Sphere - A yet untested method

Re: Sphere - A yet untested method

John K Jordan

>>In the very least, choosing this opposite corner method will result in the least wood wasted.

An interesting idea. It might be that the block would need to start out as a near-perfect cube in order to waste the least amount of wood. If wood had to be trimmed to make it a cube, it is unclear to me without further thought whether it would make a difference on the amount of wood saved.

Rather than flatten the corners, I envision the possibility of centers with pyramid indentations to hold the corners, especially if starting with a near-perfect cube. That would auto center. Re-positioning it three times to the other corner pairs and removing wood to the diameter with a parting tool might make a better starting point for the traditional cleanup, with four diameter rings instead of two.

Have to think about this or make a drawing or, gasp, try it. Yikes.

JKJ

Your method is fine if for decorative work only

Dick Coers

But if you need an accurate sphere, like for sport, your method would make it more difficult.

Re: Sphere - A yet untested method

Craig Daymon

A bit of lost logic in your understanding of the process as the other corners would be turned away following the first mounting, but if you get to trying it before I do, please report back.

Re: Your method is fine if for decorative work onl

Craig Daymon

I presume you mean accuracy with respect to size, as the method I described still finishes between cup centers and in so doing is quite capable of generating a very accurate sphere. (I'm looking at an Osage Orange sphere right now, which aside from being risky if I drop on my toe, is very true in shape...as much as any wooden sphere, subject to seasonal changes, can be.)

As far as size goes, if one wanted a sphere of say 3" in diameter, they could start with a cube fractionally greater than that and there should be no reason a 3" diameter sphere can be generated just as easily as with any other method.

To be honest, I can't see any method that would differ in this aspect. Unless you are skilled enough to turn one that would not require sanding, any sphere would have to start as a piece of wood larger than the target size, but I still see this one as having the least wood waste for those who are not to that point.

Even if you used one of the jigs to cut it to size, you would still want to put it between cup centers for sanding, which should be taken into account depending on your acceptable level of accuracy.

Sorry, typing off the top of my head. Tend to go on a bit.

Dimensionally accurate

Dick Coers

If you can turn a sphere by removing the shadows, and can turn six of them within 1/16" of nominal dimension for a croquet set, more power to you. I've turned quite a few and would not be confident of the outcome in my shop.

sounds very interesting

John K Jordan

Craig, this makes me want to try it even more. Do you have any intermediate photos? Do you make initial sizing cuts from all four sets of corners.

I will definitely try this and measure the starting cube and the ending size. I won't have time for a couple of weeks (I'm, as they say, a bit overextended at the moment) but it is second on my turning list.

I've been thinking of some ways to make concave pyramidal "chucks" for both ends as well.

Your method also gives me an idea for something entirely different. I want to try it before I spout off about it!

JKJ

Re: Dimensionally accurate

Craig Daymon

What method do you use that gives you dimensionally accurate results? (Putting aside that wood movement makes any wooden sphere only truly dimensionally accurate at the point of initial completion, or when temperature and humidity exactly meet those of the environment in which it was initially created.)

Does it in any way utiliize putting the sphere between cup centers? If so, even if just for sanding, I just can't imagine my method being any less capable of getting exacting results. Sure, using the method I suggest, you may have to start with a larger cube (probably will) in order to get a sphere of a lesser size. I certainly wouldn't cut a 3" square cube to get a 3" sphere as the saw cut and final sanding required to remove any saw marks, even if all turning was perfect, would still require a little extra size, but I believe less wood would be required this way..

Just trying to understand, and rambling on as usual.

Re: Dimensionally accurate

john lucas

Using the Carter jig i was able to get spheres within 1/10 of an inch or closer of each other. I have a friend who needed to do that so we borrowed one of the jigs from another friend and figured out how to not only get them round within abaout .010. we were able to almost exactly get the same size. Something I can't personally do with the between cup centers method but then I don't turn a lot of spheres either.

Carter perfect sphere

Dick Coers

I have turned them between centers and with a chuck with the Carter. Where I run into dimensional accuracy by turning off the shadows by hand, is that I never get it in the first return. I turn between centers, put it in cup centers with the stubs perpendicular to the bed. I usually find that I still have a shadow, and rotate it slightly to turn again. I loose diameter each time, and found I can't predict the amount that gets removed.

With the Carter, I have very little material to remove from the stub, and don't have to rotate it in the cup centers to clean up that little amount of material. I remove less than a 1/64 sanding it smooth. I really think I can get a smaller tenon left on harder wood and would not have to use cup centers at all. Just carve a little and random orbit sand it.

2 1/4" diameter soft maple

Re: Carter perfect sphere

Craig Daymon

I turned a sphere as I described it today. While doing so, I realized that there is no reason this mounting would not work just as well for the Carter jig or any of the other similar shop made/commercial jigs. (I remember a turner - maybe French - named Jacques Michelle, maybe Jeane - had a nice one and plans on his site. Don't know if all his jigs/plans are still about since his passing several years back.)

As it is the jig that is getting you that level of precision, might as well consider this mounting. Speaking of turning spheres, not pommels or spherical sections within a larger spindle.

My shop lighting (or general set-up) is not ideal (understatement) but the solid within the shadows did not appear to be quite the perfect sphere I had hoped for with the initial mounting. This may be largely due to insufficient lighting as this mounting will have many levels of shadows.

When the rough sphere was turned away the remaining stubs on either end from the corners of the cube where it was mounted were about 1.5 inches long each, maybe a little less, for a roughed sphere turned from a 3" cube. (If I think about it, I can use a little geometry to figure exactly what it should be. Shortest distance from the surface of a 3" sphere inside a 3" cube to the nearest corner of that cube.)

Re: Sphere - A yet untested method

mikeee12345

I have turned a number of wood spheres the past couple of years for use as a pattern mold for a guild.

I usually laminate wood planks into a cube and mark the center points on 3 axis prior to turning. I then

run the cube on a table saw and cut all of the corners down at a 45 deg angle to create a hexagonal shape

to reduce the amount of wood to rough out on the lathe. I also drill the 3 sets of axis points with a small

diameter drill bit so I never lose the center points while reducing the size of the ball. I also have a pattern made of wood that is sized for the OD of sphere you want to end up with. I rotate between axis points and remove the shadow and balance the shape. As I get close to the final dimension of the desired sphere I rotate between axis points and switch to sanding it round, rotating between the axis centers.

If you start with only (1) axis reference on your billet you can get it rounded and measure the exact center of the sphere and drill (1) axis reference and use a flexible measuring tape and measure half way around the sphere and drill your second axis reference point. This will gain you the 2nd set of centers to mount your sphere to turn the shadowed wood to balance the wood ball.