1. because I thought I would need to make a bearing in which to rotate the spur gear. I did not.
2. Because one part seemed to require me to mill a slot that would destroy a big piece of CFC, which is not cheap.
3. The easiest way to make this part involved attaching one part to another and I really do not like the threaded insert approach to making threaded holes in CFC.
But this morning, while waiting for church to start, I suddenly saw a solution. This is good because I need to make two more of these brackets to hold the slow motion controls for the Right Ascension and Declination axes. Machining this bracket out of a single block of carbon fiber would be slow and expensive.
I have avoided epoxying parts together because I like to make things that are repairable. This solution only requires gluing the vertical part that attaches to the polar axis housing and the horizontal piece that holds the stepper motor. The vertical part still has slots allowing vertical adjustment and the slots on the motor mount allow horizontal fine adjustment.
I used 1/2" thick acetal because I had a big enough sheet of it lying around and i wanted the extra stifness for thr weight of the stepper motor. I have some 3/8" carbon fiber sheet that I can use for the vertical and this stuff is stiff in a way that Delrin can only dream about. I am using 6-32 screws to attach to the polar axis housing so there is plenty of material on either side of that through hole.
The 1.09" slot I can cut using a .122" end mill. This will drop a .375" x 2" x .122" (or a little less) piece of CFC, for which I do not yet have a use but I will look for a way to use it
The horizontal component that holds the stepper motor is again 3/8" CFC, so far stiffer than required.
Also, for future blind hole threads, I think it makes more sense and easier to epoxy a 6-32 stainless steel stud into the hole and use a hex nut to bind two pieces together. Buying 6-32 stainless steel nuts and studs in small quantities seems to be difficult.
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