It's rather simple to cut a keyway with just a boring bar and your carriage. It's a poor man's shaper. Put the correct profile bit in the bar, set where you want the slot, then advance the carriage by hand thru the hole to remove ~ 0.002". Move the cross slide out another 0.002" and move the carriage again, cutting another 0.002" out. Repeat, lather, rinse, until you have reached your desired depth. The lathe is NOT running while performing this operation and the spindle is locked in one position.