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Help re: adjusting vintage lathe spindle bushes

Costa

Plastic
Joined
Nov 28, 2012
Location
Australia
Hi everyone,
I'm new to this forum and new to lathe ownership! I've bought a vintage lathe - probably English or Australian, no identification on it. It's a typical unit with power feed, a back gear, leather drive belt to a pulley system above it hanging on a big bracket. The wear isn't as bad as I thought it would be, and most of the problems with it seem to be due to mechanically unsympathetic owners rather than a great deal of use, which is typical I guess.
I pulled the spindle apart as the worm screw that engages or disengages the pulleys from the spindle when using the back gear had fallen into the pulleys (and I found another worm screw that had fallen in at some time in the past!), and gave it all a clean and put it back together. The problem is I can't seem to adjust the bushes without them either being too loose or binding.
It has tapered bushes, not too badly worn (although the headstock end oil hole was blocked and there was evidence of overheating - the bush might even have spun, I had to re-drill the oil hole.
It's a weird system for tensioning. There's two circular lock nuts for taking up the slack, the shaft finished with a depression where sits a ball bearing, pushed on by another threaded shaft with it's own lock ring on an outrigger support. I hope that makes sense! Every time I take the slack out it binds. If I leave slack it loosens up further... There is no play in the bushes that I can feel.
It looks like you preload the shaft with the little shaft on the back via the ball bearing to keep a bit of clearance before you lock the main shaft itself - does that make sense? Any advice would be greatly appreciated.
Thanks.
 
Pics

Here are some pics, as requested, sorry they're a little blurry, used an old camera which was already in the shed. You can see the tapered bushes, a shot of the spindle and corresponding tapers, another shot showing the outrigger with the ball all dismantled, and the whole assembly, which is currently working a lot better than when i picked it up a few days ago.
It's very touchy to adjust, it comes loose or binds, though at the moment it's kind of ok. I will replace the two lockrings with something a little more elegant and easy to adjust, they've been butchered. It would be great if anyone could tell me the correct sequence for tightening. Hope the pics are clear enough. Thanks in advance.

https://www.dropbox.com/sh/eitfbug3qjuckh5/LfTUT0CIzr
 
Journal bearings run with a definite clearance, about .001"-.002" (.025-.05 mm) in that size. The oil is pulled around the bearing by boundary layer attachment to the shaft until it forms an almost uniform layer all around, centering the shaft in the bushing. If you have a shaft exactly centered in the chuck and put the point of an indicator on the top, it will rise when you turn the shaft and fall back down .001" or so as the oil squeezes out of the gap at the bottom when you stop. It can be annoying when indicating a part in. You have to turn a bit, then wait while it settles to read the indicator.

Oil the bearings every time you start in the morning, then turn a few times by hand before starting the motor. Properly used journal bearings only touch the shaft when at rest and with care are practically immortal. My 14 1/2" South Bend lathe has the same bearings it came with about 1967 because it was used by a tool & die maker who knew what he was doing and gave me a lecture when I started running it. Part of my new employee orientation speech is that if he is in a hurry to get fired and doesn't want to wait for the usual rituals, let me see him start the lathe without checking the oil cups. I have always used Mobil DTE 24 oil and am quite happy with it.

Bill
 
The spindle must have a shim on the thrust collar at the chuck end of the spindle to control the bearing clearance. There may be on there already. You can determine the thickness of the shim required as follows: With the bearings clean and dry, remove the shim if there is one, push the spindle in hand tight. It will probably bind. Measure the clearance between the thrust collar and the bearing. Make a shim about 4 to 6 thousandths thicker than this measurement. When assembling the end clearance is adjusted by the ring nuts at the left end of the spindle.
Yes, always add oil before starting the machine. ATF is also a good choice for this bearing.
Hugh
 
Your lathe is different in some design features, but nothing totally unusual. Tapered journals in bronze bushes were commonly used.

Here is how I'd approach the matter of setting up your headstock:

1. clean the bronze bushes with solvent and wipe with something like paper shop wipes. Inspect using a good light, looking for burrs or scoring (grooves or gouges). My test is to run my fingernail over anything that catches the light or catches my eye. Light can make things look a lot worse sometimes. I drag my index fingernal over machined surfaces such as bearings and journals. If a scratch or gouge or burr catches my fingernail, I consider it "too much".

