same reason that you stated ... the need to frequently reverse the piece. However, I found that the idea wasn't quite as bright as I had originally envisioned. Some things to consider include:

• How good is the boresight alignment between the headstock spindle and the tailstock quill? No woodturning lathe is perfect and most are just good enough for typical turning needs. The Oneway live center bearings have some free play which is a good thing because it allows a bit of flex. Otherwise there could be some forces that might possibly weaken a tenon.
• If we were turning metal things would be much better behaved, but wood never ceases moving as material is removed and internal stresses are rebalancing. Even dry wood moves ... especially if it is something like the highly figured maple that I was turning.
• I think that the speed range you mention is too fast.
  
• My final solution was to switch to use my Vicmarc 120 chuck with both tenons sized to the perfect circle diameter of the jaws. This is the only diameter in which the dovetail jaws and tenon make full contact around the whole circumference and enables remounting the tenon in the chuck with repeatability as good as having chucks mounted on both sides. Note: Oneway also makes dovetail jaws, but I didn't have any at the time.

 

[Don Wattenhofer]

The one way live center that I have came with a variety of cones that screw onto the 3/4-10 thread on the cup center and the inserts on the one way chucks have a chamfer on the female thread that would center on the live center so the chuck would not need to be attached via an adapter.

 

[Robert D Evans]

I've use threaded glue blocks for a lot of things that have to be reversed. Make a glue block with a Bealle tap for the size of your spindle. You can put one on each side of the project and reverse it whenever needed with alignment assured. Just screw it onto the spindle and you can use a large cone in the live center for tailstock support. You can also reduce the glueblock as necessary as your project requires. And if you hit the glueblock while turning, it's no problem. If you make contact with a steel chuck while turning, you're going to have problems.

Sometimes old school has it's advantages.

 

[Mark Jundanian]

That's an interesting approach. I don't have the taps, but there are retailers ready and willing to remedy that deficiency.

I would imagine that the glue block would need to be hefty, maybe as big as the chuck, but as you say it's size can be reduced as the mass of the work piece is reduced. And the tailstock can be withdrawn as work progresses to the center of the work piece from the periphery (I would never leave that second chuck spinning without the tailstock).

Bill Boehme's suggestion of two good tenons would be easier, but this might have an edge in repeatability.

 

[Robert D Evans]

Every time you remove a piece from the chuck, you're going to have to mess with it to get it aligned "good enough" again. Using a properly made threaded glue block, it will screw onto the spindle and be exactly where you left it. Glue blocks are a lot lighter than a chuck too. Using two opposing glue blocks will necessitate you to create the second one while attached to your blank to guarantee alignment.

An 1 1/14' x 8 Bealle tap will be about $35.

 

[Mark Jundanian]

@Bill Boehme to your solution I would add this idea. Rather than leaving in the center of each tenon a simple shallow dimple for the 60* cone center that is relatively easy to "remodel" when remounting, I would drill a 60* recess, say a 1/4" deep, to fit the cone more definitely.

 

[Larry Copas]

A few years ago I made a live center with 1-1/4-8 threads to put a 12" diameter cone on. Later I started turning "snakes" about 32" long, 1" in diameter in the middle and tapering too near nothing at the ends. Had lots of trouble with vibration even with a steady rest. I found the only way I could turn the wood, was to put it in a chuck at the headstock and another chuck in the tailstock. Adjust the tailstock pressure to close to neutral and I could turn my snake and hardly needed the steady.



Another use is urns. The segemented urn is glued to a glueblock on each end which in turn is attached to a small faceplate. I turn each half the usual way than glue the halves together. After gluing I go ahead and turn the urn to completion. I could have used chucks on each end just as well but the glueblock probably is a little more rigid.

I think one of the store bought live centers would work just as well, but I like having my 1-1/4 threads on my home made center.

Thought my rambling might generate a thought or two.

 

[Mark Jundanian]

@Larry Copas , curious how you built your own live center.

 

[Bill Boehme]

I really like the solution presented by Larry Copas. A couple small lightweight aluminum faceplates screwed to wasteblocks probably means no need to spend money on yet another dust collector for most of us ... or am I the only one with a pile of infrequently used faceplates? (Not that there's anything wrong with buying new toys).

View: https://www.youtube.com/watch?v=Oj3VphK9AMk

 

[Larry Copas]

@Larry Copas , curious how you built your own live center.

I'm a shade tree machinist with a couple of metal lathes, Bridgeport, and several other machines. The live center is just a clone of the Oneway only bigger with a couple of minor changes.

I make a lot of my own stuff. In that last picture the dust hood mount, the handle on the banjo, and the aluminum faceplate are all home made.

 

[Don Wattenhofer]

I'm a shade tree machinist with a couple of metal lathes, Bridgeport, and several other machines. The live center is just a clone of the Oneway only bigger with a couple of minor changes.

I make a lot of my own stuff. In that last picture the dust hood mount, the handle on the banjo, and the aluminum faceplate are all home made.

Same here I have a LaBlond lathe and a Bridgeport and I can't understand how people can do without these machines. The metal working machines aside from being handy to make jigs for wood working can also be used for many wood working operations. The Lablond lathe was used to make an adapter to mount my wood turning scroll chucks so that I can cut threads in my turning using the thread cutting capabilities of the metal lathe. The Bridgeport mill makes a superior overarm router or drill press plus I have a spin index fixture that I can use to make hex heads on wooden bolts.

 

[Bill Boehme]

This thread has been moved to the Woodturning Discussion Forum.

 

[Jason Goodrich]

A simple aid for remounting that you may already know is to mark your item so you know which jaw should go to which part of the tenon. You might gain a little bit of accuracy doing it with the two chucks or two threaded glue blocks, but lining up the jaw to the tenon is going to be well within the margin of error you would have no matter what from wood movement.

 

[GRJensen]

This thread brought me to the realization that I needed additional hardware to do a tailstock mount on my second lathe. I have two, near identical, vessels in progress now and a tailstock mount for my PM2014 would come in handy, so I ordered a Oneway Live Center Adapter. Does that makes me a member of the "One Tool Away From Greatness" club?

 

[Gary Beasley]

One step closer to it!