Alright, I am ready to give a bit of an update on this.
I pursued several leads on getting the brackets cut on a CNC mill. As it turned out, that is way more expensive that this project is worth. So, on to plan B. In my case, this was more like Plan K, but you get the idea. I hit on an idea that would have me spending less of my dollars and more of my time.
The thickness of the ring portion of the brackets is 0.248-9". Yup, 1/4". Funny how often metric stuff ends up being so close to an even English unit. Cold-rolled plate would work very nicely for this.
What I really needed was a way to locate the holes, and to secure the calipers. I used transfer punches to locate the holes and welded on a nut (M12x1.5) to hold the calipers.
I worked up a template by simply using Microsoft Word and the drawing tools combined with all the measurements that I had taken. I then printed it out, made sure the printer didn't stretch the drawing and then glued it to the piece of 1/4" plate. I think that I paid about $8 per plate including the labor to cut them. This shop is considered overprice, too.
I then used a hacksaw (
) to cut them out. I don't have a bandsaw, so here is where the extra labor comes in. It wasn't too bad actually. I was able to get good pressure on the blade by using a hand on each end of the hacksaw. I would guess that it took about 30 minutes each, including breaks, to get through it.
You will notice in the pictures that I cut through the ring to get the inside removed. I later welded up the cut and ground it down. I actually only did this on the first one. I figured that it would be less labor to drill a big hole and assemble the hacksaw inside, so that is what I did on the second one.
Time for some pictures, then on with the update...