Still more on simple sphere turning aid

QED!

GaryG in MD

Nice job, Dennis.

I like what you've done in this series.

I do not plan to make enough spheres to buy a jig, but your procedure makes the process simple and easy to achieve a good result.

Bravo.

...GG

Re: Still more on simple sphere turning aid

Tom Albrecht

Thanks! And, that is a key point about leaving a "vestige" of the original line.

Reading instructions carefully

Doug Wolf

Dennis, I started turning spheres with a printout of your graph. Unfortunately I had the graph in my shop and your post with the instructions from April 11th on my computer in the house. I read through the text printed in the box on the graph and there was no mention to measure from "the corners", so I measured from the centerline I had drawn on my cylinder. I had glued up some different sized pieces of wood so I didn't have a smooth uniform cylinder and just marked a centerline for my sphere. It didn't look right but I was covered in shavings and didn't want to go to the house, so I started cutting. Needless to say I wasn't making a sphere. I went in the house and read your instructions I realized I should have measured from the corners, not the centerline. I won't forget this again, but the good thing is that I came up with a ratio for measuring from my centerline so my 70 year old brain cells got a good workout.

Re: Still more on simple sphere turning aid

John C Lucas

What i did for years was simply to turn it by eyè. Usually it was more egg shaped but seldom an accurate sphere. Then i would cut off the tenons and mount it between 2 cup centers and turn away the "air shadow". Then rotate 90 degrees and do the same, rotate to some other axis and repeat. It works but if your sphere is really off in the beginning you have to repeat this a lot to get it round. Also if you take off more than shadow every time you rotate it i. The cup chucks it will still show the shadow so your sphere gets smaller and smaller. Pretty soon you have a marble and you started with a softball.

Dennis's method gets you so much closer on the first try. Im also going to make new cup centers out of some white plastic rod i bougjt before i moved. I had made cup centers out of solid wood and theh move seasonally and oumpound the problem of the illusive shadow.

Re: Reading instructions carefully

John K Jordan

Doug, if you haven't seen it you might want to look at the Soren Berger video about this technique:

http://youtu.be/R4s5LziiS08

He uses his sphere caliper with the built-in ratios for the divisions but the method of marking and turning is exactly the same.

JKJ

Re: Still more on simple sphere turning aid

don stephan

Can't thank you enough for the interesting and stimulating posts on turning spheres. Haven't tried one yet, had too much fun trying to remember trigonometry and calculating the multiplying constants and making CAD drawings. Eventually I'll have it all written out, and then start practicing.

Have a large American Elm trunk that's asking to be made into some largish spheres.

Re: Shadow method

Doug Wolf

John, I turned these using the "Shadow Method" and they turn out fine but you wouldn't believe how BIG they started out. Every time I rotated them there was another shadow to turn away. I am hoping Dennis's method will reduce the waste.

Re: Shadow method

John C Lucas

I think the trick using the shadow method is to turn down to the solid woor and no more. If you dont turn down to the solid wood when you rotate it in the cup centers it will always show another shadow.

I think i also had a problem with my cup centers being slightly out of round because i used solid wood. I bought 3" solid plastic rod nust before i moved with the intention of making 2 sets of cup centers. One set for small.spheres and one for larger. I hope to get that done i. The next few weeks

Re: Still more on simple sphere turning aid

Craig Daymon

Haven't posted for a while now, but been following the sphere discussion a bit.

Totally agree with the shadow method. Unless you're turning the end of a column spherical or size is critical, the shadow method is simple and as I understand it with the approximation method (drawing lines, cutting consecutive angles) you are going to finish by putting it between cup centers anyway.

For a while, I started by turning, leaving a center flat ridge and then mounting between centers on the ridge, but this serves no real advantage to just getting close to a sphere between centers and then switching orientation to between cup centers and then reorienting and touching up until it looks round in multiple orientations.

I'm waiting on a 1.25"-8tpi spindle tap to make a cup center for the head stock and I already have a 3/4"-10tpi tap for making the same for the Oneway live center. Gonna use UHMW plastic from a 2" diameter rod I have. (Packard was the only supplier I found with the 1.25"-8tpi...aside from Amazon where someone wanted over $100 for one. Everyone else out of stock.)

Re: Still more on simple sphere turning aid

John C Lucas

Craig. I bought my plastic rod from either Enco or MSC. They had a wide variety of types.

Re: Still more on simple sphere turning aid

Dennis in Southern Oregon

Craig, FWIW, I use scrap Corian for making misc tooling and jigs. It is often available free from local bathroom fabricators. It comes in 1/2 inch sheets that can be laminated if necessary using epoxy and is easy to saw, turn and tap. It is dimensionally stable.

Re: Still more on simple sphere turning aid

doug williams

I saw a video once of a guy turning a sphere, after he roughed it out to round by eye he used a parting tool and made a groove right in the middle. After cutting off the ends and mounting between cup centers with the groove horizontal with the rest you could see a perfect circle, all you had to do was cut down to the line. A lot of starting and stopping to check but it was a easy way for me to do it and came out great.

Re: Still more on simple sphere turning aid

john lucas

Doug I had forgotten about that method. I tried that probably close to 20 years ago and used it along with the cup centers to turn a lot of spheres back in those days. It does work. I'll have to try it again. Coupled with the method Dennis posted it should really speed up turning spheres because you would probably just barely be out of round when you move it to the cup centers.

Re: Still more on simple sphere turning aid

Craig Daymon

I bought mine from Enco. Have bought from McMaster as well, though Enco generally has better prices. McMaster has better selection and great information on their site.