Creating a sphere

or at least creating a perfect half sphere on a metal working lathe - how would I do that, is it possible on a non cnc lathe

If you change your mode of thinking from 'creating' a sphere to 'generating' a sphere, it may give you some insights.

You do not say whether you want a concave hemi-sphere or a convex hemi-sphere.

On a standard lathe, how do you generate a cylinder? You move a tool in a straight line parallel to an axis of rotation.

How would you generate (the frustum of) a cone? You move a tool in a straight line not parallel to an axis of rotation.

Thus, how would you generate a sphere? You move a tool in a semi-circle against a rotating workpiece.

Look up 'ball turning' or 'radius turning' in relation to lathe work. A tasty example of the idea is made by Holdridge.

Hi Justin,

Depending the size of sphere, have a look at Joe Pie making canon balls for his model on You Tube.

Small sphere I would use a form tool, larger a ball cutter both should get you very close. I;ve also used co-ordinates to form round section flywheel rims etc blending the cuts with a graver and file.

A radius forming tool, will generate a sphere.

The "Outer end" , and part of the "inner end"of the sphere is generated first.

The Inner end is gardually exstended until the sphere is parted off.

Life is agreat deal easier, if you don want a complete spher, but can live wiith a flat at the inner end, because the workpiece can be drilled and tapped and mounyted on arbor before using the radius turning tool.

Our biscuit barrel has an aluminium spherical knob which replaced the plastic one which cracked.

One of my "crowd pullers" at local shows is a small luminium sphere which will float and rotate on a 5 psi compressed air supply. It is homage to "The Rolling Stone" which can be seen, much larger, in a streetb in Luxemburg.

So, even with my limited skills, it can be dome.

Howard

For small spheres drill a hole the diameter required in the centre of some silver steel, then form a cutting edge all round. Mount on a wooden handle and use freehand (keep it moving) to true up a slightly oversize roughed out ball.

The Pittler lathe can do this type of turning without any additional equipment, I'm currently trying to turn a 2" ball and then cut a thread on it which follows the profile

ball turning on the Pittler

If you Google Ball Turning Tool you will find a variety of attachments available for most lathes. Basically a tool bit mounted on an adjustable pivot and operated directly by a hand lever. They used to be a favourite DIY project of MEW types but these days are available cheap to buy from the usual suppliers. Many can be adjusted to turn large and small balls, or half balls, and concave as well as convex curves.