[cowanrg]

I'm upgrading my mill to a belt drive and was wondering why everyone only replaces just the quill bearings? I have a PM30, and it's a similar design to the G0704, and people don't seem to bother with the 'drive' bearings, or the ones at the top and bottom of the gear. Is it unnecessary to replace these? Mine has 6211 and 6207, and both say they are limited to ~4500 RPM, but I'm going to doing around 6500. will this cause a problem?

[Fastest1]

If you are using the internal gears it might be of concern. Usually the belt drive goes between the motor and the spindle bypassing the gearing entirely.

[cowanrg]

true, but they are still supporting the spindle assembly. These are the bearings that support the upper gear assembly, and the upper part of the spindle. it's what comes into contact with the spline.

I just did more looking and the bearings are 6211Z and 6207Z. I guess the 'Z' on the end means they can support higher RPM. It looks like 6500 should be just fine.

[Fastest1]

Actually IIRC in Hoss plans. He makes a spacer that eliminated the gears that interface with the spindle, so that middle shaft isn't spinning. Most remove it entirely.

Btw, since you are already in there. Why not use the bearing with the highest rpm and load rating. Just a few dollars difference.

[Wiggles84]

If I understand what you are saying, its the two bearings that on the what I would call the upper quill assembly.

I'm not sure if you have to replace them. I did but that was because I was a dumbass and did some machining on that assembly and left the bearings on there (nuts).

I think I remember having a little heat issue at first buy found out I had to much tension on the belt drive conversion.

@ Fastest

I think what you are referring to is the 3D printed piece that stops the slapping noise between the spindle and quill?

Andrew

[Fastest1]

No I was referring to the large aluminum cylinder spacer between the bearings.

[cowanrg]

I will be removing the intermediate gears, so they won't be in contact with the gears on the spindle. BUT, that section of the spindle still spins, it's where the spline of the spindle/quill assembly meets up with the gears. All those bearings still spin, and the top two still support the spindle to some degree. so, they need to be rated for the RPMs.

I looked for higher RPM versions and they don't exist, at least not cheaply. I'm sticking with what's in there because they appear to be rated for 6500 RPM.

I guess you could remove that whole assembly, but it doesn't seem like a great idea since the spindle would be completely unsupported up top and would have the belt pulling it in. It still needs at least one bearing up top for support.

[Wiggles84]

I will be removing the intermediate gears, so they won't be in contact with the gears on the spindle. BUT, that section of the spindle still spins, it's where the spline of the spindle/quill assembly meets up with the gears. All those bearings still spin, and the top two still support the spindle to some degree. so, they need to be rated for the RPMs.

I looked for higher RPM versions and they don't exist, at least not cheaply. I'm sticking with what's in there because they appear to be rated for 6500 RPM.

I guess you could remove that whole assembly, but it doesn't seem like a great idea since the spindle would be completely unsupported up top and would have the belt pulling it in. It still needs at least one bearing up top for support.

Ok, so we are on the same page.

I was also not able to find replacement bearings for higher RPM's. If the need comes for higher RPM bearings I may make some kind of spacer and use a smaller OD bearing.

I too would not run without this on the machine. Would be no support on the upper part of the spindle.

No clue what Fastest1 is referring to? Pics or link?

Andrew