As Gray stated: the thread does nothing other than pull the chuck onto the register, however, if the thread feels tight it is likely you have got swarf into the threads, and under these conditions the thread certainly can throw the chuck(s) out of alignement. It is not always easy to see the swarf – if it was a broad ribbon that got trapped it is almost like electro-plating in there! If all your chucks now seem tight then it's likely the swarf has attached itself to the spindle thread rather than inside the chuck.

I would be very wary of using a die on the spindle (and a tap in the chuck for that matter, but I don't think the problem lies there) unless as a last resort. Try using a pointed tool – scriber or something – and work all around from start to end.

In future, if there is any hint of the chuck feeling tight as it's screwed on then stop and remove it. A short session with an old toothbrush will work wonders. Once you have forced the chuck on it becomes much more difficult to get off (yes, I learned the hard way on this one).

Hello Alex,

Another possibility might be a shallow bruise on the chamfered mouth ot the chuck register if this trouble was confined to only one item. But as it appears to be across the board then I go with the others on the thinking of fine embedded swarf now incorporated with the spindle thread.

A suede brush with brass wires might shift it, a little kinder to use than a standard wire brush. I would use taps on chucks only with reservation, a threading nut on the spindle would be best avoided I think.

As Chris says, don't force it on, big mistake. A little moly grease on the spindle thread might help ease things a trifle but look out for it breaking down and allowing 'pick up' in metal to metal contact, leading to a seize.. It it feels tight with moly grease, undo it pronto. The grip on the thread should NOT be that tight, the register does the alignment.

I hope you get it sorted out satifactorily

Brian.

Alex, just for peace of mind you cold try running an indicator one the register faces. A 'blip' on the indicator might detect a bruise you can't see.

Neil

Hello Alex,

Thank you for the update, it is always heartening to have an explanation for puzzle like that.

I can see no reason now why negligible run out should not be possible. Stub Mandrel's advice above should show the way. If the register and shoulder are all as they should be, then the final move is to look again at the chuck and faceplate registers which might also be revealing after your 'rethreading', I would try marking surfaces with felt tip markers and run them together to see where any high spots exist..

Remember it is the register and shoulder together that does the location, the thread merely holds things together.

Regards

Brian