10EE Bearing contact angle and preload

I have a CVA lathe in the UK, same as a EE but with a gearbox drive and styling like a 60's housing scheme.

I have looked through the references to bearings on this site and have seen 15 angle for 10EE bearings.

The various mfs cats list bearing stiffness for different contact angles. However to summarise:

1) The max rotational speed for any is many times that needed, slightly lower for 25 degree a/c.

2) The radial stiffness of 15 degree is only slightly lower than 25, however:

3) The axial stiffness for 25 is usually at least twice that for 15.

4) The stiffness for all is increased with preload, at the expense of bearing life and max speed, still way above lathe speed.

So it would seem that a heavy preload and 25 degree a/c would be best, any comments?

As an aside, I used to have use of a UK made Bridgeport made by Adcock and Shipley in the UK, which had an extra heavy preload on the spindle bearings. There was a plate on the head saying " Run spindle every day". Could this have been to prevent brinelling of the races? Should we make sure to rotate all preloaded bearings on regular basis?

Many have bought machines that have been unused for years/decades. Does this knacker preloaded bearings?

You have failed to tell us what bearings you are replacing?

If it is the main spindle bearings. From what I understand CVA at some point changed the design and the difficult to procure flanged bearing is not required, just a pair of easily obtainable precision bearings is all you need. No idea what CVA used in the rear.

Sorry mate, the headstock front pair.

As you say, the headstock front pair bearings on CVA are not flanged, Whoopy, still a bit pricey.

Going back to original Q, 15/25 ?

Ps I read your treatise on 10EE bearings, thanks.

Here is a pictures from lathes.co.uk showing a section through the headstock.

http://www.lathes.co.uk/cva/img8.gif

As for the bearing angle. Without looking it up I think 15 degree is the standard for precision bearings unless otherwise specified.

Very responses to this one from a few years back.
I have just started work on this machine.

Thank you from OZ

Did you decide on changing to 25 from 15, or sticking with the latter?

Fafnir differentiated by 2mm was 15 and 3mm was 25

Interesting on the standard preload differences....Size number 10 was 125 lbs for 15 degree and 275 for 25 degree as to "medium" preload

I've done quite a bit of reading about AC bearings when I replaced my milling machine's spindle bearings. One could easily immerse themselves it a lot of material covering the topic for months or years. In the end I didn't fret too much about the contact angle, but that could play into critical applications. My take away was that the preload is super important. Preload could be established at the factory with (IIRC) "universal" AC bearings. In this case the bearing races are ground with a prelaod established at the factory and can be matched (ish) with other similarly processed bearings. The other choice is to not have "matched" or "universal" AC bearings and go through a process which most of us don't have anything near the capability to do and match them in the field. Matching super precise AC bearing in the field involves a process of precisely grinding the inner and outer race spacers to establish the critical preload. So depending what you are up to machine tool AC spindle bearings can be challenging.