Longworth chuck variations

[Tiger]

Having looked at some of the literature on Longworth chuck, I've seen them with 4, 6 and 8 slots. I would have thought the more slots and therefore the more holding units, the more secure the workpiece, but I've seen conflicting opinions on this. Other thing I noticed that someone said they can be used in expansion mode as well as the typical contraction mode. What do you think?

[Allen Neighbors]

I have two that I made... one for outboard and one for inboard. I put 8 slots in each. And if I were going to make another, it would be with 6 slots.
I've found that when I have a small bowl to finish, I have to leave off 4 of the buttons, to get it small enough (because of my poor engineering, with a large center piece), and 4 just doesn't seem to hold it tight enough for my poor technique of turning.
With 6 buttons, I use all 6 with smaller bowls.
And, yes, mine work well in either expansion or contraction... just depends on the style of bowl.
Just my .02. :)

[Tiger]

Thanks, Allen.

For the outboard version, do you rout the slots in reverse?

Have you had any problems with the expansion mode, ie things flying off?

[Texian]

Have used mine in both expansion and contraction also. Rarely use it now, preferring a friction, jam, or doughnut chuck as needed. Was often not getting adequate grip with the Longworth.

[hughie]

I have a couple of Longworth chucks and use them in both directions. With multiple gripping points you tend to lose on grabbing the smaller diameters due to the congestion of the slots at the centre. So my small one has only four grippers, whereas my bigger one had eight.
Usage, mainly for finishing the bottoms, like Richard I have found that they have a limit to what they can actually hold. Never the less a very handy tool in my shed and they sit along side a large donut chuck, with the Longworth and the Donut chucks you have got it fairly well covered in most events.

[Allen Neighbors]

Thanks, Allen.

For the outboard version, do you rout the slots in reverse?
No. It's just like the other one, only bigger. The front slots work against the rear slots on each Longworth, which makes the buttons roll around the arcs. I hit the reverse switch when turning outboard.

Have you had any problems with the expansion mode, ie things flying off?
Not a problem, if the bowl has an undercut rim, so the buttons can grip. The undercut rim acts the same as a dovetail cut for expansion mode with a chuck.


All I use my Longworths for is finishing bowl/plate bottoms.
That green is sure a pukey color, isn't it.... :;

[Tiger]

Thanks, Allen and others. I had made a smaller one but now need one to do anything 10 inches or larger.

[joe greiner]

More slots and more buttons provide gentler pressure on the rim. Six slots are easier to lay out with compass alone; the others require extra layout steps. Four slots/buttons led to grief on a small bowl once, but it's still usable for square rosettes.

Expansion vs. contraction depends on the rim configuration. Expansion is more suitable for undercut rims, contraction for flared.

I use mine mostly for bowl bottoms. For insurance against launching into orbit, I wrap strapping tape across to the back of the back plate; three or four tapes is sufficient. Adhesive remnants can be rubbed off without affecting the finish. Fold the ends of the tape back about 1/4" to provide a lifting handle for removal; this is a suitable trick for any taping situation.

Cheers,
Joe