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Spindle bearing woes

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Izzy

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#1
So about a year ago I bought and restored an old McKenzie lathe which the group was great for helping me with the questions I had. At the time I didn't do much with the spindle bearings other than set the oil clearance with shims and plasti-gage. The lathe ran great for the last year and I've made alot of parts with it since I've had it running but just recently I've been getting chatter and it's been getting worse and worse to the point where today I measured .015" play at the end of a 6" part. The chatter was too much I had to do something About it so I tore into it did some investigating. I measured .004" play at the spindle at both the front and back bearings. I also took the spindle out to get a look at things and measure. The spindle measured nice an round everywhere I measured. The bearings not so much... they're pretty scored along with the spindle and the bearings are measurably egg shaped. :( The 2 numbers for the bearings where taken 90° apart, I took a few more measurements that aren't written down. All the measurements are in the pictures Along with pictures of the bearings and spindle itself. What do you guys recommend be the course of action? The bearings where measure with no shims installed and bolts tightened down. IMG_20180926_181630.jpg IMG_20180926_181649.jpg IMG_20180926_181709.jpg IMG_20180926_181731.jpg IMG_20180926_181807.jpg IMG_20180926_181829.jpg IMG_20180926_181950.jpg IMG_20180926_182011.jpg IMG_20180927_010402.jpg
 

Izzy

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#2
I don't know if I'm going about this the right way but I need the machine back up and running and with no advice yet I went out on a whim and stoned and polished up a bearing cap to see where that would get me. Here's what it looks like. Still unsure if I should even be doing this someone out there has got to have a light to shine on this. IMG_20180928_122413.jpg
 

Izzy

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#3
I had the idea to get some Prussian blue and marking the bearing to the spindle I just don't know if this would be a good idea or not. There's definitely material that can be taken off the spindle doesn't move at all without shims under the caps. Is it possible to scrape them in new like that?
 

pontiac428

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#4
The usual treatment for a saddle bearing is to skim (grind) a tiny amount of material off the cap where the two mating pieces contact (along the "saw line" of the bushing), and then hone the bearing to size. It will never be perfectly round, but you can get real close. If I were to go that route, I would grind the spindle smooth on the bearing contact surfaces, measure it, then grind the cap and torque into place. Then I would use a hone (if compatible with the bearing material) and hone out the bearing to match the spindle plus an oil clearance. That's probably the best one can do short of taking the whole project to a better quipped shop. Edit: if you can separate the bearing from the saddle and cap, you can do the work on a lathe.
 

Izzy

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#5
This is the exact kinda advice I was looking for I didn't know that was an option. Unfortunately I'm just a home gamer and this is my only lathe. The chatter was getting so bad I had to tear it apart to do something! I the only other machine I have is my Bridgeport. I don't mind brining the head stock and bearings and spindle to a shop and having them do the work but if there's anything I can do to minimize the cost or if I can do something with the Bridgeport? The headstock comes right off this old lathe...
 

Izzy

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#6
IMG_20180928_130306.jpg
She's pretty simple
 

pontiac428

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#7
Oh, I didn't realize the headstock was easy to remove. An automotive machine shop should be able to do the job for you for a price that won't give you stomach cramps. I'd hit the yellow pages and ask around, that should be an easy job to get done.
 

Izzy

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#8
@pontiac428 well that puts me a little more at ease, thank you! So there's nothing that could be done by my hands either on the Bridgeport or with a little elbow grease? If not I'll call around. There's only 2 automotive machine shops in town.
 

BaronJ

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#9
Hi Izzy,

You said the spindle binds up solid when you take the shims out.

Use a pair of feeler gauges on either side of the bearing cap to get an idea of how thick the shims need to be.
Make quite sure that they go back on the right way round, the way they came off.
The technique is this rub the saddle and bearing on some abrasive paper, just to make sure the mating surfaces are clean.
Re-assemble the cap and add shims (feeler gauge) until you have the clearance you want.
If necessary get or make some shims of the right thickness. 5 thou brass or steel shim material is quite common.
I wouldn't do anything to the shaft bearing surfaces unless they were really bad, and looking at your pictures they aren't too bad at all.
If anything I would say those bearings have been oil starved at some point.
 

