Tail stock spindle out of line .

Been machining a long shaft between centres and did get the size required at both ends after a bit of tweaking.

Had machined a centre in the headstock so was true running when sliding tailstock centre to it both were at the same height.

When I locked the tailstock spindle its centre lifted.

It's an early Warco 600 lathe and the way the spindle is locked it is pushed up by the keyway pin.

Seems the spindle has too much clearance at top of tailstock casting.

Apart from maybe making a new spindle and rebore the tailstock wondered if there is another way to clamp the spindle instead of pushing it up to lock it.

My Chester Craftsman lathe has a similar problem, seems to be too much clearance between the parts.

I drilled and tapped to fit three screws, one on top and one each side to take up the play. Not ideal, but it helped.

I think the real answer is to rebore the the tailstock and make a new spindle. It,s not a very good design, perhaps if the tailstock was split and clamped it might work better.

Is the height error the same at all extensions of the tailstock barrel?

I suppose you could measure the excess height when clamped and take some metal off the joint between the two parts of the tailstock. Another option is to glue a bit of brass shim in the bore of the tailstock (top quarter only) if the barrel is a rattling fit in the tailstock.

Martin C

A pet hate of Tony at lathes.co.uk but I see what you mean!

I have Antony Mounts modification articles to his Warco 600 GB he made a better clamping arrangement but would possibly still lift the spindle.

As a temporary test this morning coated the spindle in Rocal dry moly paste.

The dial gauge showed no movement when I was clamping it how long it lasts is anybodies guess.

The dry moly paste is from my flash steam hydro days the highly stressed cam and follower was coated in it and saved them from damage, oil was a waste of time.

A bit of my history a past top BDA rally engine builder his were better than some of the works engines.

Talking to him at his used machine tools saleroom about the cam problems he reccommended trying the dry moly paste.

He used to coat and press fit the BDA liners with it he never had any scuffing issues

Windy:

Does the moly combine in some way with the treated metal?

Myfords changed the design of the Super Seven tailstock to avoid this lift problem.

You will get the minimum deflection if you have the absolutely minimum ammount of tailstock barrel projecting. That will be impossible all the time. Getting a test bar with the same size Morse taper as the tailstock will allow full checking of the alignment and the ammount of lift. The bad fit is caused by wear or a poor fit when new, or a combination of both.

It's many years ago now, but I remember Anthony Mount bought a new Warco BH600 lathe which he was pleased with, but just did a few tweaks to it, or fine tuning as I vaguely remember he called it.

I seem to remember he commented that the tailstock quill was a good fit in the casting, and I think he made a collar to fit over the quill and screw to the face of the casting but this was just to house a seal.

So if your quill is a sloppy fit in the tailstock bore, and it is the bore that is worn or it's all just a slightly sloppy fit from new, you could machine a thick collar that is a close sliding fit over the quill and secure it with screws and maybe dowels to the end face of the casting, assuming the end face is machined flat and square to the bore. The clamping method that your tailstock has wouldn't then matter or cause a problem if there is no clearance around the quill.

I have a 16 year old large Warco 1330 lathe with a tailstock quill that is a firm push fit in the honed bore of the casting, just like my old Boxfored lathe, with no play at all. The quill on my Warco lathe is clamped by a Bronze bush either side of the bottom of the quill that are pulled together by a lever, the radiused ends of the bushes then clamp the quill firmly. This is a common method used on lathes but even this would still deflect the quill if it were a sloppy fit in the casting.

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I can only go on my use of it am reasonably sure in my applications it forms a thin coat.

Once I coated the flash steam poppet valve with the red heat involved when on peak form it seemed to alter to another form and became abrasive.

After that when high temperatures are involved I used Grathos.

Was given an aerosol of some moly think it was used on a type of extrusions die it really stuck to the metal.

That form of clamping only causes problems if the two parts don't fit together well.

The Smart & Brown model A uses half of that system which would certainly lift if there was slop. The drill mill and the Tom Senior light vertical use an exact replica on their quills, and I have tested them both. Using an optical sight in the spindle focussed on a target mark, I tightened up the locks and there was no noticeable movement in either mill. The line spacing is 0.025mm, and movement of a tenth of that is visible.

The Smart & Brown model M is the same as the model A. As it pushes the barrel away from the front towards the back when clamped it is easy to adjust the tailstock to account for any wear by moving it side to side to get it correctly positioned when clamped.

Martin C

Wild idea ... maybe not for Windy, but for the back-burner:

Put an ER Collet on the nose of the tailstock body.

MichaelG.

Thanks, Windy.

My only experience of moly is of the liquid variety which was very effective in silencing a noisy Sunbeam Mk III gearbox.