Run out on lathe chuck

[graduate_owner]

I acquired a chuck which has the wrong thread for my lathe, and a friend has made me an adaptor. Unfortunately there is about 1/2mm run out and I am not sure if that is significant for a wood lathe. Does anyone know what typical run out is, or what the maximum acceptable run out should be?

K

 

[CHJ]

My chucks run within 1-2 thou. you are talking in the order of 20 thou.

Would not be happy getting that run-out on a re-mounted wood piece, and definitely not on a chuck.

Suspect you are getting quite a bit of vibration if it's a heavy chuck.

 

[graduate_owner]

Yes, there is certainly vibration. It looks like we will have to do some more machining on the adapter. Or start again.

K

 

[dickm]

Grandmothers, eggs and all that, but is your mate remembering it's the plain regaster and the shoulder of the spindle that dictates alignment/runout, not the thread?
From repeated experience making adaptors, unless the nose of the metalworking lathe replicates that of the Grad (unlikely) you really need to have a true running mandrel with appropriate thread and register to do a precision job.

 

[Random Orbital Bob]

Also, if it's a common/popular chuck, you can buy adaptors suitable to convert most chucks to most spindle thread sizes which should work off the shelf with the sort of run out tolerances Chas documented.

 

[CHJ]

....
From repeated experience making adaptors, unless the nose of the metalworking lathe replicates that of the Grad (unlikely) you really need to have a true running mandrel with appropriate thread and register to do a precision job.

Yes can be a good few hours work to sort out a one off on a standard workshop lathe.

For those that have never contemplated doing such something along the lines of this process is required at least it would be for me with the limited tooling I have.

1. Need the recipient wood lathe spindle in hand or job one:- Turn a replica of the spindle nose with register to fit an existing fitment such as a faceplate or chuck.
2. Bore & thread insert inner and register socket in suitable metal blank using spindle nose to test fit.
3. Either refit replica nose spindle in lathe ensuring no run-out or turn another one. *
4. Mount threaded blank onto this undisturbed spindle nose, (ensures blank is running true on register). and cut outer thread and any chuck register using new chuck for correct fit test.

* Somewhat depends on size and accuracy of the working lathe and chucks/collets. which may be able to use the Wood lathe spindle or replica nose easily for stage 3.

 

[graduate_owner]

Thanks guys,
The wood lathe is a viceroy with 1 1/2" x 8 tpi thread which is the same as Boxford, but we are using a Colchester to do the adapter. The chuck fitting is just a parallel hole with grubscrew so just a spigot is needed on the adapter. I am thinking now to turn a suitable viceroy thread + register mandrel, reduce the spigot, turn a sleeve to fit over the reduced spigot, then turn sleeve to final diameter and secure both chuck and sleeve to spigot with a grubscrew. If I turn the sleeve up first then I can complete the job without removing the adaptor from the colchester. Should have turned up the mandrel in the first place. As someone once said to me - if you don't do the job right in the first place it will turn around and bite you in the @rse sooner or later. Dead right.

K

 

[Retire2004]

Hi Guys,
Keith, on reading this thread I began to get excited thinking that this chuck was intended for your Graduate (as I think did Dick M). The reason for my excitement was that my metal lathe is also a Harrison (L 5) with, yes, a 1 1/2 x 6 TPI spindle, but slightly longer register. This has great advantages as chucks and faceplates are interchangeable between the L5 and my Graduate and also provides a virtual replica spindle as discussed above for making special adapters etc.
However, I may still be able to help as I have, surplus to requirements, an ISO chuck flange adaptor which is 1 1/2" x 8 TPI (bought in error thinking it was 6TPI). From memory, I think the flange is 4" dia. with a 70mm spigot and 3 bolt holes. Could the back of your chuck be machined by your friend to accept this adaptor. As you may remember we are not a million miles apart (SA18) PM me if interested.
Kind regards, Tudor

 

[graduate_owner]

Hi Tudor,
I have sent you a pm.

K