LH countershaft bearing getting v.hot on S7

I understood the bush was loose and running hot, then loctited in,? Agree it will not help oiling.

Well there's a hole in the bush where the oil cup feed is so the oil is getting to the inside surface... I've always got the old one to go back to but this was getting hot also. It was all scarfed up inside so I thought that was the reason - having investigated these things further I guess this was actually someone else's attempt at grooving to spread the oil (see pdf link earlier). Maybe it never needed replacing..... I am inclined to think it is mechanical after everyone's feedback. It is hopefully just a matter of finding out what.

This is certainly an interesting journey of discovery

Thomas,

From memory [which may, of course,be failing] ... Oilite [porous] bronze bushes should not be drilled at the oiler location; they are designed to "wick" the oil throughout the body of the bush. Drilling the bush is counterproductive, and may well be the cause of the original failure.

[sorry if this has been covered already; I have only just skimmed through the discussion]

MichaelG.

Thomas,

First off, If you have received an oilite bush from new Myford that was not a push fit on the outside, then I would say ask new Myford for one that does, FOC.

From reading the above:

1. How long does the oil in the feed cup last before you have to replenish it? Does the new bush appear to leak oil? A new bush on a sound shaft should not spray oil around, and last all day. It should not leak out when the machine is not in use.

2. When you get this heat, can you stop the machine, release the belts and turn the countershaft by hand, or is it then stiff?

3. Is the primary belt pulley wheel on the countershaft warm as well? Do you only get this effect when the mandrel is turning or is it there when the clutch is disengaged? This questions group leads to the pulley bearing nearest to the bush being the real source of your troubles.

Dennis

Hello All,

Sooooo, I went about re-assembling everything back tonight. Loosened the motor and re-alinged it with the pulleys and made sure it was in a comfortable position for the belt, as per a lot of your recommendations. Took the bush out of the oil can and fitted it to the casting - it moved longitudinally very easily but did not rotate so, for its purpose it stays in place pretty well. Plenty of oil and I moved it so the drill hole was a half cresent on the oil hole so it could wick also. Fitted the countershaft pulley and belt etc (was a bit of a pig when the bush could move along with it but managed it in the end).

Ran the lathe at top speed for approx 10-15 mins and the housing was warm. I am pretty happy as before it was getting hot quickly rather than reaching a medium temp and staying there.

I have a feeling running the countershaft without the pulley and belt to the spindle in the equation may have been giving misleading results as it wouldn't have had a counterforce on the opposite side of the bush to balance it, just a thought.

Dennis - I know it is definately the bush that was the source of the heat. I will look out for any tell tale signs you said in points 1 and 2.

Thank you for everybody's input and discussion. All very valuable and I have definately learnt a thing or two.

(Regarding the dodgy clutch cam, after re-assembling the follower in the correct orientation it seems to be behaving itself, if not a bit wobbly when not engaged. Thanks to everyone who answered on that too, when I first started this hobby about 3 years ago I was told you can ask ten different model engineers the same question and you will get ten different answers and all tof them will be correct, this is definately true here, )

Thomas

tom,

i think you might as well make up a brass or gunmetal bush easy fit on shaft and loctite into the housing with oil way.

my own personal view is that i always understood oilite bushes didnt need oil added as formed of a graphite sintered bronze composition.

cheers,

julian

.

Julian,

It's worth reading this Wikipedia page.

MichaelG.

.

P.S.   ... The need [or not] for periodic addition of oil depends on how much oil is "consumed". and this in turn depends upon how generously the bearing was specified for its application. 

Edited By Michael Gilligan on 05/11/2014 07:44:43

Just a thought- try a good dab of Moly-grease on the shaft, can work wonders, takes a few minutes to work.

The bush must NEVER have Loctite anywhere near it, it is now just a plain bronze bush. The bush should be at least .002" interference fit. With the oil around the bearing, the Loctite will not be holding on too much.

Ian S C

Gordon

My only concern with adding a dab of MS grease to the shaft is that it may clog the pores of the oilite bearing. That said it is recommended, see the link in my previous post, that molybdenum disulphide is added to the bearing oil under certain conditioons, see extract here:-

"Standard Oilite® bearings are impregnated with a highly refined mineral oil to ISO VG (SAE 30) having a high viscosity index and containing anti-oxidant, anti-rust and defoamant additives.

To prevent possible seizures with stainless steel, hard-chromium and nickel plated shafts, an addition of molybdenum disulphide to the impregnation oil must be specified."

That said if the grease mixed with the oil then it might work, maybe worth a shot with with the old bearing.

Cheers

Martin

PS I have no idea what has happened to the background on this post, something with the copy command and source material I suspect

Edited By Martin W on 05/11/2014 10:36:53

[Martin and Gordon]

Molybdenum Disuphide additive in the oil should be no problem, because of the minute particle size; but I would think the grease likely to clog the pores and reduce the capilliary oil wicking.

If no additive is to-hand, then maybe pre-mix some Moly Grease and light oil ?

MichaelG.

I take the point that grease can clog the pores. My moly grease is pretty old and quite thin, just about sticks to the shaft. I often use moly ( after running in ) then ,after a few hours running, revert to oil. The idea is that the bearing surface gets plated with a very thin layer of moly. I remember that it was not recommended for roller bearings or synchro. gearboxes because it was so good! I would just make a brass bush for the c/shaft or refit with cheapo ball races.

Little bearing tale :-

My Brother in law bought a cheap battery powered cylinder mower last summer. Apparently it never worked that well, he used it 5 times and put it away. He has replaced with a different one, so I got it for free .
Major problem was that an intermediate idler gear(phos bronze lined) was just about seized on a fixed steel shaft. It looked as though it was greased, sort of black goo around it, problem it was not grease as we know it Jim! It was a black dust which more or less dissolved in thin oil, but the shaft had a permanent black colouration on it. Re-greasing the shaft and idler bore with LM grease gave a nice running feel. So what was the mysterious substance, can't have been grease its only 8 months old!

post script:- After about 10 hours, use I decided that the blades needed sorting, so I stripped it again. Would you believe it, my LM was just about shot, there was a definite drag on the idler when spun, so I cleaned and re-greased it. Funny how LM works in car wheel bearings for 100,000 miles, but dries out in a puny lawn mower in months. I wonder if the bearing is "sucking" the oily bit out of the grease.

Frank