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Hi I’m new here I was on MyFord lathes and had put up a new post about new ml7 lathe spindles for sale complete with the new bearings I thought that were a bargain anyway there was a guy who posted there and said he recommended going with the speed spindle mentioned in this magazine now might seem like a good idea it’s in volumes 209,210,211 if anyone would be so kind to share these articles with me I would really appreciate it

Thanks All in advance for reading

Mark,

Are these new spindles to run in new white metal bearings?

If so, a realistic top speed for that combination, from memory, is something in the order of 600 rpm. The lathe will tolerate brief runs above that speed but for a good life from the bearings that should be regarded is a working limit.

Regards

Brian

We are advised that white metal bearings in a Myford will 'tolerate' a bit over 600 rpm, with its drip-feed oilers.

Old car engines with similar oiling systems (a bit more oil mist, but dirty oil) will stand up to 4000 rpm and much higher out-of-balance loads. And much longer periods of continuous loads.

So - could we push our Myfords round rather more quickly?

Regards, Tim

The articles are about converting to taper roller bearings

With all due respect, Clive, can you quote examples?

The old Fordson Standard provided maximum power @1200rpm (a non-pressurised oiling arrangement). I know of some engines with pumped ‘splash’ crank bearings running up to 2200rpm with aluminium pistons (1600rpm was generally regarded as enough with cast iron pistons). All higher speed engines I have come across have had pressure-fed crankshaft bearings.

All the engines with dippers for crank lubrication were much lower-speed designs (800rpm and below?).

Memory may be failing a bit, but I recall the Honda G42 engine used a dipper/splash system and ran reliably from idle up to bursts of at least 2500 rpm for twelve hours a day, seven days a week for a six/seven month season on leisure go-karts I used to work with.

Just found this which quotes an even higher RPM of 4000!

Links to https://www.engine-specs.net/honda/g42.html

Rob

Was that engine fitted with plain bearings? Many Honda engines have/had roller bearings.

The op asked about myford ML7 and Jason has pointed out this was a taper roller bearing conversion. One could safely go above the makers speed ratings with roller bearings. I take tit was in MEW ? Noel.

Yes those are the MEW issue numbers in the opening post

Good point! I can't remember, to be honest - I still have one in the shed somewhere so might have a look one day (it's earmarked for a generator project).

You are probably correct about the roller bearings

Rob

Drip, or splash fed plain bearings are limited in speed because of temperature factors, as well as rubbing speeds or load.

Pressure fed bearings are better at building up a "wedge" of oil, for hydrodynamic lubrication, but the increased flow is to cool the bearing. Hence, pressure fed bearings tend to run with larger clearances, to encourage a flow to cool the bearing.

On main propulsion engines on ships, bearing temperatures are monitored, rather than oil pressure.

Excessive oil temperatures degrade the oil, not that a lathe should produce localised temperatures in excess of 110C.

Over heating white metal bearings cause the composition of the bearing alloy to change, (not for the better! ) some time before they fail. Sometimes, the constituents start to separate out.

For really high speeds, such as automotive turbochargers the bearing are actually sleeve bearings where the sleeve is white metal coated on both internal and external faces. In this way, the sleeve rotates and the rubbing speed relative to the shaft and to the housing is decreased.

Howard