North1, Do you have a clamp-on AMP meter, this may have already been covered. If you do you can check to see how much each circuit is drawing and from there you can decide which circuits to combine to free up a couple of location.... Or just run another set of wire off of your welding circuit breaker to your lathe, I'm not positive but my guess is that a 40 amp circuit will do just fine. And your not going to be using them both at the same time.
Here is an inexpensive clamp-on, I can't vouch for the quality but I'm sure for no more then you will be using it, I bet it will be fine.