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Help!! 9c spindle bearing clearances .


Aug 5, 2021
I have been working on my 9C for a wee while since I went to swap out the failing leather belt for a ribbed belt.
I have cleaned up the cast iron bearings and had the spindle cleaned.
Completely stripped the machine and cleaned it.
Fitted new felts.
Bought the correct oil.
Levelled the bed as best I can.
Fitted the thrust bearing at the back of the spindle
I have reassembled it and am having trouble setting my spindle clearances.
Info I have found states .001-.0015 for my model which converts to .0254mm-.0381mm
I am having trouble getting my gap big enough.
I let all bearing clamps go and slacken off the spindle back bearing
I have the back close (I work in metrics) and have been getting it to .020mm and at the chuck end I am just managing to get .017mm.
I am having to force the gap, open to fit shims in
But when I get this I can grab the chuck end and hear and feel vertical and horizontal movement and unless I have the drive belt very tight or lose I get what sounds like bearing chatter from the chuck end bearing.
This chatter sound also happens when the lathe is turned on but is less when run in reverse.
Only the spindle is engaged.
Before I stripped it down the back bearing was always done up tight but the front one when tightened would clamp down on the spindle and not allow movement so I backed it off till it spun freely.
This is an old lathe that dates from the 1940s so it will have its own way of doing things and maybe it has been run for many years without the spindle being setup correctly, maybe the bearings are out of round but everything spins true on the dti.
I didnt mic the bearings to check if round as it never crossed my mind.
I am a bit in the dark as to how to proceed and am asking the experts on this forum so please suggest away as I really like my old girl and want to get running properly again.

A couple of points to consider:

First, in order to really evaluate what you have, you need to accurately measure the spindle diameters and the bearing bores. You have to know if the bearing bores are oblong which will make setting the clearances difficult.

Second, do not run the spindle with bearing bolts loose. That will add a degree of flexibility to the system which you don't want and which will lead to trouble like the chatter you mention.

The fact that the spindle seizes when you tighten down the clamp bolts indicates that the correct shims are not in place and on an old lathe like that, parts tend to go missing over time so it's likely the correct shims have been lost. The fact that you have to pry the bearing open to get shims in is a little puzzling. It's possible that you do not have the original spindle. That's not to say you can't make the system work. Get the bearings shimmed properly so you don't have to run with the clamp bolts loose.
just for ballpark, you might lay in two sheets of copy paper (.006 or so - .15M) and bring the caps to one or two fingers tight. Make front and back the same to a feeler gauge check as a starting point.

Getting close you might put on a little blue and see how it starts to rub.
Rub - about .002 (.05mm) or so.
Thanks for the replies guys.
I have got it nearly sorted and it was none of your excellent suggestions.
It all came to to the idiot let lose with the dti gauge, yes me.
I was reading it wrong and was multiplying everything by 10.
I was pondering this whilst sitting staring at the lathe and I worked this out by putting a feeler gauge under the dti and removing it, yep I was reading the gauge incorrectly.
No doubt I am not the first person and will not be the last person to do this.
Does anyone have the torque setting for the bearing pinch bolt on 9C with cast iron bearings?
I have been running a 6 inch 3 jaw chuck on the lathe and am thinking it might be a bit heavy so will put the 4 inch Taylor chuck it came with on unless I need to turn a bigger diameter. I will strip it down and give a clean.

For anyone tearing down a machine, it is good to measure each shim and each stack carefully and draw a map of sizes and location so you can add or withdraw evenly. Not uncommon to find the front and back are not even, but often best not to change more than what is needed to make size.

A machine that has only one side open with a bearing/spindle in a bore, it is important to know that cast iron will only spring so much and a little more can break the top portion right off a machine. Often the spindle is stuck or held by a belt. or something you have not discovers. A medium whack with a 3-pound hammer with a woodblock set where it will least hurt is one method. A hard whack with a 3 pounder can break stuff.