2. Using a small scraper, take down any burrs or raised metal in the bronze bushes which might have caught your fingernail. Scrapers can be made from a piece of broken hacksaw blade (radius the corners so it does not dig or gouge the bronze), or a small three corner scraper or bearing scraper.

Using something like a small three-corner scraper (make from a piece of old triangualr saw file), put a very small chamfer on the corners of the bushing bore mouths. This "breaks the corners" and may clean off any burrs that developed during previous owner's adjustment or reassembly efforts. The three corner scraper will put a nice chamfer on if you use a drawing motion, kind of "slicing" or "shearing". When you use a three corner scraper correctly, it will not dig in, nor will it chatter. You want to make a tiny chamfer, not more than about 1/32" x 45 degrees. This breaks the corners and makes it less likely you will ding or push up the bronze during reassembly.

Get some "Scotchbrite" abrasive pads of the finest grit. Using something like penetrating oil or kerosene (I believe you might call it "parafin") amd the Scotchbrite pad, lightly polish the inside of the bronze bushings. Wash the bushings well using solvent (I use automotive brake parts cleaner) and paper shop wipers. Make sure the bearings are thoroughly cleaned inside and out.

3. Give the inside of the bushings the next test: lightly drag your fingertip (assuming is not heavily callused) over the bronze inside of the bushing. It should be smooth, nothing "catching" your fingertip.

4. Using a fine hard pocket oil stone (I use either an "India Medium Hard" or an "Arkansas Hard" depending on the condition of the parts), tone off the journals. All you are looking to do is break the surface glazing and take off any miniscule burrs or sharp edges to any ridging or scoring (result of wear). Use the oil stones in a criss-cross pattern and use something like kerosene or penetrating oil with the oil stones. Again, use the fingernail test on the journals to be sure there are no ridges or sharp-vee scoring. You are not looking to remove metal, just "kiss off" the surfaces of the journals.

5. Try assembling the spindle and rear journal. It should fit very snugly, but not need to be driven on with any real force. Make sure the shaft key for the rear journal is free from burrs as well. Do a trial assembly of the spindle and rear journal to be sure it goes together without having to beat on it.
The rear journal has to move on the spindle to set the sprindle bearing clearance and end play.

6. When you have everything cleaned up, reassemble the lathe headstock. My way of approaching this is to do the following:
1. check the pitch of the threads on the adjusting nuts. This is going to become your built in micrometer.
Measure the length and big and small end diameters of the journals. Do some trig and you will have the angle of the taper on the journals.
If you play with the tangent of the half-angle of the taper, you will get the relationship of axial move (adjuster nuts do this) to side wards move
(bearing side clearance).

2. Reassemble the headstock with just some penetrating oil or thin lubricant on the journals and bushings.

3. Run the adjuster nuts in until you cannot turn the spindle by hand. This is necessary to seat the bushings and to get yourself a starting point.
Do not hammer or put any real torque on the adjuster nuts. Just snug them until you can't turn the spindle. This takes out all the lash or
play.

4. Now we get to the "built in micrometer". If you have measured the pitch of the adjuster nut threads, you will know how far one full turn of the
adjuster nut advances or closes in. If you have done your trig, you also know how much an axial move of the adjuster nuts is going to change
the side clearance of the bearings. Use any available means to divide the circumference of the aduster nut (I'd use the spanner slots as
divisions and take portions of a "slot" as basis for figuring my moves).

5. Back off the adjuster nuts the amount you calculated and gently lock them snug.

6. Tap the ends of the spindle with a piece of hardwood and hammer. This will open up the clearance since the cone journals may well be seated
hard in the bushings.

7. Try turning the spindle. If it turns free, check side clearance using a dial indicator. To do this:
Mount a dial indicator so it is at 12:00 on the "register" or collar of the spindle. Zero the indicator.
Put a piece of hardwood such as a hammer handle in the bore of the spindle. Push down as hard as you can, estimating 50-75 lbs of force.
See how the indicator moves and re-zero it while pushing down on the hardwood handle.
Pull UP on the hardwood handle, again estimated 50-75 lbs of force. Note the indicator reading. This is your radial or side clearance in the
bearing. 9100 has a good value for typical side clearances. If you do not read at least 0.001" on the dial indicator, back off on the adjuster
nuts a very small amount. Again, your "built in micrometer" based on the thread pitch and angle of the journal cones is your guide. A nudge
of the adjuster nuts is usually sufficient.

