CNC milling spindle with belt-drive - construction

I am a total newbie to milling equipment but have been using woodworking and electronics for a while. Building a CNC machine that will be used both for milling and woodworking. I already have a high quality brushless motors and below is the design I came up with. The major problem is figuring out how to connect ER20 chuck to the ball-bearing spindle (rod) that will be driven by the motor. These chucks mostly come with a tapered collets that I cannot connect to easily. Is there a type of collet that would be feasible for my application? Is there a collet that already has ball-bearings and is ready for the belt-driven application below or would you recommend a totally different approach?

I know I can get a solution (contraption) that will help accomplish this for several hindered dollars but I was looking at a more cost-effective solution. It is just very difficult to find non-tapered collets and their detailed descriptions and hope you can advice a practical solution. thanks.

Attachment 239340

I found a straight collet chuck holder on Amazon with 20mm collet. the new idea is to get ball bearing (got these) with ID 20mm and put it directly on the collet. So, the collet will replace the spindle on the picture in the original post. Is this feasible? Any recommendations or warnings for the ball bearings? Any other recommendations on mounting? Thanks

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See if you can figure out a way to have easily changeable tools. Most machine tools use a tapered spindle that can accept tapered tool holders. Use an air cylinder to open the drawbar that hold the tool in the spindle. This system is reliable and accurate. You might have to design your own spindle shaft, with a provision for a belleville washer style drawbar. It would be a very good read for everyone on the forums and allow for a tool changer later on.

Thank you,

Phil

The devil is in the details.

Specifically, what do you mean by "ball bearings"?

Most milling machine spindles use expensive pairs of angular contact bearings to provide radial and axial (thrust) support. They are expensive because they are paired to work together to provide minimal runout but not over heat.

I suggest you search around on the zone for some other threads on building spindles from scratch (I know I have seen a few), as it is not something to jump into without prior experience. Searching for "DIY spindle" is a good place to start.

You said "milling and woodworking". Frequently those don't mix:
milling: need precision bearings with no runout, running at slow speeds (<5000 rpm).
woodworking: slop in bearings is okay, need bearings that can survive high speeds (20000+ rpm), like a router.