On-Site Machining Keyway Without a Keyway Cutter
Having a keyway cutter is handy, but what do you do when all of your machines are out and/or your keyway cutter is too small to fit around the shaft, and you get the call for an emergency keyway cut at 180 degrees to the existing keyway? Use a portable X-Y milling table, of course. 
Above you can see that we manufactured a quick and dirty (this was an emergency job) pedestal (gray) and V-horse (rust), welded the two fixtures together, and then tack welded the combined fixture to the floor. Next, we leveled out and bolted our portable milling machine to the fixture.
Above you can see that we are ready to start milling the keyway. In the foreground you see the rigid drive hooked up to the X-Y table, or "feed table" as we call them, to control the X travel of the table. The Y travel is controlled by an electric drive on the back end of the cross slide. The Z travel on this project is a fixed height, so we do not have a Z drive in place. The gray bucket adorned with duct tape is the coolant mister, which keeps the end mill cool while it mills the keyway.
Above you can see that the keyway milling is in progress, well on its way to being complete. The secret sauce in field machining is all in the setup.