Lathe Spherical Program

[Species8472]

When programing a spherical on a lathe radius compensation is IMHO absolutely required. Our setup guy seems to think that using the X offset is enough to control size. I think that when you compensate for tool deflection using only the X offset you throw the spherical out of round. This is because there is deflection in both X and Z. So the only way to get a truly round spherical is to back off the radius compensation then bring the the X offset in until you get a round spherical then comp your way to size.

So what to you guys think?

[txcncman]

I would use compensation anyway, but deflection may not be equal for X and Z and would have to be adjusted accordingly (X, Z, and R offsets).

And, if you are cutting both leading and trailing sides, best to make 2 tool offsets to adjust both sides of sphere.

[Geof]

I have found the easiest way to get a true sphere is to use compensation and tweak both the X offset and the compensation radius. And as txcncman says sometimes it is necessary to use two tools but, depending on how far around the sphere you are going, I have found using a full radius tool, say 1/16" radius, can work very well on an easy to machine material like brass. On steel or aluminum it can be prone to chatter because there is so much cutting edge in contact.