mini lathe head spindle runout problems

[Aquarius21]

Hi, while chucking in a collet and drill in my mini mini metal lathe
which is no longer produced and parts are not available, I noticed
that there appears to be a wobble of the drill. The guage said
about 5/10,000 at the headstock. While no lathe is perfect
how much can one get away with without ruining jobs?

Any adjustments, etc. I can make or must I assume the
spindle is defective and the whole restoration of the Sartglen
has come to an end?

My thanks, Quincy

 

[Lakc]

Is this the kind of lathe your talking about?
http://www.lathes.co.uk/jason/

 

[Aquarius21]

Hi, yes the lathe was badged as a Jason, New Randa, Perris Pixi and Sartglen Pixi
as detailed at UK Lathes by Tony. All advice welcome! Quincy

 

[Florian]

Hey Quincy

Remove the collet and the drill and measure on the inside of the spindle! (on the collet cone)

If thats ok, then it must be either the drill or the collet. If its not ok, then the runout is in the spindle itself and there is not much you can do...

But just to be shure, if you write 5/10,000 then you are talking about 0.0005" runout..? (Im a Swiss, so not used to this way of expressing small values)

If it is 0.0005" on the collet cone, this would mean 0.01 mm runout, then its not so bad, you just have to remember it when you want to work really precise... (especially if you remove the part during the machinig process to put it into the collet again!)

Runout could also be caused by an inapropriate collet diameter or by a stamping on the shaft of the drill!

The Collet may have a runout of 0.01 mm because of the manufacturing tolerance. I don't know what the max. runout is for your collets but there are standards where the max. runout is declared. (If those collets are included in any standard)

I propose you measure at the cone for the collet first and then we can look for solutions of your problem.. (because it limits the possible errors)

Oh and pay attention if the runout is repeatable!

Florian

 

[Lakc]

Make sure everything is clean and no chips are keeping something from seating. When I do these types of measurement I try to use drill blanks as they are cheap and rather accurately ground, as well as being much stiffer. Unless you need some unobtainium custom bearing, there is not a lot on that lathe that you cant rebuild from scratch.

 

[Aquarius21]

My thanks! I just went down, checked the aluminum faceplate on the lathe for runout
and it was .00017 out. ( if I am reading the guage correctly.) So, this indicates
that it is the collet or bore of the spindle as suggested. I will now have to check
both of those. Question. I read repeatedly that collets are the most accurate.
Is this true? My thanks, and hopefully I can can get this resolved. Quincy

 

[Blogwitch]

Quincy,

If you are getting 0.00017" runout, then a fly farting as it was going past could have caused that.

For a mass produced mini lathe, that is well within tolerances to be expected. But if it is actually 0.0017", then you should really give the backplate a true up.

If you have a well set and trued up collet chuck, then yes they can be classed as being about the best you can use. For larger work, soft jaws fitted to your normal three jaw is the way to go. They are bored on the machine to give true concentricity.


Bogs

 

[Aquarius21]

Time for new glasses- the spindle runout is .005" not .0005. thanks, Quincy

 

[Blogwitch]

That is way too much runout Quincy.

All I could suggest is either get someone to regrind the internal taper to true it up (anything externally you can do yourself), or get a new spindle an hope it is better than the one you have.

Bogs