Where I first started work there was a Lorch lathe with similar all hard spindle and bearings, now that lathe had a flat leather belt drive and oil cups for spindle lubrication,as the company were instrument makers the oil to lube the bearings was known as poilshing oil ,very similar to three in one oil,if the Shell vitrea oil (around 30 sae) was used to lubricate the spindle the belt came off as the spindle would struggle as the bearing clearance was very small.With an elderly lathe like the Adams I would be very loath to remove the bearings or put it out for grinding as there wlll not be many of todays grinding operators who understand the quality of these precision machines,I would try careful use of an oil stone to remove any imperfections and possibly some lapping with very fine abrasives,I remember our employer telling us apprentices that those Lorch bearings and mandrel were taken to a very high hardness which he described as glass hard,I consider myself very fortunate to have received a very good apprenticeship under his guidance.

I'm with the "high spots" people, I see no need to go overboard if the main journels are good.

The play you have just achieved would actually be less with the hydrodynamic cushioning from the oil, and I think you would try some actual turning now. The lathe is small, and you will be able to make the measurements greater by bending the spindle, which would also be the same with a factory fresh lathe. Keep monitoring the heat build up at max rpm, the headstock should not get above luke warm.

Edited By old mart on 12/06/2023 19:43:56

You say the image shown is not your lathe – it might help to see yours! The problems with these bearings as they wear is that most wear is on the steep taper as it is about a ten times smaller area than the shallow taper. Due to the angles involved, this can allow the wedging action that Michael mentioned, and prevent oil flow. Without seeing your actual bearings I would suggest "Timesaver" lapping compound would be worth trying ( it looks as though the image you have shown is in the process of being treated to honing of some sort)

dave8

Good find, Michael, thanks for sharing! Page 20 is there in my .pdf download (but I haven't checked that all the pages are there…)

Edited By Kiwi Bloke on 13/06/2023 01:51:00

As an aside:

Chapter III offers probably the definitive description of the ‘split chuck’ … and it contains [p65] the tabulation of dimensions that has been copied [without due credit ?] elsewhere.

MichaelG.

Possibly a glitch at your end of the download – it's all present and correct in my copy. (Bloody computers!)

You want to be careful not to take too much off that steep angle thrust face. If you let that spindle move very much at all axially, the long shallow tapered surfaces could come in contact and form a nice driving fit like a Morse taper.

Half to one thou is a good oil gap to start with on the main shallow taper.

Your bearings look to be in pretty good shape. But I would pay special attention to the area where the two tapers meet to be sure there is no binding there – quite often there is a relief cut into the bearing there.

dave8

Edited By david bennett 8 on 13/06/2023 11:12:52

Edited By david bennett 8 on 13/06/2023 11:15:02

Howard, these bearings are normally through-hardened, not case-hardened.

dave8