8. Once you have the adjustment, you will need to lock it in. This means using two spanners. As crazy as this sounds, if you tighten the locking nut against the adjusting nut, you may actually change the amount of clearance in the bearing. Pulling the lash or any slight slop out of the threads is the reason. After you lock the adjuster nut, recheck the clearance and feel of the bearing to be sure.

9. Once you have the bearing clearances set, put some light oil (ISO 46 or perhaps a touch lighter) into the spindle bearings and roll the spindle by hand. Feel how it stops. It should glide to a stop. If it stops abruptly or with a noticeable "jerkiness" when you stop turning the headstock pulley, it is too tight.

10. If the spindle glides to a stop, you are ready for a heat run. Belt up the lathe and run at its lowest speed. Keep feeling the bearings for warmth. If the spindle seems to be getting hot in a hurry, stop the lathe immediately and flood the bearings with more oil. When the bearings cool, readjust and open the clearances slightly. You are going for a balance between enough clearance so the lathe spindle can run without overheating/seizing, vs tight enough clearance so the lathe can turn stock without the stock "climbing the toolbit".

11. My own judge of spindle bearing heat is crude. I use the back of my hand, like I'd feel another person's forehead for fever. If the spindle
bearing housings on the headstock are so hot you cannot keep a hand on them, they are too hot. 140 degrees F, if you have means to measure the temperature is the upper limit. A "nice warmth" is what you need to feel when the spindle has been turning for 5 minutes or more.

12. The heat run is done for 5-10 minutes at lowest speed (not in back gears, but "direct" belted). Once the spindle reaches temperature and seems to have stabilized, stop the lathe and move the belt to the next step of the cone pulleys to speed it up. Repeat the procedure for feeling and checking temperatures for each step of the cone pulleys until you have the lathe running at maximum spindle speed.

13. Once you have made your heat run, you can go to the next step. That is to chuck a piece of round stock, say 1" diameter, and take a cut on it. By not having the stock supported on the tailstock center, you get to check how rigidly the headstock bearings are supporting the spindle.

Points to remember:
-Bronze has a greater coefficient of thermal expansion than steel. Spindle clearances that seem loose when cold will "tighten up" or "close up" as the lathe is run. As the spindle and bearings warm, the clearances will get tighter. This is why a heat run is made very gradually when you have had a plain bearing headstock apart and made adjustments to the bearings.

-Plain bearings rely on "hydrodynamic lubrication", or the famous "wedge shaped film" of oil. When running, there ideally is no metal-to-metal contact between the journals and the bearing bushings. Too tight or too loose a clearance and the oil can;t establish and maintain this wedge.

-Oil for plain bearing spindles is a whole 'nother subject for splitting hairs, theorizing, debate and dischord. Old lathes and oldtime machinists did not have a whole plethora of lubricants available nor did ISO designations exist. The majot mistake a lot of people used to make was to run something like 30 weight auto engine oil in their lathe's spindle bearings. This is a bit too heavy. Things got worse once multi-viscosity and detergent automotive engine oils arrived. Avoid using them. I personally use nothing more than "Tractor Hydraulic Oil". This is typically a DTE Medium or DTE Heavy Medium oil. It is mineral based, straight weight, and has anti corrosion and anti foaming additives. Tractor hydraulic oil comes typically in ISO 46 & ISO 68 weights. Either will work. I've been running ISO 46 in the headstock bearings of my Southbend Heavy 10" lathe and Southbend Light 10" lathe for many years.

-Use your senses and your head, and go slowly with the work of putting the lathe back in service. A lot of what is needed to put the lathe back in service is simple, no reliance on fancy instruments (other than a dial indicator). No need to overcomplicate things.
 
