Myford S7 countershaft bush temperature

Question for Maurice:

When you reamed your new bushes how did you ensure the two bushes were in line? did you have some kind of pilot on the end of the reamer which spanned the two bushes?

I'm planning this job myself in the not too distant, and I've been puzzling over this.

TIA

Mike

Wonder if thicker oil would change the problem?

Regarding heavier oils, Bromor make oil impregnated bronze bushes that require one to soak them in SAE 100 oil for 12 hours if you have machined the bush.

Bromor state that:

During manufacture the bar stock is vacuum impregnated with oil to a level of some 18 % (by volume).

The oil is supplied to the shaft through thousands of interconnected, oil-impregnated pores.

Due to capillary action present in the material, the shaft is wet with oil, whether in motion or not.

An immediate oil wedge is always present when the shaft is in motion, assuring proper lubrication at all times.

.

For convenient reference, see page 6 of this pdf: **LINK**

http://www.bearing.co.il/OILITE.pdf

MichaelG.

Edited By Michael Gilligan on 01/03/2019 20:42:35

Dennis

In case it’s of interest, and to give you some reference points. I was doing some turning for an hour or so on my S7 this afternoon, mainly around 600 rpm. For my own interest, when I’d finished I ran the lathe up 1500rpm for a couple of minutes, and then to its maximum speed (2150rpm) and let it run for 7 or 8 minutes to see what bearing temperatures I would get. Temperature on the left hand countershaft bearing housing was 30C. Temperature on the rhs was 25C. Headstock bearing housing was 31C. For reference the ambient workshop temperature was 17C. My lathe dates from 1958, and as far as I know it still has the original countershaft and oilite countershaft bearings. There is some play here, certainly rather more than you reported in your lathe, and I do need to top up the oil cups at the start of every session (with ISO32 hydraulic oil). However there is no evidence of oil bubbling out of the oil cups.

Mike .....thank you for this useful feedback. My S7 is running very well on the low speed range with all bushes and bearings at room temperature. On the high speed range only the countershaft bush next to the clutch gets hot when running at the 2 highest speeds.

I am still going to fit new Oilite bushes and will post the outcome.

I'm sorry for the long delay in replying to the question about aligning the bushes to press them in; I have been a bit unwell. Back now!

I first thought that I could leave the right hand bush in situ; pass a length of suitable ground bar through it, and through the vacant left hand hole. I could then slip the new bushes onto the end of the bar, knowing that they were in alignment. However, as soon as they begin to get pressed in, they close up gripping the bar. I might have got away with pressing them in just a short way and then driving the bar out before finishing the pressing operation. I decided not to in the end, as I didn't want to risk damaging the bushes or the bar.

In the end I turned up two thick stepped washers with the reduced diameter a close fit in the bushes, and the larger diameter slightly larger than the O/D of the bushes. The centre hole was made a close fit on a length of studding. I assembled it, from the right, nut, stepped washer inserted in end of RHS bush, thought the LHS of the casting, New bush with the other stepped washer in it, and the final nut. The the LHS of the casting is machined flat for a fibre washer. When the nuts were nipped up it was virtually self aligning. A little jiggling as the nuts were screwed tighter, and the bush entered the bore quite smoothly. On reflection, it would have been better to make the RHS stepped washer, a close fit on the plain part of a suitable length bolt, and long enough to go right through the remaining "Oilite" bush, retaining the larger lip of course. This would have held the new bush a little more accurately .

However, the procedure I describe worked, just reversing the assemble to insert the new bush at the other end. I hope this helps. Sorry again for the delay.

Regards Maurice

Maurice

Hope you’re back in good health.

Thank you for your detailed reply, which is very helpful.

However, I was particularly interested in how you reamed the bushes in line. Did you use a piloted reamer?

I also picked up on your comment about a fibre washer on the LHS of the swing head. I have always wondered about the sideways play of the swing head on my lathe, so I’m now wondering if there should be a packing washer(s) here to take up the play.

Regards

Mike

Hi Mike, as I mentioned earlier, I bought an expanding reamer for this job. I expanded it until it would just about slide into the bushes (the LHS of my countershaft has two bushes side by side. I don,t know if they are all alike) and then carefully expanded it until it bit, then started to ream, try, repeat. I couldn’t think of a practical way to arrange a centre to engage the business end of the reamer. Perhaps I just got lucky, but it worked! There may well be a better way. Good luck.

