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CNC Mill Slide

A neighbor is a computer person and wants to build a CNC milling machine. He’s a genius at computers but weak in mechanics so I came up with this first stage slide prototype for him to review. I used the usual u-bolts and ball bearings which gives great precision with zero play, and all you need to build it is a drill and a hacksaw. It’s scalable so he can make it bigger or smaller. Everything comes from McMaster Carr.

The square tube is supported on the cross angles which ride on bearings on the ½” diameter rod. The rods are held together by the cross angle pieces at their ends which are in turn tied together by ¼” all-thread tension rods thru the tube. I cut pieces of thin-wire coil spring stock and slipped them over the u-bolts and then placed the ball bearings over the spring stock – this holds the ball bearings in place on the u-bolt.

How stiff is it? When you are milling, the cutter really wants to move the table around.
What does he plan to mill? If you are looking for CNC software, its hard to beat Mach3 for the price.
Looks like a fun project.

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Parts left out cost nothing and cause no problems!!

Yes, stiffness rules in anything that has to machine. The main elements are the 1/2" rods. The rest of the thing is stiff relative to them so they dictate what size of motor this will carry. When I learn more about what he has in mind, I can fine tune it. As I mentioned, it is easily scalable and I can go to bigger rods.
This thing really tracks true. I want to modify the design to get intermediate supports for the slide rods for more rigidity. You can never be too rich, too thin, or too stiff.

1/2" rods are going to flex like crazy.

I'd spend more and get linear slides from ebay.

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Noah

A plywood and all-thread milling machine?
So your tolerance is + or - what, .050" in plastic or soft wood?
Better to pick up an older REAL CNC mill with a dead control and retrofit it.

If you are in the east you could just get a working CNC mill on the cheap.
I recently passed up an excellent Matsuura 500V for UNDER $3000 because the shipping to me would have been more than that.

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If I must be a one-man PC free zone, so be it!