Thanks for the responses, particularly your very detailed instructions Joe. What confuses me about this process is the outrigger shaft pressing onto the back of the spindle via the steel ball - I think that takes the place of a thrust washer at the chuck end, but also has the effect of pushing the lock nuts and rear journal into the bush and causing over tightening - what would be a sensible procedure to follow for adjusting the backlash by using the locknuts on the spindle AND that preload rod? You can see it in the photos - between the gear on the end the spindle and the cast bracket at the back is a steel ball and the threaded shaft presses onto the spindle and has it's own locknut. I'm sure the original manual had all this information but I don't even know what make this is. Every time I think I have it right, it isn't.:willy_nilly:
 
Costa:

My belief is that you adjust the bronze bearings/cone journals as I described. Some end play is inevitable. Get the side play so you have 0.001"-0.0015" max. Because of the tapered journals, you will also have some end play. Now, this is where that outrigger/ball bearing come into its own. The end thrust (as when you might be turning work, feeding towards the headstock) will want to jam the spindle axially towards end of the spindle where the outrigger/ball thrust bearing is located.If this were allowed to happen, it could take the clearance out of the front cone journal and open the clearance on the other (movable) cone journal (outrigger thrust bearing end of the spindle). Obviously, something has to keep the cone journals centered in the bronze cone bushings to maintain bearing clearances. This is where the outrigger thrust bearing does its work.

Here is what I suggest:

1. Adjust the cone bearings without doing anything to the ball thrust bearing. The spindle and cone journals needs to be able to float in the bronze bearings. This lets you get the side-clearance adjusted. Some end clearance will be inevitable.

2. Using a dial indicator on the end of the spindle (pick either end), push the spindle axially until it stops ( I like to say "hits hard"). Zero your indicator.

3. Push the spindle back in the opposite direction against the dial indicator. When it hits hard with about 75 lbs of force on it, read the indicator. This is the total axial clearance in the spindle.

4. Push the spindle back towards the outrigger ball bearing with about 75 lbs force and re-zero the dial indicator against the nose of the spindle.

5. Set up the ball thrust bearing and start "jacking" against the end of the spindle at the outrigger. Get about half the total axial clearance for movement on the indicator and lock in your adjustment on the ball thrust bearing. This should center the cone journals in their bronze bearings. When you take a turning cut, feeding towards the headstock, the ball thrust bearing will see to it that the front cone journal never does "bottom" in it's bronze cone bearing.
 
Might this lathe have been made by Beyer Peacock, locomotive builders? They also built shop equipment, so as to equip the repair shops of their locomotive clients. This is a looong shot, but maybe.........
 
Thanks Joe, that makes complete sense. I've done it a little like that but without that level of accuracy, though it's not binding or sloppy any more. Your method seems pretty foolproof. There's a lot to do and I'm not very well equipped to do it. The pulleys drive the spindle via a large gear keyed to the spindle but with a what seems to be to me a stupid method. The pulleys lock to the gear via a single worm screw towards the edge of the gear - not threaded into the pulley just sitting in a recess - when you want to use the back gear you undo the worm screw to clear the pulley recess and the pulley then freewheels. Where the worm screw meets the pulley there are two receptacles in the pulley assembly, both chewed up and worn, so welding and re-machining required, not a very good system really.
Also as a consequence the gear is a little sloppy on the spindle, the channel in the gear has been bashed around and isn't a great fit with the key any more. And there's about 1.4mm end float in the gear/pulley assembly between the spindle bearing so I'm guessing I'll throw in a thrust washer just to take up the worst of the slack but leave enough so it doesn't affect the spindle bearings.. Easiest fix would be to attach the gear to the pulley semi permanently and lose the back gear functionality, or at least drill and tap the pulley so it's locked to the gear properly and can be removed reasonably quickly for back gear operation. All part of the learning curve.
I wish I had a lathe so I could fix my lathe :scratchchin: LOL
Loco that IS a bit of a longshot, I'm thinking, as I'm in Australia.
 
New clearer photos

I've taken photos with a better camera.

https://www.dropbox.com/sh/eitfbug3qjuckh5/LfTUT0CIzr

By the way, has anyone ever seen this method of tailstock alignment - there HAS to be something missing, because for this method innacurate is an understatement - screw heads pushing on opposing sides then clamping the tailstock so it doesn't move... Any suggestions for how to fix this little problem?
 
The only picture of the tailstock I see is looking from the handwheel end, not showing much of anything. Some lathes use two screws pressing against the front and back, some use two threaded into the tailstock body and in tension to do the same thing, but one or the other is typical. One thing I have always hated about them is that they will give you something like 1/2-13 slotted screws, not even hex heads, and expect you to adjust them to a thousandth or less, 1/77 of a turn, with a screwdriver.

