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My CNC Router
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John Rudd:
Steve,

Does this help with bearings?

https://www.ereplacementparts.com/bosch-pr20evsk-3601f0a710-colt-variablespeed-palm-router-parts-c-128_1119_33329.html?srsltid=AfmBOopUxtrY6NkKTrHyCzqClyLH4LAqOzx1AACN1fLo6Wu4MkHUfAoM
vtsteam:
Thanks Russell.  :beer: Thanks John  :beer: I ordered a set of bearings from the site you listed. Much obliged!

I think today I'll try fitting that 500 watt spindle to the mill, just to see what it can do. I did spend some time looking at various spindles in the $100 to $300 range on Amazon, and reading reviews and it wasn't very informative. Some were DC some were VFD 3 phase, some air cooled some water cooled. Seemed like the most expensive (water cooled 2.2 kw 4 bearing w/vfd) had comments like "not much torque compared to my ________" router, or even as much torque as the reviewer's old 300 watt spindle.

So I'm curious about this 500 watt DC spindle I already have. What can it do?

When I think about this stuff, I'm thinking it's likely I will probably settle on a 1/8" 2 flute mill bit for whatever I use this machine for in future. Aluminum, not wood. Small parts. That means to me, considering the overall stiffness of the machine, a speed probably where I am now - 8000 rpm 16 IPM, and depth of cut yet to be determined.

So if that's true, an ideal spindle would be running at 8000 RPM at its peak power output, not a 24000 or higher spindle throttled down to 8000. Bearings are obviously a major consideration. Ideally I would make up a non-motorized spindle driven by a belt of some sort, and a separate motor. Is that right?
vtsteam:
I've got plenty of high quality skate bearings (608 2RS) up to ABEC9 IRC. It wouldn't be hard to make up a spindle with some water pipe as a housing. I think I have some high quality 8mm shaft as well.

I was curious about what the RPM limit was for the skate bearings, and came across this explanation which I found quite humorous:

https://www.ahrinternational.com/Skateboard_bearings.htm
awemawson:
Steve, I made up a high speed spindle to use in my CNC milling machine many years back using simple bearing but it was driven by an integral air turbine (jet impinging on a small gear wheel), and I arranged it so that the air passed through the bearings downwords and kept the swarf off the workpiece. As the air was lubricated being supplied from a regulator / lubricator it not only cooled but gave the bearings a chance of survival at the very high rpms that it ran at. It's probably kicking about in a cupboard in the workshop.
vtsteam:
That's pretty cool, Andrew.  :thumbup: What did you cut with it?

That also just reminded me I picked up a little turbine spindle, used at one of the old Bernardston Gas Engine shows. Forgot I had it. It was just a curiosity to me, and cheap. Unfortunately, there's no compressed air in the shed where the cnc router is, so I can't use it. Also it's kinda small.  I don't have much of a compressor in my tiny shop near the house, either.

Right now, I'm working on getting the 500 watt spindle fitted to the CNC. Looks like the router mount fits a 70-71mm body, and my 500 watt spindle has a 52mm body. I think I'll keep the existing mount and just make a 71/52mm adapter.

I was rummaging around in my scrap box and found this big chunk of aluminum, so I don't have to cast anything:

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