Musing about shop made variable axis chucking methods

Store-bought eccentric and multi-axis chucks are expensive. I've never used one, but I understand that they work well and are easy and precise to use. My cobbled messes work to a degree, but commercial chucks are probably much more useful and convenient for changing eccentricity or shifting axes in measured steps, plus being able to return to any one step. BUT, some cost more than a quality mini-lathe!

My eccentric chucks are nothing more than a machinist faceplate with a radial slot for a dog. I used a shortened pipe tap moved along the slot to hold the blank and vary it's eccentricity. I can drill an accurate hole in a blank for a tap much easier than I can turn an accurate tenon for a die, but either a hole for a tap or a tenon for a die allows for _cutting threads. Much better for securing wood than the crushed threads made with a bolt or the headstock spindle. I also used a tailstock center or a rotating backing plate when possible.

I've sharpened and ridged the jaws of an independent 4 jaw wood chuck. Adjusts and holds pretty well for eccentrics. I've also slit a 2.5 in. length of 2 in. pipe into 4 sections and inserted them into the 4 jaw chuck as deep 'jaws'. I can round the end of a blank and move it off the spindle axis and hold it there in these 'jaws' or in a scroll chuck with deep jaws. Adjustments are limited and a pain to make. As for precision, forget it. It's true, "You can't go home again" nor can you go back to a previous axis with this set up. :)

I've thought about scribing concentric lines on a face plate and drilling holes on the lines , but scattered about the radii so they don't overlap. A screw or small tap could be attached to the various holes for holding the blank on different eccentric axes. Seems like a lot of messing about with imprecise adjustments.

Sorry for my tedious and confusing description. Do any of you have (or can suggest) other cheap homeshop chucks or methods for holding a blank on variable axes with convenient and fairly precise adjustments. If so, how do those of you bereft of pricey factory chucks do it?

Turn to Safety, Arch Fortiter

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Reply to
Arch
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Arch you've been reading my mail :-)) I am about to turn some oval door knobs for a stage set using forced perspective. Each knob gets smaller the farther away from the audience. So far I have come up with just using 2 jaws in a 4 jaw scroll chuck. I cut a rectangular tenon on the end of each piece so that I can slide it in the jaws and allows me to mark the centres with a sharp pencil along the edge of the jaws. Tun between centres with the same offset each end then move onto the new centre and so on. So far so good. I kind of got the idea from Ken Grunke's eccentric chuck here

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For more on forced perspective see here
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Peter Visit my site at:
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Reply to
Canchippy

Hello Arch,

Sounds like you've sort of run the gamut of home made ways to cobble up for eccentric turning. As a renouned tool-a-holic, I own most if not all of the eccentric chucks on the market and only a couple of them let you go back to an exact previous setting.

I have also turned faceplate work eccentric by using multiple holes and a screw chuck faceplate into a glue block on the workpiece. You do have nearly precise return to previous positions, but your offset can't be to excessive or you will tear out the screw threads in the wood. If possible one should use the tailstock to help support wood like this.

I have at times used my Nova Chuck with the 35 mm tenon jaws, which have serrated teeth inside the jaws, to do eccentric turning for goblets, etc. You have fair control of the amount of eccentricity once you have clamped it down onto a tenon.

I do more oval turning of hammer handles between centers and have demonstrated that locally and in Australia and New Zealand many times, but have only made one oval hammer handle for an actual hammer(which was for my wife's hammer when she broke the handle and wanted one out of Lignum viate).

Each of the commercial eccentric chucks have their merit. My first one was the Robert Sorby Eccentric Chucks, which shifts the wood sideways with a rotating eccentric disk that the wood is mounted to. I've since purchased the Escoulen ball and socket chuck, the Axminister eccentric chuck, one that is made by a fellow in England with different mounting holes (can't remember the name at the moment), and for Christmas 2005 my wife purchased the new Escoulen chuck which combines the ball and socket with the portion similar to the Robert Sorby chuck. This thing has many more adjustment options than I have imagination. I covered all of these except this last one in my book, "A Guide to Work Holding on the Lathe", which is available from Amazon.com.

I hope this rambling adds to your discussion.

Fred Holder

Reply to
Fred Holder

I have built a couple of vacuum chucks that allow for a variable axis. I got the idea after watching a demo by Escoulen. His chuck holds the wood in a ball and socket clamp, causing the spindle end to stay on axis, while the other end orbits. The axis flies around on a conical path.

The first chuck I built had a convex spherical surface, and vacuum, so the wood could be moved off axis just like his. However, I made a change which I think is actually better than his. I changed the convex spherical surface to a concave one. This means that as the wood is moved off axis, the cone faces the other way. The end that is orbiting is close to the chuck, and the tip of the cone is on axis near the tail stock. This means that I can turn an off-axis piece with both ends securely held.

I never got as far as providing for indexing the piece, but I think it could be done fairly easily by making circles and degree marks on the spherical surface.

In case you are wondering, I attach the blank to a bowl-shaped piece, and stick that to the vacuum chuck.

Reply to
Leo Lichtman

Grunke's faceplate / wormscrew arrangement looks nice.

Reply to
Bill in Detroit

Hi Bill

Get the coffee on, here's a few looks and info.

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Have fun and take care Leo Van Der Loo

On Apr 5, 12:44 am, Bill in Detroit wrote: /snip

Reply to
l.vanderloo

Hi Arch-

If you like, I could program and run you one of these if you've got some specs in mind. Setting my machine to run it while I'm at lunch and would otherwise be idle wouldn't be much trouble at all, and I could get those holes located for you to within .001". Also, after seeing the thread on the Longsworth chucks from a while back, it has given me plenty of interesting ideas.

For instance, if you wanted finer adjustment, I don't imagine it would be too much trouble for me to draft and cut a spiral slot in a disk with periodic etched marks to use as reference points for your various axis. A tight spiral could produce very fine increments of adjustment, but there is a limit to how much material could be removed before the disk becomes too weak, and unsafe to use. I'd imagine that one time around the disk, going from near the center to somewhere near the outside edge would be pretty useful, though.

Let me know if you want to look at this more closely, and we'll take it from there.

Reply to
Prometheus

Thanks Leo ... all I had to do was be reminded of the name "rose engine" to go looking for this article. Near the bottom you'll find plans and even a parts kit.

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Looks like, due to the complexity, work made on such a lathe might well fetch a serious premium. I'm in. It might take me a while, but I think I may have found my niche that will get me past a jury. Bill

Reply to
Bill in Detroit

Even the Escoulen chucks recomend completely finishing the area you've just turned before changing the orientation of the work because you will not be able to return exactly to any position once you've moved from it. So precise adjustments aren't part of woodturning.

If you already have a chuck with a couple of sets of jaws you're pretty much there for changing the axis of rotation. Chuck up a blank, turn 3/8th to 5/8ths of a sphere on on end. turn grooves in it if you want to have some index references. Chuck the ball up and change center line orientation similar to the expensive ball and socket collet chucks. Cheap way to try this type of turning. Also great practice with a skew.

charlie b

Reply to
charlieb

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