Dumb question on R8 (i think) spindle

[r-mm]

Yes the shoulder at the bottom of the splines is 30 mm and is a light interference fit to the ID of the bearing at the top of the quill. I cannot see a nut in the grizzly diagram nor my mill that would provide pre-load.

 

[DavidR8]

Isn't part #126 the preload nut in the diagram?

 

[rwm]

If you choose to replace the spindle, it is imperative that you send the original to an experienced member for forensic analysis.
Robert

 

[r-mm]

126 is the 35mm nut that loads the bottom two angular contact bearings. Both spindles appear to have the same nut.

 

[r-mm]

Here is the Prussian blue test with a tool installed in the Collett and the drawbar used

Because it is making reasonably good contact where it has been drawn into the spindle I am now wondering if the taper is correct but the remains of the setscrew significantly damaged the rear of the bore which is preventing the Collett from going further in. The quick and dumb way to test this would be for me to cut the back off a collet to see if I can push it in by hand

 

[rwm]

I think you are probably correct. Now that the spindle is out, can you better see the deep part of the taper? You could make a plug that matches the dimension of the collet and see if it fits. Kind of like a Go gauge.
Robert

 

[r-mm]

I cleaned up the inside of the bore using small flap discs. This definitely helps all of the collets but still I find that and on modified Collett will only draw in maybe a half turn of the nut before it feels like it is bottoming out. I tried removing the small shoulder on the rear - that is the photo in the middle. I get the same result. It is only when I remove some of the length of the collet - on the left - that I can get the drawbar nut to make a few rotations feel it moving in and see the Collett closing down.

I think I may get some more flap discs and continue this effort.

 

[r-mm]

I think you are probably correct. Now that the spindle is out, can you better see the deep part of the taper? You could make a plug that matches the dimension of the collet and see if it fits. Kind of like a Go gauge.
Robert

I made that plug gauge and it tells me the last 5-6mm do not want to seat

 

[DavidR8]

So that would seem to indicate that the bore is not deep enough to take the full length of an R8 collet.
Or is boring the spindle an option?
Is cutting your collet to length an option?
(Totally spitballing ideas here...)

 

[r-mm]

All options. I'm going to have a look with my dial bore gauge to see if I can understand whats doing on better.

Does the rear of the collet contribute to concentricity or can I hog out the spindle bore with the flap discs?

I don't have a boring bar long enough to clean the bore on the lathe but suppose I could change that...