Sieg C0 tailstock alignment

[Sonic EscapeParticipant @sonicescape38234]

My C0 lathe has a severe tailstock misalignment. The misalignment is visible without turning a test bar. Even worst, it is in the horizontal plane.

The tailstock is not adjustable. I discovered that a 0.25mm shim mounted here improves the alignment.

I’m thinking to glue somehow a shim there. Or is it better to try to grind one side of the tailstock V groove? I could add sandpaper one side of the bed inverted V and slide the tailstock on it. But is it possible to grind in this way ~0.25mm of cast iron?

[BazyleParticipant @bazyle]

First check that the tailstock base on the ways is clean and has no embedded grit/swarf. Does the offset change with tailstock extension? Then check your centre is true, then that the MT socket in the tailstock barrel is true, then that the hole in the tailstock body is true.

[Dave SParticipant @daves59043]

Is the center low? (Horizontal plane)

Does it shift when the clamp is tightened?

Dave

[Bazyle]

On Bazyle Said:

First check that the tailstock base on the ways is clean and has no embedded grit/swarf. Does the offset change with tailstock extension? Then check your centre is true, then that the MT socket in the tailstock barrel is true, then that the hole in the tailstock body is true.

Everything is clean. The offset doesn’t change with extension level (good sign). The center is true because the offset is the same if I rotate it. So the hole in the tailstock must be true. The problem is in the V grove at the base.

By the way, MT was not invented yet when C0 was made. The center has no taper. It relies entirely on the pressure on the quill shoulder! As a result here is how much play it has if it is not seriously pressed against the tailstock quill. But this is a design limitation, nothing to do about it.

And this is with the quill and tailstock locked!

[Dave S]

On Dave S Said:

Is the center low? (Horizontal plane)

Does it shift when the clamp is tightened?

Dave

It is not low. The offset is visible when I watch from above. Clamp has no effect. Neither locking the quill.

[BazyleParticipant @bazyle]

Because one of the lathe bed slideways is flat another possibility is that if that face is reduced it will tilt over. This would be easier to do. Try a 1 thou feeler under there and see how much it affects the alignment which I expect is magnified several fold.

[DiogenesParticipant @diogenes]

Yes, it will be okay to glue the shim with loctite 608 / 638 or equivalent – I’ve had a strip of shim stuck on my Myford carriage for 5 or 6 years.. ..make sure everything is completely grease-free..

Much better to stick shim on than it is to take metal off the base.

[V8EngParticipant @v8eng]

Some C0 machines (early ones I think) were fitted with an adjustable twin collar device presumably to correct the tailstock issue.
Do you know the history or age of your lathe because the device may have gone missing at some stage, if it ever was there. Photo of mine (behind the chuck) attached.

I know this does not help with your immediate problem unless you can find one or make one up.

[howardbParticipant @howardb]

It appears that a later model of the Seig C0 baby lathe were fitted with a laterally adjustable tailstock.

www dot amazon dot com dot au search for Seig C0 baby lathe

For some reason I can’t post that URL to show the image.

Click on the main picture & go the thumbnail showing the tailstock, click on it to enlarge it and you should be able to see the mortise and tenon type sliding lateral adjustment locked by a capscrew at the right hand side of the tailstock.

Where’s Ketan when you need him? Any possibility of contacting him?

[howardbParticipant @howardb]

[howardbParticipant @howardb]

There you go.

[David George 1Participant @davidgeorge1]

If I was to shim the tailstock I would put the shim between the base which slides along the ways and the top casting which holds the barrel. I would check the centre by rotating a dial indicator held in the chuck and rotating to see the offset and you could adjust the side to side setting as well. When checking this way also remove the centre and set the dial indicator inside the bore of the tailstock and look for any deviation as well.

David

[Dave SParticipant @daves59043]

I made a new center for my Unimat (basically the same lathe), as the original one had poor pointyness and poor fit into the tailstock barrel.
The new one is a tight sliding fit.

 

[Engine BuilderParticipant @enginebuilder]

V8Eng, Please can you explain how that collar arangment works.

