Home
Gallery
Tools
Articles
Video
Links
Susan Rosand
About
Having a ball turning Shperes

Having a Ball Turning Spheres

I always liked turning spheres, but was never very good at it. About eight years ago, I read an American Woodturner article by Christian Burchard and tried to master his sphere technique. Unfortunately, my results were slightly lopsided.

Later, I watched Brian Simmons turn a perfect sphere using a PVC ring. Cool! But hard as I tried, I was not much better at making spheres. Recently though, I was forced to take another turn at spheres when a friend asked me to make several spheres for gifts. I hadn't turned a sphere in a couple of years and really didn't want the job, but I agreed to do it.

To make the first sphere, I drew a paper template for the size sphere I wanted, then placed my stock between centers and tried to cut away everything that didn't look round. That method worked, but not very well and it certainly wasn't very efficient. Finally, I went back to old issues of the American Woodturner and reread everything written on the subject. When I went back to the lathe, I finally turned out some fairly decent globes!

Several options for cup centers
Cup Centers Choose one of these affordable cup center options for your spheres: conventional live tail center, left; custom machined larger version, center, and cup center turned from 2" oak stock, right.

If you don't want to sacrifice a tail center for this job, you might review the Christian Burchard article {American Woodturner, June 1995}. Christian used a piece of dowel stock drilled to fit his tail center, with a cup on the other end, If you don't have access to a copy of the article, send $1 and an SASE to the

American Association of Woodturners
3499 Lexington Ave. N., Suite 103
Shoreview, MN 55126
(651) 484-9094

I spent the next few days turning nothing but spheres and actually enjoyed the process. I'm not sure whether I had become a better reader or a better turner over the years. Regardless, my results improved. And taking several days to practice and master the technique helped.

What follows is the method that I came up with to make spheres. Trust me, I didn't discover anything new. The only possibly new twist is using a vacuum chuck to hold the globes for sanding. You don't have a vacuum chuck? No worry! You really don't need it: It just makes the sanding process go faster.

One of the nice things about making spheres is that you don't need many tools. You'll need calipers, a small spindle/bowl gouge (3/8" or 1/2" spindle or 1/4" bowl gouge), and a 1/2" skew. Some woods also require a roughing out gouge. This project requires a simple cup chuck (see box at right), if you don't already have one.

First, make a blank with two tenons

Photo A With a rough out gouge, shape the cylinder. Note the 1" diameter tenons at both ends of the stock.

To make a 4-1/2" in diameter sphere like the one shown here requires rough stock about 4-1/2 ' square by about 5-1/2" inches long (Photo A). The extra 1/2" on each end allows you to leave small tenons on the globe that you'll later remove using a handsaw. The tenons are necessary because they give you a little room to work as well as preventing the spurs on the drive and tail centers from marring the finished piece.

Place the sphere stock between centers and use your roughing out gouge to turn it to a cylinder. Then take your calipers and determine the thickness of the soon to be globe, in this case 4-1/2". Mark two pencil lines on the sphere to indicate the maximum diameter of the globe. You should have about 1/2" of waste material beyond the pencil lines. Now, use your 1/2" skew as a peeling tool to remove the material beyond the two outer lines that marked the maximum sphere diameter. You'll have two tenons about 1" in diameter.

Photo B
Begin to shape the globe with a small bowl gouge or 1/2" spindle gouge.

As shown in Photo B, use a small bowl gouge (my choice) or 1/2" spindle gouge to remove everything that does not look like a globe. At this point, the sphere does not have to be perfect just approximate. With practice, your skills will improve.

As I wrote this, I recalled a David Ellsworth course. We needed to turn approximate spheres in preparation for hollow turning. I could never do any better than an oval shape, which significantly reduced the size of my hollow form when I finally got it round. The look on David's face as he observed my "masterpieces" was priceless.

Photo C
The sphere with tenons removed is ready for mounting between the cup centers.

Once you've roughed out the sphere, take it off the lathe and cut off the tenons with a small handsaw (Photo C).

Watch your sphere take shape

Photo D
Rotate the sphere 90° to the tenons, and then turn away the shadow to work the sphere to perfect the shape.

Now the fun part begins. You need to rotate the piece 90° and place it between two cup centers for turning. My cup center is about 2" in diameter and is held in my Talon chuck (Photo D). I drilled out most of the interior of the oak cup with a Forstner bit, removed more of the interior and rounded over the cup with a square nosed scraper (see Cup Centers box). The cup center on the tail stock side is a conventional live tail center that a machinist friend modified into a cup center. It works beautifully.

Remount the piece on the lathe between the cup centers, turned 90° from the direction it was held between centers for roughing. Turn on the lathe at a slow speed just to make sure that the sphere doesn't fly away on you, and then slowly increase the speed. You'll see the out of round areas create a shadow effect.

Carefully, turn away the shadow, and then stop the lathe. Rotate the piece 90° again and again turn away the shadow.

After doing this a few times, the piece should be perfectly round.

I am in perfect agreement with Christian that some pieces seem to forever resist going round. What I have discovered is that after sanding, a sphere that is not absolutely round cannot be distinguished from one that went round a little easier.

Photo E
With a vacuum chuck, hand sand the sphere, rotating the sphere 90° each time you change grits.
Photo F
If you power sand, work up to 600 grit smoothness before applying finish.

Watch your sphere take shape If you have a vacuum chuck, sanding these spheres can be an absolute joy or at least as much legal fun as you can have sanding. For my sanding procedure, I place the sphere in the vacuum chuck, sand, rotate the piece, sand and so forth until I reach about 320 grit smoothness. (Photo E). Because power sanding (Photo F) is so superior to hand sanding, I generally drop down to 220 grit, then power sand to 600 grit smoothness. Follow this up with a sanding sealer, two coats of an oil finish, and then wax.

If you don't have a vacuum chuck, a simple jamb chuck will suffice. Another solution is to sand the piece between the cup centers, rotating it as needed.

That's the basic sphere. Where you take it from there is up to you. Once you get the basic technique down, spheres can be a lot of fun. Give it a try, and as usual, if I can help, contact me.


This article originally appeared in The Journal of The American Association of Woodturners
Volume 18 Number 2, Summer 2003.