Bill
 
The only picture of the tailstock I see is looking from the handwheel end, not showing much of anything. Some lathes use two screws pressing against the front and back, some use two threaded into the tailstock body and in tension to do the same thing, but one or the other is typical. One thing I have always hated about them is that they will give you something like 1/2-13 slotted screws, not even hex heads, and expect you to adjust them to a thousandth or less, 1/77 of a turn, with a screwdriver.

Bill
That one picture pretty much shows the situation, one screw front and back threaded through a boss in the center of the tail stock at each end. The screw heads are diagonal to each other if that makes sense? The screws are about 2 millimeters narrower than the ways at each end, so you can stuff around for ages centering it, but there's always the chance it will twist when you tighten the big lock nut, because of that 2 mill clearance at the thread end. Is this normal or should the screws be a good close fit between the ways and they've worn away over the years or been replaced with incorrect items? Sorry if my questions are simplistic, I have no experience with such things.
 
Costa,

That is an unusual arrangement. It looks to me as though the tailstock is from another, bigger lathe, and is missing its base. The adjusting screws as shown in your photo would quickly wear grooves in the inner sides of the ways, and, as you said, would tend to skew the tailstock rather than shift the whole tailstock sideways.

A more usual arrangement is as described by 9100 above , and looks like the photo below. One screw either side of the tailstock base pulls (or sometimes pushes) on a central projection under the top half of the tailstock casting to move the whole top half of the tailstock across the base casting to provide the adjustment.

I can't think offhand of an easy fix, but someone with more relevant experience will probably come up with an idea.

Regards,

Frank.
 

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Yes it seems very strange, though the tail stock looks like it belongs to the lathe - the height is correct, it just, as you say, skews whenever you try and move it. The only thing I can think to do is have a plate machined to fit between the ways and use countersunk screws in the same arrangement to take care of alignment, though that neams I'd have to pull it out to adjust it, put it back in, check, pull it out etc. The perils of old machines...
 
Now I see what you are talking about, the little boss that sticks down between the ways. I suspect that there were gibs in there originally. I can't imagine a manufacturer that could otherwise produce what seems like a pretty good machine making something that poor. Does the rib, or whatever you want to call it, extend the length of the tailstock?

Bill
 
Now I see what you are talking about, the little boss that sticks down between the ways. I suspect that there were gibs in there originally. I can't imagine a manufacturer that could otherwise produce what seems like a pretty good machine making something that poor. Does the rib, or whatever you want to call it, extend the length of the tailstock?

Bill
LOL it gets worse, the spindle is mounted the same way, though the bolts in the bosses look original and are a better fit between the ways, but even then there is still clearance. The bosses do not extend the whole way. I guess it's not so much of a drama with the spindle - I'm assuming I align it carefully using a straight rod in the chuck and tighten it down, it doesn't need to move. The tailstock, now that's another thing altogether. A flat plate that fits snuggly between the ways and around the bosses is what I'm thinking, though some way of making it easily adjustable and reliable hasn't popped into my little brain yet.
Beginning to understand some advice regarding lathe ownership from some wise soul who recommended not buying a lathe to work on but a lathe to work with if you're a beginner!
 
Tractor Hydraulic oil should never be used for plain bearings.

It contains additives to increase friction to allow it to be compatible with modern tractors that have wet brakes and clutches.

Iso aw series (aw46 etc) however contains additives that reduce friction to enable them to be used in swashplated hydraulic pumps.
 
Flip the other screw under the tailstock around so they both point the same way. Then put a spring with brass shoe just inboard of each screw, on the head side. The screws will press one way, the springs will press the other. Probably have to put a pin down the center of each spring to keep them from popping off. Its not as good as a 'real' gib, but it will work.

allan
 
By the way, has anyone ever seen this method of tailstock alignment - there HAS to be something missing, because for this method innacurate is an understatement - screw heads pushing on opposing sides then clamping the tailstock so it doesn't move... Any suggestions for how to fix this little problem?

Not uncommon on this type of lathe and a lot of other pommie machines with flat square beds. Usually it is set up so that the screw heads provide location against the inside of the ways and for this purpose the end of the stock can have 2 separate screws in a single threaded hole, 2 threaded holes with 2 opposing screws or a single screw with a pair of nuts.
 








 
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