Fabricating Clamp Collars / Shaft Collars with a Drill Press

This is how I make 1/4" and 1/2" aluminum clamp collars. A 1/2" collar is shown, but a 1/4" collar is the same except that it has only one clamping bolt. A drill press and C-clamps is a must for this, along with a 1" hole saw, tap, and the right drill bits. I like clamp collars because they don't mar the shaft, don't require a flat to be ground at any particular spot as set screw collars do to work well, and they seem to have higher clamping forces than set screw collars do.
I start with some stock 1/4" or 1/2" thick by 1" to 1.25" wide and punch it with a center hole .5" from the end and a clamping screw hole (or holes if I'm using 1/2" stock) .340" away from the center on the edge. I then drill the clamping screw hole all the way through with my tapping-size drill bit. I use 4-40 screws, so I use a #43 bit for the first all-the-way-through hole. I then open the hole up to the halfway point where the hacksaw split cut will later be made using a 7/64 bit. Finally, I open the hole up again with a (3/16"?) bit, just big enough for the bolt head, leaving about .1" of 7/64ths between the bolt head counterbore and the to-be-tapped #43 hole. You can see this in the lower hole in the above right picture. The top hole has had the first and second drills, but not the bolt head counterbore yet. Then I tap the holes for 4-40 thread.
I open the center hole up to something a bit under 1/4" and then, making sure the piece is clamped very solidly, go at it with a 1" hole saw. It's not shown, but I also clamp an aluminum heat sink block to the piece because hole saws try to get hot. I go slow, use oil, and don't let it get very hot. I go until I'm almost all the way through. If I remember, I don't unclamp the piece for the next step, but I unclamped it here to take the pic.
Drill the center hole. You want this to be as close to the shaft diameter as possible. I like to open holes up gradually, 1/16" or even 1/32" at a time. You might want to offset the center hole away from the clamping bolt, or leave it in the center. The one shown above is good in that I didn't have to slot the part opposite the clamp screw. 1/2" thick aluminum is strong enough that you may need to make part of the collar thinner, depending on the shaft diameter. You can do this by slotting it partway through with a hacksaw, or offsetting the center hole.
Cut the slot and test the collar out on the shaft. If it's hard to clamp, you may need to slot the side opposite the clamp screw partway through. Finally, what I do to make the collar's face nice and flat and even so that it works well against a thrust bearing washer (which is the entire point of all this) is tighten it on a piece of shaft stock in the drill chuck and then gently spin it against a clamped flat file. Presto! A $2 clamp collar with only a few hours of work! :D