Izzy

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#10
@BaronJ if you look at my measurements for the spindle its got a high spot in the middle of the front bearing surface and I feel like this should be addressed while I have the spindle out. It's hard to see in the pictures but the spindle is pretty badly scored as well, my finger nail catches everywhere on it. I thought of maybe polishing it up with some Emery cloth using the shoe string method. I think I would have issues trying to set oil clearance when the bearings and the shaft aren't quite round, it would be easy to get false measurements.
 

BaronJ

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#11
Hi Izzy,

I don't see a 3 thou high spot as an issue. You will get that anyway because that is where the oil feed is.
 

Izzy

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#12
So you say I shouldn't try to polish out that 3thou? Or the rest of the bearing surface to smooth it out? Just sand the bearing smooth and hone it to size? I could shave a bit off the caps as suggested by @pontiac428 with my Bridgeport.
 

Izzy

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#13
It could be nothing but the bearings being so out of round and tapered like they are worries me. Also Due to the thrust face wearing out the high spot on the spindle doesn't spin in the center of the bearing anymore it's pushed back by about a 1/16.
 

BaronJ

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#14
Izzy, The 3 thou is nothing ! Don't even bother about it.

As far as shaving anything off the caps or bearing for that matter isn't going to improve things. You have already said that the spindle binds up when you remove the shims ! In that case you need to add shims in order to reduce the effects of any wear.

Assuming your measurements are accurate the variation that you see in the caps is because they probably were not tightened down evenly. Again the few thou difference could quite easily be due to the bearing cap being slightly twisted when fitted. They are not doweled so there is no saying that when you replace them, that they won't end up being in a slightly different place.

I wouldn't worry about the bearings being slightly out of round ! They will never be truly round. Worn thrust faces are another thing altogether.
You may need to make bronze thrust washers to sort that.

But lets do one thing at once.
 

BaronJ

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#15
Izzy, Its my bedtime now ! We can follow up later.
 

Izzy

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#16
@BaronJ thanks I appreciate the help so far! The lathe was restored about a year ago I did it myself and at the time nothing was done to the bearings other than shimming them to get proper oil clearance. I torqued the caps down myself so I know they where done evenly as I used a torque wrench. I measured the step for the bearing cap it seems like the cap itself is what's tapered not the bearing. Looks like this problem is unraveling itself... IMG_20180928_173104.jpg IMG_20180928_173136.jpg
 

Izzy

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#17
My thoughts with the spindle binding up without the shims was that I could remove the shims and take out the extra material that causes it to bind. I just need to have this back up and running a bit longer. Then when the time comes, do as Pontiac said and have a shop skim the caps and line bore it back to size.
 

BaronJ

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#18
Hi Izzy,

You need to think very carefully about this, once you remove material, thats it, you cannot replace it !

When the lathe was made originally, the bearings and caps were deliberately made with shims, not because they were cut wrongly, but because things wear. The shims are there so that the spindle clearances can be adjusted to account for the inevitable wear that will take place over time.
The shims are usually, but not always, a stack of very thin ones, often only a thou or so thick, they can seem like one solid shim because they are compressed by the cap and tend to bond together.

The normal way to adjust the bearings is to remove one or two shims at a time, measuring the spindle rotation as you go.
When the spindle becomes more than hand tight, put one shim back, and check again. It is not a quick process ! I've seen engineers take days to shim shaft bearings. This is why I suggested feeler gauges earlier, in case the shim was solid and not a stack. Even compressing out the surface oil between the shims will affect the clearance.

Whilst I think about it ! Carefully clean the oil drain hole in the bottom bearing. The oil must have somewhere to drain. Remember any dirt that gets into that top oil cup will get into the bearing and cause the scoring that you talk about on the shaft, and lack of oil is even worse because particles of the bearing itself will cause scoring.

When you put it all back together use plenty of clean oil, 10 or 20 SAE motor oil is perfectly fine. If perchance you use multigrade, oil, do not mix it or allow it to mix with detergent oils. It will turn into a paste that won't lubricate anything.

I'll come back later and discuss thrust washers with you.
 

Izzy

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#19
Yes I understand about the shims being there to take up wear over time. This is why I measured without the shims because at that point you've used up all your adjustment and need a more permanent fix per say. The thrust washer I can remake myself once he bearings are good enough I can use the lathe again. I would one day like to do a "real" restoration and get the bearings done properly. I really like this machine and I feel like if I had the bearings done properly the machine would cut much better and last another 100 years. I tried honing the bearings yesterday and i managed to remove alot of the scoring without affecting hole size too much.
I've been using iso32 hydraulic oil on the bearings.
 