David

[old martParticipant @oldmart]

I favour the shim solution, it is reversable if you find another problem. This is where a test bar comes in handy, they are available from about 7 1/2″ long upwards.

[old mart]

Yes, it looks like a shim is the best way to go. I drank a beer can but the aluminium is way too thin. I’ll try tomorrow to eat some tuna.

On old mart Said:

I favour the shim solution, it is reversable if you find another problem. This is where a test bar comes in handy, they are available from about 7 1/2″ long upwards.

How can a test bar help here?

On Engine Builder Said:

V8Eng, Please can you explain how that collar arangment works.

David

Yes, I’m also curious.

On Bazyle Said:

Because one of the lathe bed slideways is flat another possibility is that if that face is reduced it will tilt over. This would be easier to do. Try a 1 thou feeler under there and see how much it affects the alignment which I expect is magnified several fold.

Yes you are right, that is better than grinding the V groove. I’ll try it if for some reason the shim doesn’t work.

[V8EngParticipant @v8eng]

Have to admit that I’ve had the C0 for so many years now it’s difficult to remember (age related) and it was a just do once type of thing.

I kind of think the two sections could be loosened from each other using the hex head screws and one section set over relative to the other.

i will see if there is still any paperwork tucked away (may take many days).

 

[Engine BuilderParticipant @enginebuilder]

V8Eng, I see the screw now so looks like one part srews to the tailstock and the other to chuck. parts held together with cap screws with oversize holes in the tailstock part.

Same as you would use to mount a chuck to a backplate but without the register.

I have been considering making a similar set up on my C0 lathe.

[Martin of WickParticipant @martinofwick]

<p style=”text-align: left;”>Perhaps check the headstock end for burrs swarf and correct seating and alignment etc.  if the spindle had an internal MT you would use a test bar to confirm headstock alignment.</p>
If you want a source of shims, just get some cheap feeler gauges and use those. You may have to shim both head and tailstock.

These lathes are not designed or sold as precision tools so you may have to accept some level of compromise.

In the worst case, you could make a ‘set over’’ centre arrangement if it proves difficult to shim to alignment.

 

[Howard LewisParticipant @howardlewis46836]

Howardb’s picture shows that the tailstock is in two parts and can be set over relative to the base, but there are no adjusting screws.

We had the same problem with a C1, but used a G cramp as a means of delicate(?) adjustment between upper and lower parts, before fully tightening an Allen screw under the base.

Remove the tailstock and investigate before doing anything that cannot be easily reversed.

You will need an Alignment bar (Bought or shop made with the 4 jaw chuck and probably a steady; or another lathe with a 4 jaw, mag base and DTI)

Howard.

[BazyleParticipant @bazyle]

Another point. Put blue on part of the main bed and gently set the tailstock down on it. Then examine the imprint on the underside of the tailstock to see if there are any areas not in contact. This might indicate a bend or twist or a high spot you can scrape.

[MacolmParticipant @macolm]

One way to provide an offset is indeed using two nested eccentric sleeves. If the housing can clamp the outside diameter of the outer eccentric, then by slotting it lengthwise both sleeves can be simultaneously clamped. Adjustment is hard going unless additional helping features are added!

[Martin of WickParticipant @martinofwick]

<p style=”text-align: left;”>If you need an extempore test bar, you could use some 10mm silver steel (larger diameter if will fit through the spindle). Let 4 to 6in project in front of chuck and run a DTI mounted on x slide along the side length of the bar using the carriage feed.</p>
This will at least help confirm if the headstock/spindle/chuck assembly is aligned with the bed ways.

The other way is to take some light cuts on a 4 in piece of bar so it is all bright metal then measure each end with a micrometer. Zero difference indicates all is good at the headstock end.

[Engine BuilderParticipant @enginebuilder]

I have been in the workshop and made up this adustable chuck fitting. It works well. Previously when centre drilling the drill tip did not seem to be on centre.

[Engine Builder]

On Engine Builder Said:

I have been in the workshop and made up this adustable chuck fitting. It works well. Previously when centre drilling the drill tip did not seem to be on centre.

That looks good & be interesting to hear how you get on with using it.

[Author]

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