On Sun, 15 Mar 2009 09:09:15 -0700 (PDT), Mike wrote:

I've been looking into getting a new table saw, and since I only have
110v in my shop, I've limited my choices to contractor and hybrid
saws. I started wondering about the possibility of pulling 220v into
the shop and did some poking around in my breaker box. My circuit box
has the old style 'pushmatic' breakers and is completely full, so
adding a new 220v breaker really isn't an option. So, now I'm
wondering about tying into an existing 220v circuit.

There are two 220v circuits: a 30 amp for the air conditioner, and a
50 amp for the dryer. I don't think that using the air conditioner
circuit would be a good idea, especially in the summer. But, the dryer
circuit looks like a good possibility - assuming that we don't run the
dryer at the same time as the table saw. I was really surprised to
find that the dryer circuit was 50 amps - how much power does a dryer
really pull?

So the question is, is it OK to branch off of the dryer circuit and
run it out to the shop? Would it be OK to run a table saw on a 50 amp
220v circuit?
Run a disconnect. It is a separate switched fuse or breaker box,
connected directly to the main buss. From there you can run an
"expansion panel"

Or remove one of the 220 brekers and replace it with the largest you
can get and wire the "expansion panel" to that breaker, installing a
breaker for the original 220 volt load in that panel.