When I was at the point of buying a BH600, Roger Warren strongly advised against disturbing the bearings and oil seals, but to replace the belt (B Section I think ) with link belting, such as Nu Twist, when the need arose.

This would be an easier and quicker, and probably less messy, method rather than having to reset the preload on the bearings, and, most probably, replace the oil seals.

My BL12-24 (A clone of the BH600 / Chester Craftsman ) still has its original belts in quite good condition after some 17 years, if that is any guide.

If the problem is that the secondary belt, to the Mandrel is slipping, you can increase the tension by adjusting the length of the link inside the Headstock, that goes over centre to apply tension.

You remove the bolt through the eye of the adjusting link, and screw the eye into or out of the link. I would suggest 1/2 turn at a time until the required tension is obtained.

I thought that my primary belt was slipping. In fact the problem was that the dimple in the inner end of the shaft carrying the lever was not deep enough. Removing the lever and shaft, and deepening the drilling allowed the grubscrew to engage fully, and reassembly led to no more secondary belt slip!

Really, I have slightly overtensioned the belt, since it takes quite a push to put the lever over centre. Being lazy, I found re engaging the bolt through the lower end of the link was a bit a struggle, so rather than adjusting the link by 1/2 a turn, I have lived with it.. Apparently without ill effects, for the last 4 years or so.

HTH

Howard

Have to admit that I have never checked my belts for numbers.

Mine also has a VFD, so because of the motor size /position only one sheave of the primary drive pulleys is used.

But if the seals are leaking, they need to be replaced The new seal lips should not run the same place as the originals, though. they ought to be at least 1.5 mm away If it needs saying protect the seal lips from damage when fitting the Mandrel, by wrapping any sharp edges / threads in masking tape. with oil on the areas where the seals are going to run, so that the start up is not dry.

Setting the pre;load on the bearings needs to be done carefully. Taper rollers don't live long if over loaded, but you cannot afford to have any slop or accuracy, at least, suffers. It would be nice to have instructions on how to do this!

I think that Ketan recommended 0..002" – 0,004" for mini lathe bearings. I would hope that 0.002" would ensure accuracy without shortening bearing life. My method would be a gentle initial set up, followed by about ten minutes running to settle every thing in and then back off to set the final preload.

Good luck, hope it goes well.

Howard