Mellor lathe.

[WorkshopChris]

What caused it to lock? main spindle

No mate. Slow speed. It didn't clonk or anything. Just stopped. There is no visable signs of wear . Will put it back together tomorrow as just try again. I now no it's not a tool problem.

What did it take to free it up?

 

[Ian James]

@spencer 427 is that a square inset you were using ?? Did the bearing feel warm when it locked up and is there a possibility that you over tightened the thrust bearing when refitting because if you did that may of caused the other bearings to run tight as soon as they start to get warm they will tighten up

 

[God mode restorations]

What caused it to lock? main spindle

What did it take to free it up?

After I stopped it. I tried turning the chuck. So I slowly took the caps off. I have spun the spindle by hand and all looks good. The only thing I can think of is I might of put to much preasure on the centre forcing the spindle back a touch

 

[God mode restorations]

@spencer 427 is that a square inset you were using ?? Did the bearing feel warm when it locked up and is there a possibility that you over tightened the thrust bearing when refitting because if you did that may of caused the other bearings to run tight as soon as they start to get warm they will tighten up

yes square insert. Bearings didn't feel warm. I could of put to much on the centre.

 

[Ian James]

After I stopped it. I tried turning the chuck. So I slowly took the caps off. I have spun the spindle by hand and all looks good. The only thing I can think of is I might of put to much preasure on the centre forcing the spindle back a touch

@Spencer427 that is a possibility how badly worn is the rear more taper does your centre for in to it tightly ??

 

[God mode restorations]

You're shimming the top bearing blocks when refitting, to allow some slight expansion clearance?

They never had any shims Matt. And I can't find a good picture to see if they had any

 

[God mode restorations]

@Spencer427 that is a possibility how badly worn is the rear more taper does your centre for in to it tightly ??

The taper looks ok. And nothing slips. But I did get a mt1 reamer to just give it a clean

 

[God mode restorations]

Only thing I can think of that would cause the spindle to lock is to much preasure on the centre .... But can get my head around why it would cut nice then go crud. Everything was ok with no signs of any backlash.

 

[Ian James]

Having to mutch pressure on the centre may of pushed things back a little causing some backlash though !!!

 

[Hood]

Not sure of the head set up but surely the job of the thrust bearing is so that you can not push the spindle back?

 

[Richard.]

nice then go crud.

The Usual reason for a finish to change for the worst mid cut is the tool has suffered on the cutting edge.
Sometimes it’s such a tiny little chip on the end of the insert it’s almost impossible to see. I use a lamp and magnifying glass to check mine sometimes.

 

[God mode restorations]

Evening guys .
Just been down the shed to go through things on the lathe .after a good check I have noticed a fair bit of movement in the rear power feed screw. Back and forth movement is fine. But about 1mm movement up and down. This is where the worm connects to the power feed gear. Could this cause the saddle to kind of float.

 

[God mode restorations]

Not sure of the head set up but surely the job of the thrust bearing is so that you can not push the spindle back?

Yes. But this isn't the original bearing. It was slightly thicker than the original as someone has put three small washers to make up for the extra thickness

 

[Hood]

Ok, as said I don't know the set up without looking back and trying to find a pic of the whole spindle layout but a thrust bearing should be there to take the thrust and the spindle should not really be able to float.

 

[God mode restorations]

The Usual reason for a finish to change for the worst mid cut is the tool has suffered on the cutting edge.
Sometimes it’s such a tiny little chip on the end of the insert it’s almost impossible to see. I use a lamp and magnifying glass to check mine sometimes.

It started of nice on a couple of runs.then mid way would go from a nice finish to really rough and then nice again. Very frustrating to say the least. Especially when it's difficult to pin point why

 

[Ian James]

Ok, as said I don't know the set up without looking back and trying to find a pic of the whole spindle layout but a thrust bearing should be there to take the thrust and the spindle should not really be able to float.

I have just been back and looked at the picture and yes it should in the position it is in

 

[God mode restorations]

O

Ok, as said I don't know the set up without looking back and trying to find a pic of the whole spindle layout but a thrust bearing should be there to take the thrust and the spindle should not really be able to float.

I took a new picture so you can see.

 

[addjunkie]

Cant offer any help but beats watching the dross on tv

 

[God mode restorations]

Cant offer any help but beats watching the dross on tv

Lol. I thank everyone for there help and advice .

 

[Hood]

Ok so if I am seeing that right, the thrust bearing should be adjusted so that the spindle can not be pushed back. It could theoretically come forward and the gears bear on the plain bearings but really most cutting forces, certainly when turning would be pushing.