Super 7 countershaft

I have just finished pulling the old bushes from the casting. Quite a tight fit. The new ones just about wring onto the shaft as they are. I assume that they will get smaller when I press them into the casting. Time for the expanding reamer? Or do I have to lap them?

Maurice, take alook at the work Steve Jordan has covered on You Tube it deals withe the work you are doing. click this link hoping it works https://www.youtube.com/watch?v=u9UuUctxy4k. oops sorry cut and paste.

Regards

Brian

Thanks, will do.

Oilite bushes, due to their porous nature are designed to be at the correct (designated) bore size when fitted into a housing of the prescribed dimension. I would not expect them to be a tight fit on the shaft prior to fitting. If your bushes are anticipated to be under size in the bore when fitted, it will be because the housing dimension is incorrect or the fitting procedure is poor.

If you attempt to ream these bushes in situ, you will 'smear' the honeycomb structure of the oilite and thus close of many of the pores that hold the oil. Thus the self lubricating properties will be compromised.

If the original bushes were oilite then the housing for them should be of the correct dimension. These bushes are actually quite fragile and to obtain the correct clearances you need to be very precise when installing them to ensure that they are accurately located along the axis of the bore, otherwise they will become (perhaps very slightly) distorted as they are inserted.

Thanks for that Swarfmaker. I am now a little concerned. The shaft is exactly to size, and I can just about get the bushes to go on, straight from the packet! Any compression from being inserted into the casting will,I think, make it impossible. They were not expensive, so I am now considering making my own bushes from bronze bar. Fortunately I have access to another lathe.

Swarf Maker is absolutely correct with his advice on Oilite Bushes, the fitting guide in the link below says that a 'm5 fitting pin' should be used on assembly to give the correct bore.

https://www.ondrives.com/data/pdf/bearings/bushings/oilites-tech.pdf

Thanks for that Sandgrounder. This leads to my next question; what is an m5 fitting pin, and how is it used. Also, on the "Ondrives" site there is a paragraph that starts. "Re-oiling. After machining of the bearing......... " What sort of machining are they referring to? If it is sharp, is reaming not machining? I'm struggling here!

An 'm5 fitting pin' would be a bar machined to suit the internal diameter of the oilite bush with British Standard 'm5' tolerance, which according to the website below would for say a 16mm dia bore bush be 16.015 / 16.007, there would also be a shoulder on the bar to press the bush in, this would ensure the the bush ended up with the correct internal diameter, the pin would if used for hand fitting also help to keep the bush in line with the hole.

http://uk.misumi-ec.com/pdf/press/us_12e_pr1263.pdf

but if your replacing needle rollers neither the existing shaft or housing may have the correct tolerances suit a standard oilite bush.

I would think that the 'after machining' refers to either the length or the non running diameter, as Swarf Maker said machining of the running surface will smear the surface and close the pores.

Edited By Sandgrounder on 19/07/2017 19:52:59

Now I understand. Thank you. I think I see my way forward now. Thanks for all the contributions

I recently ( last weekend ) replaced my Ml7 countershaft and fitted oilite bushes , I encountered the same problem as you ,what I did to over come the problem was to sand the countershaft down using 320 grade wet and dry paper on my other lathe.

Once I spent a bit of time polishing the shaft it fitted perfectly ,no play or sloppiness , the pulleys were still a nice fit too ( before anyone makes a comment ) remembering that they located on the shaft via grub screws , I 'spotted ' the shaft where the grub screws would sit ,ensure they won't turn on the countershaft .

That sounds a promising idea. I believe I already have an alloy lap the right size that I could use. It hadn't occur to me until you mentioned it . Thanks.

From the Oilite tech literature:

pores and will not allow the oil to flow freely

For more, see **LINK**

Thanks for that Hopper. that tells me all I need to know. Great!

Maurice

Just a quick update to round things off. I have learned a few things.

(a) Oilite bushes do get smaller when pressed in. With my lathe in bits I couldn't make a pin to keep it to size, and I expect that it should be ground anyway. I did try a piece of ground bar that was a very close fit; it still ended up undersize, and I had a hard time getting it out of the inserted bush.

(b) Yes, Oilite bushes can be reamed as several people and "Oilite " themselves say, as long as the reamer is sharp.

(c) Don't buy an adjustable reamer for fifteen pounds! I did; all the blades are different heights and the rear of the parallel portion had sharp corners proud of the rest of the blades, that dig in. I wish now that I had bought a Dormer one for nearly seventy pounds, as this would have made a set I have complete.

(d) When the bushes are just a nice fit with now shake, when assembled and run, they over heat and start to seize. I took a barely perceptible amount off and it now runs very nicely; even on the higher speed range. My lathe has never been this quiet!

Thanks to all those who responded to my questions. As ever they were a great help.