Listen to macbow! The breaker/fuse is there to keep you from damaging machines or more importantly from starting a fire by running too much current through too small of a wire. If it has a 20A fuse, I'm willing to bet your wire is not adequately sized for 30A. You need #10 wire running to all points on the circuit before you can safely put a 30A fuse in.
If you run a 100A circuit to your shop as Roy suggests and then put a subpanel in your shop you will indeed be in hog heaven. However, the wire required for 100A service is much heavier than #10. I think it's #2 for aluminum and #4 for copper, but you also need to consider length. Check your local regs first. If you do put in a sub panel, you'll need to keep your ground seperate until back at your main panel.
Easiest safe way to expand electrical capacity is to add a second 20A shop circuit. A lot easier than a 100A subpanel and much safer than increasing the current circuit with a 30A fuse (unless you really do have #10 wire everywhere.)
Good luck. -Dave