@jeffmorris Whats a few hours here or there per bracket... in a few years you will have enough Actually, it sounds good... post a pic or two of your effort.

Depending on your CNC router, and probably more the bit type, I think plastics should be fine as long as they don't melt. And aluminum can actually be cut fairly well with most fine wood blades... not as sure about side cutting bits, but go slow on a test piece with a bit you don't mind testing with. DIY brackets are one thing where having a 3D printer can come in very handy

Ebay has gone heavily commercial... stick within the USA (for starters), with highly rated stores and always pay with PayPal. You should not have problems... or at least you can get you $$ back if you do via PayPal. Also watch the shipping costs... some sites pad their "low" price with high shipping.

I know that there are different kinds of plastics. I used ABS plastic sheets for the servo brackets. Which kind of plastic is best? I don't have a 3D printer.

Abs and pvc are the strongest and most expensive. However acrylic plexiglass will cut easily between 4 and 6 thousand rpm and it is easy to heat up and bend acrylic. Acrylic plexiglass is more than strong enough once you bend it into the shapes like c brackets. 1/4 inch for heavy duty torque . 1/8 " for regular brackets.

I thought that acrylic plexiglass can crack if too much force is applied to it.

Any plastic can Jeff but I'm betting you don't have a servo strong enough. For a standard servo use 1/8" and any high torque servo 1/4" plexiglass.

I meant that acrylic plexiglass can crack if you tighten screws too much.

You predrill all holes properly to the size of the shaft of the screw. When holes are properly predrilled you will not have that problem. I work with plexiglass and other plastic often and it works great.