Safe Spindle Temperature?

[suntravel]

Usually no grease but deep freezing, so it slips in easy.

Uwe

[RJS100]

Thanks you!

[RJS100]

Ok, I successfully installed the new SKF tapered roller bearings. I have one question regarding preload.

I slowly tightened the spindle nut until all endplay was removed. I measured this endplay by placing a magnetic base on the quill/spindle body and the dial test indicator on the spindle nose. In a similar fashion, I then measured the runout in the spindle. It was immeasurable with using my 0.0005 dial test indicator!!

I then ran the spindle for 30 minutes at increasing rpms and compared the temperature to the OEM NTN taper roller bearings. The spindle was not loaded at this time. Please see below.

I am bit concerned. With the OEM bearings, at 4500 rpm it was running 175F. With the new bearings I am running only 93F at 5000 rpms. Several other hobbyists that have the exact same machine with these SKF bearings report a steady temp of about 180F under load at 6000 rpm. SKF says that an operating temp of up to 225F is fine.

Do my lower temperature readings mean I do not have enough preload? When adjusting preload, should I have continued tightening a bit further after the point that all endplay was removed?

I did expect my temps to possibly be about 30 degrees less since I am temporarily using an oversized oil seal to rule out issues associated with a tight oil seal, but my temps are as 84F degrees lower at 4500 rpm.

Thanks... Richard

[RJS100]

Ok... I did one more test. I found a 3/4" one foot long steel rod and installed it directly into the R8 Collet (see below). I pushed and pulled radially and found far less than .005 run out. I also pulled on it axially up and down to check for endplay. Still immeasurable.

I am still unclear on the topic of preload. My understanding is that these tapered roller bearings (like angular contact bearings) are designed to work in pairs. In this scenario, they are designed to have an axial force pressing the bearings together. I believe the ring geometry is such that they act as springs that get compressed by the axial preload. If this is correct, then adjusting the spindle nut just to the point that there is no endplay, would not compress the ring geometry and therefore result in no preload.

Does this make any sense?

Thanks… Richard