I need advice about chuck/jaws for large lightweight turnings

[Zachary Hoyt]

I haven't posted in this forum before, but I am hoping that someone can advise me about what kind of setup I should get to enable re-centering of large fairly lightweight turnings. The diameters are mostly 8 to 16 inches, and the weights under 5 pounds.

I build banjos, and turn the rim (the round part) on a Shopsmith. So far I have turned well over 200 on faceplates. I bolt the little Shopsmith faceplate to the center of a larger disk of 3/4" particle board or 1/4" aluminum and either use screws to hold the blank to the faceplate, or in cases where the holes would be a problem I use hot glue. This works fine for a lot of what I do, but there are times when it would be nice to be able to take a rim off after turning it, and turn it around so I can cut a rabbet in the bottom side to accept a metal flange. I have only made a couple of resonators (the Frisbee shaped thing on the back of some banjos) but I'll be making another one next month, and for that it would be nice to be able to turn it around so I can turn both the inside and the outside. The resonators are a bit under 14" in diameter, so there's only an inch between the outside of the piece and the tubes of the Shopsmith, so I don't know if that's enough clearance to any kind of outside gripping jaws. I'll attach a couple of pictures to give a better idea of the kind of shapes I'm working with.

I have read about various kinds of chucks and jaws and things, but I don't have any actual experience with them, so I'm hoping to learn about what kind of thing would be best. My top priority is precision and repeatability of centering, in order to fit the wood rim to the metal parts it has to be pretty close. I hope to get an actual lathe in a few years, once I have a larger work space, so it would be helpful if whatever I need for the Shopsmith was also able to be adapted to a bigger lathe in the future, but that's not essential. Thank you for taking time to read this and for any advice you may be willing to share.
Zach

[Brice Rogers]

Zach, for the resonator (the thing that looks like a frisbee), have you considered using a vacuum chuck? I find that they hold great and if you leave a little dimple from your live center, it is easy to take off the lathe and re-register on the vacuum chuck.

I'm not sure about holding the rim and will let others opine.

[Zachary Hoyt]

Brice, thank you for the suggestion. I had heard of vacuum chucks but didn't know anything about them. I've looked into them a bit now, and it looks from the pictures I have seen like the vacuum line runs through the hollow center of the lathe shaft, and if I have understood that correctly I wouldn't be able to use it on the Shopsmith which has a solid 5/8" shaft. It's something I'll certainly want to keep in mind for later when I hope to get a real lathe and only use the Shopsmith for line boring and sanding. Thank you very much.
Zach

[roger wiegand]

When I made my banjo I used a jam chuck made from scrap wood to finish the rim. Cheap and easy, not the easiest if you need to do a lot of them but for an occasional one it's perfect and nearly free. It would also work fine for the outside of the resonator (mine was open back, so didn't face that issue)

Today I'd use my Cole jaws because I already have them. Vacuum chuck would also be a good choice.

[Brice Rogers]

Zach, I think that there are some adapters that would attach at the chuck end. The use a pair of sealed bearings to route the vacuum to the vacuum head. They may cost a bit more and there are only one or two suppliers. And it is doubtful that they would be able to be fit to the Shopsmith 5/8" straight spindle without yet another adapter. I didn't think of that when I replied. In case you're interested for getting ideas for something custom - - https://www.cwsonline.com.au/shop/ca...s--accessories

You're right that it is easiest to outfit a vacuum system with a hollow spindle.

[Zachary Hoyt]

Thank you both for the help, I really appreciate it. I've read of people using a jam chuck before, but as you said it seems to be more of a one-off thing, and I'm in more a low-volume production situation, I guess. I have been looking for Cole jaws and came across a set on eBay which is off-brand but looks like that sort of design. Is there anything about this set that makes a wiser person than me think they wouldn't be suitable? Thank you very much.
Zach
https://www.ebay.com/itm/14-3-4-Wood...w/371847686612

[Don Bunce]

You might want to check on the maximum speed those are rated at. THE Nova Cole jaws are rated at 600 rpm max.
Hurricane rates theirs at 500 rpm max.
The Shopsmith minimum speed is about 600 o 700 rpm IIRC.

[Zachary Hoyt]

That's an interesting point about the speed rating. I do all my rims at the lowest end of the Reeves drive on the Shopsmith, which is supposed to 700 officially, but I don't know how accurate that number really is as I don't have a tach to check it. I have a 16" faceplate that I use for large rims, and it's definitely faster than would be ideal but by working very carefully I have been lucky enough not to ruin a rim yet.
Zach

[roger wiegand]

I've found that the trapezoidal/rectangular urethane bumpers that come with the Vicmarc Cole jaws are much better than the round bumpers that come with other jaws. They form a dovetail that holds the piece in more securely. I don't know if they can be acquired separately and used with other jaws, but I'd ask

I'd be pretty leery of a no-name chuck off ebay. You can keep your chuck as you upgrade lathes, so it's a long term investment. Oneway and Vicmarc are examples of well proven providers of top quality tools.

[Zachary Hoyt]

That makes sense about buying a good one to start with. It looks like the set of 8 Vicmarc bumpers can be had for $48 by themselves. I like the design of the Vicmarc 120 chuck, but the jaw sizes don't work well with the Shopsmith, one size is too small to hold what I need to and the next looks to be too big to swing. I read that the Oneway Stronghold Mega Jumbo Jaws are 14" when fully closed, so that would be about perfect for the Shopsmith. It looks like i can get that chuck, jaws and adapter for about $360 with shipping, which will probably be worth it to me over time, and if I find that I can't get a secure enough grip I can always try the Vicmarc bumpers instead of the Oneway ones. Thank you very much for your help, I really appreciate it.
Zach

[Jeffrey J Smith]

For what you’re doing, it might be wise to fabricate a set of steel or aluminum bumpers for either the oneway or vicmark jumbo jaws. better hold if you need to remove a lot of wood. Easily turned and drilled from rod stock with hss tools.

[Zachary Hoyt]

Thanks, that's a good thought. I've done a little bit of that kind of work, so it should be easy enough. I'm not confident in my ability to accurately drill through the center, so I may get some heavy walled aluminum tubing and use that. I got a piece to make the tongue for a canoe trailer for my bicycle, it was 1/4" ID and 3/4" OD, or something like that. I'll have to look for what I can get with a 6mm ID, or 3/16" and drill it out to 6mm or something like that. I've ordered the Oneway parts and am looking forward to trying them out. Thank you all very much for your help.
Zach