Typically, the bar is made from mild steel that can be easily cut using a hack saw or a dremel with a cut-off wheel. Or you can simply use a file to make a flat to receive the cutter. The notch doesn't have to be large - the usual target is for the notch depth to be about the thickness of the cutter. I usually also taper the nose of the bar at the sides and bottom using a grinder - the idea is to make the edge of the cutter extend over the bar at the nose and sides, and also taper back the bottom of the bar so that it won't wedge against the piece with the tool is being used.
Drilling is also fairly simple - you can use a hand drill, but a drill press is better. Drilling steel is much slower than drilling wood, and you have to periodically have to lubricate the drill bit with a light oil, so clamping the bar to a drill press table simplifies the process of keeping everything aligned for drilling and frees up a hand for fussing with an oil can.
Tapping is also fairly simple, but requires some practice. The hole is fairly small so you will be using a fine tap, and - DAMHIKT - small taps tend to 'wear out' frequently, especially if you haven't done this kind of work before and aren't practiced. So buy a spare tap (or two), use plenty of oil, and take your time. The tap will tend to bind in the hole, so you have to frequently back out the tap to clear the swarf. With small taps, you shouldn't try to cut more than a quarter of a turn at at time without clearing the swarf.
Turning definitely has it's issues but hopefully this will get better with the next two. 3/8 " bar stock, cherry and purple heart. Handle turned with the tool it now holds.
