empire lathe

morning all swarf makers

ive got a empire lathe needs some love how difficult if possible to change head stock taper bronze bearings to taper roller bearings

Are you sure they are tapered? Most were a parallel split bronze bearing that can be scraped to fit the shaft, and the half-shell joining surfaces shimmed or filed to get correct clearance.

Either way, changing to taper rollers, if there is enough metal to accommodate them in the casting, requires very careful set up in a milling machine or line borer to bore out the bearing recesses to fit the taper roller races and to provide the necessary shoulder to tighten them up against to set preload. How accurately this is done determines how much work will need doing on reassembly to align the headstock spindle with the lathe bed ways. Some scraping and or shimming of the headstock base may be required. Not a beginner's project to be sure.

From the Tony Griffiths site , they appear to have a slight taper on the MKI lathe the MKII had timken roller bearings and a more robust headstock..

Edited By mark smith 20 on 03/09/2017 10:35:33

As Marks pictures show if your Empire lathe is the same as the one here :- **LINK** there is not enough metal in the plain bearing headstock to fit taper rollers. In such sizes taper roller bearing OD will probably be approaching 2" greater than the bore size.  Were it that easy the makers would not have produced an entirely new headstock for the taper bearing version.

If you really want to change to anti-friction rolling element bearings, adjustable plain bearings are quite thick so there might be room for a needle roller assembly. SKF and other brands do high quality combined needle roller and ball thrust bearing units that should more than adequate for home workshop level lathe uses. Probably wise to be sitting down with glass of suitable restorative to hand before asking the price tho'.

In a practical world a step too far given that the Empire was made as modestly priced, modestly specified but none the less effective machine of its era.

Clive.

Edited By Clive Foster on 03/09/2017 11:01:31

Well, if they are tapered bronze bearings, is it possible to adjust them to take up slack and carry on? Or have they been destroyed completely?

My old Drummond has tapered OD bronze bearings,which at some point in the distant past, have been bored out and whitemetal poured in place and machined/scraped to fit, as was standard practice on many machines including automotive main bearings in the early 20C. Might be a possibility to salvage your existing bearings if beyond repair?

Yup, white metal. They used it in 100 ton locomotive bearings, tuff stuff.

Our Ruston Hornsby 6 HR single cylinder horizontal oil engine (26hp) has a white metal big end bearing. The engine is only used infrequently for short demonstration runs, When it was rebuilt about 23 years ago the bearing was remetaled, about 5 yrs ago the bearing failed, probably no more than 50 hrs run time, fingers crossed this time.

Ian S C

Our Ruston Hornsby 6 HR single cylinder horizontal oil engine (26hp) has a white metal big end bearing

While metal bearings can have very different analyses. Diesels generally get a much harder grade (more tin and less lead, along with other minor constituents). 200 tonnes running on only two white metal bearings is not uncommon.

White metalled big ends are ubiquitous in cars and normally good for 250,000 miles with superfinished journals and decent oil...

Neil

Steel backed, (thinwall) bearings are very durable, when fed with a copious supply of clean oil.

The oil flow is important because it is there to cool the bearing, as well as to lubricate, so clearance is important.

Current materials used in engines tend to be Aluminium/Tin, or Aluminium/Silicon.

Thick wall (metalled in place) bearings mostly found in pre WW2 engines, lacking the support of the steel backing, tend to be less capable of withstanding high loads.

In either case, the surface finish of the journal is important. A bearing that will run for ages on a shaft with a 16 microinch Centre Line Average shaft will show signs of wear on 18 CLA and fail prematurely on 20 CLA.

Thinwall bearings are usually broached. A bored bearing has be VERY finely bored, (akin to, or better than the shaft). Under the pressures seen locally, a 0.00001" groove can produce failure in a heavily loaded bearing, since it acts a drain groove for the oil!

The limit is the product of rubbing speed and pressure. Hence a steadily rotating arrangement will stand a high load at low speed. Bearings for reciprocating engines are more heavily loaded because they have to withstand the loads involved in bringing the reciprocating masses to a halt, and then accelerating them in the opposite direction at the end of each stroke. Increasing the speed can turn a reliable engine in to a bearing wrecker, because the inertia loads relate to the square of the speed.

(A friend of mine with a Ruston HR1, and would be interested to find spares for the Injector, or a complete working unit).

Howard