Maurice

Hi Mike, as I mentioned earlier, I bought an expanding reamer for this job. I expanded it until it would just about slide into the bushes (the LHS of my countershaft has two bushes side by side. I don,t know if they are all alike) and then carefully expanded it until it bit, then started to ream, try, repeat. I couldn’t think of a practical way to arrange a centre to engage the business end of the reamer. Perhaps I just got lucky, but it worked! There may well be a better way. Good luck.

Maurice

Thanks Maurice

I suspect that the factory used some some kind of piloted reamer. I will have to give this some more thought.

Long time ago but same happened to my ML7 before scrapping the thing.

At the end of its life lucky if i got 20 mins before the spindle started slowing and left bush burning up too hot to touch. There was monstrous play but ok at first and always ran it above 1000 rpm and still took an eternity.

Heat is a result of friction so either the clearance is wrong or there's not enough effective lubrication. You could try as an experiment something like EP90 (EP = Extreme Pressure) Gear Oil as used in car gearboxes.

I suspect that the 'factory' just pressed the bushes in and left it at that.

regards Martin

I'm about to replace my S7 countershaft Oilite bushes after making up the appropriate dollies and such. Can anyone please advise the length and od of the L & R bushes A9963 A9964, so I can put some on order and also to save me the strip down and reassembly to measure them?

Many thanks

Peter

No i don't recall the specifics and my lathe is an ML7 so may be slightly different. But basically the ID is the nominal diameter of the countershaft, which can be measured at the part of he shaft that sticks out the end. The length can be measured off the length of the casting they fit into. Mine had two bushings side by side in each casting, with a small gap in the middle for the oil from the oiler to fill up. OD is whatever the standard Oilite dimension for that at ID is. Usually, from memory, about 1/16" wall thickness, so ID plus 1/8".

I reamed mine very lightly with an adjustable reamer set very lightly so the nose of it was entering the next bushing to keep it in line. Before that stage though, I found the swinging H frame the bushes go in was a bit bent out of shape, so I tweaked it back in line by with a long bar of BDMS the same diameter as the counter shaft put through the bushings and used to bend the Mazak H frame back straight again. When all is in line, the bar will slide straight through both bushings in both sides of the H frame.

Edited By Hopper on 18/03/2022 12:10:14

Thanks Hopper. I wasn't aware there are std relationships between wall thickness and OD on Oilites. S7 is quite different to ML7; on the LHS there is a washer, thrust bearing and collar as well as the bushing inside the housing whilst on the RHS there is the cam shaft assy beyond the bushing inside the housing. Guessing bushing length on each side therefore gets tricky.

I've recently had all the clutch, drive pulley and countershaft parts stripped out and inspected in an attempt to solve a vibration problem. The LH Oilite had some wear but not enough in my mind to cause the vibration so I left it alone The RHS seemed pretty good and so moved on to the pulley bearings. They weren't that bad but I renewed them. After reassembly with new Fenner drive belts the vibration problem was nearly solved but still not perfect. At this stage I realised I'd left two riser block hold down nuts slack after some bed set up experiments a couple of months earlier. Great personal embarrassment. Changing the LH Oilite now is simply because the oil cup empties over an afternoon and if I'm making the tooling to do one I might as well do the other.

Since posting this morning I've seen that the S7 countershaft Oilite OD is quoted as 1 1/8" elsewhere in this thread. Taking the clutch/countershaft assy out is not that time consuming however I can't get the 2BA x 1/2" socket countersunk screw securing the clutch cam shaft arm out; working from the front of the lathe, even with freshly squared up Allen keys, so I reckon I'll have to have the swing head out on the bench to work on it. So I'd be very grateful if anybody knows the length of the Oilites!

Peter

I have a pair of new oilit bushes for the S7 in the shed as well as the thrust bearing. They are the last bearings I need to replace, just no time.

Will measure them in the morning. I bought them from Myfords because to purchase locally I needed to purchase 2 longer lengths of oilit which was going to cost almost the same as purchasing from Myfords.

Peter

Thanks for that Peter. It will be useful.

Regards

Peter

The bush dimensions are in the original units, both bushes are the same outside diameter and bore. In Australia I could only find Oilit bushes that were available were too long and expensive, but no long enough to get 2 bushes out of the one length.

OD 1.1/8"
ID 7/8"
Length short is 3/4" Long 1.25"

Peter