[Tywash]

Okay, I am retrofitting a Bridgeport Series I CNC. I am going to be running a
Galil DMC-1860 which in turn will be controlling 3 or maybe 4 (haven't decided yet) Compumotor Gemini GV-6U12e servo drives. I am having trouble looking for Nema 42 motors in the surplus market that will fit my machine and am now looking at buying them new. To be clear I already have these items and now just need servos.

My question is first does anyone has any suggestions for places I haven't looked to buy surplus servos? I have tried the various surplus stores and ebay with no luck.

Second question is I see servos have an option for 'brakes'. Is this something I want or need?

I have no access to a CNC machine to make parts that I might need to help my retrofit so this last question is just a shot in the dark. Is there an easy way to adapt Nema 34 motors to my machine? I know anything is possible, but I need something I can buy. I ask simply because this size is available everywhere.

These are the servos that I was told by a Parker distributor would be 100% compatible. Only problem is they are $1500.00 bucks a pop with cables. MaxPlus RotaryServo1141ASG.pdf PG.27 Maybe I am better off getting an old machine with servos already on it. Of course hindsight is 20/20.

[unterhaus]

if you can be patient and spend some time studying data sheets, you can find surplus motors on Ebay. The summer is the best time for that. I don't know the Gemini drives at all, Compumotor often is very rigid about matching motors to drives, i.e., my experience has been I need to buy a matching motor for a Compumotor drive. I haven't really been following Ebay recently, but Compumotor isn't one of the brands that I've seen a lot of recently.

[Al_The_Man]

Second question is I see servos have an option for 'brakes'. Is this something I want or need?
.

I don't think you will see a need for servo brakes, especially on a bridgeport.
With possibly the exeption of an index table, where you need to lock in place after indexing.
Al.

[PeteZ28]

I suggest the use of a brake on the Z-axis, whether you go with a spindle or knee mounted Z. Ballscrews can be easily back driven, and gravity is enough to drop a Z-axis. In the case of a knee driven Z, it could drop violently and probably damage something.

X/Y have no requirement for a brake.

On a related note, what size motors are good for this project? I'm planning a similar project right now. 400W? 750W? 1KW?