Oval turnings

[Jim Maxwell]

I have been making segmented pieces for a while now. Have also been playing around with oval turning and building a wooden chuck to turn ovals. Then it dawned on me, why not combine the both? The photo shows the finished project. First one is of the "thing" complete, and the second photo is with the lid off. The real challenge was developing the angles and sizes of the segments. Dimensions are 125mm high, 90mm x 75mm.
Jim

[Claude Arragon]

Well done Jim
But to the the right measurement of the angles and size of the pieces, for turning an oval shape must have been kind of a challenge

[Bernie Weishapl]

Great job Jim. The piece looks great.

[Steve Busey]

Very nice! How about a picture of the chuck as well?

[Steve Schlumpf]

Impressive! I believe this is a first for me - never seen an oval lidded box before! Very nice work on the joints! Looking forward to seeing your next turning as they are all unique!

[Tom Sherman]

An oval box, from a lathe Cool, That's one I would like to see in progress.

[Jim Underwood]

I second the request for a picture of the chuck!

[Jim Maxwell]

Thanks folks for the nice comments. I can offer a series of photos of the chuck used to make the ovals. This one is the latest of four models. I am planning to build a fifth using brass or nylon for the moving parts. Because this is uncharted territory, progress is slow. It will have to be in a serial fashion as I can only post two photos at a time.
Chuck.JPG
This photo shows the chuck complete. It is built from 16mm backing board, and all the working parts are made from Cooktown ironwood soaked in a lanolin based oil.
ovalchuck2.JPG
Here I have removed the cover. The remnants of the last job are still visible.

[Jim Maxwell]

Now the faceplate has been removed. The centre rectangular plate is attached to the spindle of the headstock and rotates between the two outer runners. These runners have two aluminium bearers attached to the back, and they make contact with a bearing.
ovalchuck3.JPG
The next photo show the two aluminium bearers.
ovalchuck4.JPG

[Jim Maxwell]

This photo shows the bearing, attached to a ply plate. This plate moves horizontally to control the difference between the major and minor axis.
ovalchuck5.JPG
This photo show an oval lidded box made from silky oak, probably known to you people as lace wood.

I don't think I did a good job of setting this post up. I am much better behind a lathe than in front of a key board. Thanks for your patience..
Jim

[Jim Underwood]

Well, I'm quite impressed with your ingenuity and appreciative that you posted this here...

I'm still puzzling over how it works though.

I'll be burning sawdust until I figure it out....

I would think that the thing would bang back and forth instead of making a smooth oval....

*So I printed these pix out, and puzzled over them til I figured it out. (Told ya!) But now I've got lots of questions...

Does the shaft go through the spindle of your headstock? And how to you center this thing if so? Also, what's the shoulder on the shaft for? I can see how the large bearing plate is adjusted to set the minimum axis, and how the outer plate is moved by the rotation around the bearing, but what makes the whole carriage move back toward the center? Gravity, spring pressure? And how do you figure out how much space to put between the aluminum carriers?

[Jim Maxwell]

The only reason i am answering your questions is because of your name.. (just joking)
Jim, the shaft does go through the head stock and is fastened with a nut on the outside end. The shoulder on the shaft comes up against the nose of the driving shaft for positive location. This rotates the centre plate in photo 3. The slides on either side of the plate are attached to the aluminium bearers. These bearers ride on the bearing, which is off centre. The bearing, being off centre forces the aluminium bearers, slides and the face plate to oscillate in an elliptical path. The tool rest is at a height in line with the lathe centre, minus the thickness of the chisel. At that point there is a 'sweet' point where the job does not 'wobble'. That is where the cut is made. I generally use a scraping technique but can 'cut' except that the point of coantact must be at the 'sweet' point.
Best you visit me and I can show you in person....
Jim

[Jim Underwood]

Much as I'd love to come visit, I'm not sure my little Honda Civic would make it very far....

How about a video instead?

I printed out the pictures last night and really studied them, and I realized the whole key was your adjustable bearing plate - around which the whole eccentric plate revolved. I see how this makes the moving plate run back and forth to get your oval...

My biggest question is this - how does the mechanism "return" to a neutral position after the aluminum "carriers" aren't contacting the bearing anymore? Does centrifugal force do it? I don't see any springs.

And just how smooth is this critter? I can't see how it doesn't "bang" back and forth...

Oh... and was this your idea? Or did you pick it up from somewhere else? It's quite impressive in it's simplicity.

Thanks for the response.

[Jim Maxwell]

Jim, the aluminium carriers are in constant contact with the bearers and therefore there is no 'banging'. No I am not that brilliant, the idea has been around for well over 100 years in Europe. I got close and personal about ten years ago when I read a book written by David Springett, "Adventures in Woodturning", isbn 0 946819 57 2. Since building one by the book, I have built another two with modifications, with a fourth on the drawing board.
See if you can get your hands on a copy and it may become more clear.
Jim

[curtis rosche]

what does oval mean? what part is oval?