Izzy

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#20
Also that isn't an oil drain hole, I thought the same thing but that's actually a pin I can only image to prevent the bearing from spinning. Oil simple runs out the sides of the bearings and honestly it runs through oil like crazy which is just one more reason I want to get this bearing situation all sorted out
 

BaronJ

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#21
Hi Izzy,

Yes a lot of lathes use a total loss lubrication system. My Myford is the same, oil comes out all over the place, the chip tray is swimming in the stuff.

I can't offer anything further. Good luck with your repairs.
 

Izzy

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#22
Well I spent most of the day trying different shims out in different spots. The front bearing has no shim at all now and the back bearing has about .015 in shims left. I got the side to side play down to 2.5 thou and the up and down play to a half thou or less but unfortunately the bearings and shaft are so badly worn that I can't get it any better than that. I'm afraid I'm going to have to get the caps skimmed and the bearings line bored as previously suggested :(
 

Izzy

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#23
Here's how the bearings and shaft turned out after some light polishing and honing. I put the shims between the cap headstock is that correct or should it be between the bearing halves themselves? Seems like alot of the oil is coming out from the split in the bearings. IMG_20180929_144104.jpg IMG_20180929_144123.jpg IMG_20180929_144225.jpg IMG_20180929_144246.jpg IMG_20180929_164344.jpg
 

pontiac428

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#24
The shims go between the saddle and cap. What's going on in that last photo? Is that a shim? If it is, I'd make sure to have crazy glue and plenty of sterile suture and gauze really close by. It might be in backwards.

(from mobile)
 

BaronJ

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#25
Hi Izzy,

Now that you have removed material from both the spindle and the bearings, you are going to have to get the cap and maybe the bearing mating surfaces machined to get back the clearance adjustment ! No shims means that you have got to the limit of how tight you can now get the fit.

I would suggest that 10 thou off the cap faces and a few thou off the bearing might get you back to a sane state. Then add shims in 1 thou steps from 10 down.

The oil escaping from between the bearing split faces is because of the inevitable gap there.
 

Izzy

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#26
@pontiac428 i had pulled the shims out to show where i was putting them. im no machine rebuilder by anymeans i just do this as a hobby so i wanted to make sure im doing things right. on a side note im assuming saddle=headstock? just to make sure we're on the same page here.
@BaronJ the front bearing spun without shims before i did any honing or polishing its the back bearing that would bind up without any shims. im afraid im going to have to get the caps skimmed and line bored as both you and pontiac have suggested i just need to finish this part before sending my lathe off for repairs. do you reckon i could save a bit of money and skim the caps myself on the bridgeport then just have someone line bore the bearings and grind the shaft?
 

Bob Korves

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#27
Also note that as the spindle moves up or down in relation to the headstock, it also moves in relation to the tailstock. The tailstock center may end up too high and need work also.
 

Izzy

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#28
yea im not looking forward to the tailstock adjustment after doing all this but the spindle is #1 priority. assuming i get the caps skimmed and the bearing re-bored ill probably have to lower the tailstock correct? how would i even go about doing that?
 

BaronJ

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#29
Hi Izzy, Guys,

OK Izzy, do it the hard way !

Use some 600-800 grit emery paper on a good flat surface, like a piece of plate glass. Stick the emery paper down with double sided tape at the top and bottom edges. Use oil to act as a lubricant between the work and emery paper. All the oil is intended to do is to stop the emery paper surface from clogging up. The oil will contain most if not all the material removed. You must clean the caps/bearings thoroughly before testing. The thing you don't want is transferring abrasive particles to the lathe spindle.

Rub the bearing cap on the emery paper, wipe it clean test with the bearing in place, and do it again, until you have a fit that you are happy with.
Do the front cap and bearing first. Leave the rear cap off until you have done the front one.

Then leave the front cap off until you have set the rear one.

At this point you will have a known set of shims for both front and back bearings. Now you can start to set the spindle clearances as you want them.
Either adding shims or rubbing off material from the caps.

The headstock is the part you are working on ! The saddle is the part that moves up and down the lathe bed.
 

pontiac428

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#30
When I spoke of the saddle and cap, I was referring to the two halves that enclose the bearing. The portion webbed into the headstock is the saddle, and the bearing cap is the cap. A lathe has its own saddle/carrier, but the conversation was about bearings so I didn't think clarification is necessary. Sorry for muddying the waters.

Sent from my HTC U11 using Tapatalk
 
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