Centering Mini Lathe tailstock – advice required

[Chris VeitchParticipant @chrisveitch14689]

[Chris VeitchParticipant @chrisveitch14689]

I have a fairly newly-acquired Warco Mini Lathe and the tailstock appears to be slightly off centre as delivered. I've seen descriptions of balancing a piece of thin sheet between centres to determine alignment, bit other than this there doesn't seem to be much in the way of advice on how to achieve correct lateral alignment.

Coming from a Unimat with a fixed tailstock I'm a bit green to this so would appreciate any tips or advice.

Regards,

Chris Veitch

[Neil WyattModerator @neilwyatt]

There are two screws, one at the back of the headstock and one underneath. The tailstock clamp screw also locks the arrangement, so it is a bit of a fiddle. I made a brass gib for mine to make it easier to get free adjustment, but for now I suggest you go with loosening both screws then retightening to get as near to smooth but shake-free movement as you can get. Make sure no paint has wicked onto the sliding surfaces. Lock the tailstock barrel in place using normal force.

A basic alignment is just to have a centre in head and tailtock and align them using short sight or a loupe magnifier. If both centres are sharp and accurate this gets you surprisingly close.

Interposing a steel rule will highlight any misalignment very well.

A practical test is simply if turning between centres gives you a bar of constant diameter – you can turn away a lot of bar chasing (and overshooting) the last fraction of a thou this way.

Best practice is a dial test indicator held in a chuck and used on the tailstock outside surface to check it reads the same at both sides (and hopefully up and down).

The 'practical' route, as used by LBSC and others is a long 'test bar' between centres with the centre turned down by 50 thou or so to give you a long 'cotton reel' with flanges at the ends. Turn the 'cotton reel', and then skim the tailstock flange lightly, reverse the bar and skim the other end at exactly at the same setting. Use an indicator held in the toolpost to take readings from the flanges and when they both indicate the same the bar is parallel.

Keep the bar safe or future use.

I don't do this as I'm the sort of person who ends up using the bar to make something…

Neil

[Neil WyattModerator @neilwyatt]

Hi John,

I hesitate to disagree with someone of your experience!

Yes you can do it that way, but three issues: (1) it's hard to skim the flange at the headstock end if the driving dog is in the way (you need another inch or so at the end for the dog), (2) it relies on you being accurate with your micrometer, which takes more skill than reading a DTI and (3) if you're not very good at this, it can take many cuts to get it right and your flanges might disappear altogether!

Assuming the tailstock is reasonably aligned, (within a mm) and reasonably long my way works, and I think it's easier for a beginner.

Whichever way you make it, once you have a centred bar turned the same diameter at each end, you can re-use it using a DTI or plunger gauge without having to do more cutting.

Neil

[Chris VeitchParticipant @chrisveitch14689]

Thanks for the tips, gents – I've now managed to get it reasonably correct. I initially tried the DTI in the chuck method and then reckoned that I must have set up it up incorrectly because it couldn't be THAT far out.

I then tried it with centres – only one is supplied with the machine (thanks, Warco) and I had to just taper turn a bit of scrap for a second one and leave it in the 3-jaw (and don't get me on about the quality of the taper slide…). Anyway this revealed that it really WAS that far out and a bit of gentle adjustment with the steel rule method seems to have sorted things out.

Now all I need to do is find some Warco-coloured paint to match the bits which came off the poorly-finished tailstock when tapping it over, and yes, I did use a block of wood!

Chris

Edited By Chris Veitch on 09/08/2014 08:36:15

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