Taper bearing query!!

[lather]

close to finishing the assembly of the headstock.
getting the same problem of the rollers not turning at the top and bottom of the bearing,thought it was the crap in the original bearings causing the problem.
should all the rollers turn, or could this be due to an egged bearing bore ?

[Stustoys]

Hi lather,
Is this with preload on the bearings?

Stuart

[Michael G]

Could be an egged bore - I went to an SKF 'seminar' once and was amazed at the out of round figures they put up for some bearing housings. If you have an internal micrometer you might be able to take some measurements across the bore in various places and see. How you fix it though...

Michael

[lather]

needed to over tighten the original tapers before all the rollers turned, too tight for normal running.
the new bearings seem to be the same, feels tight when turning the spindle, doubt the chuck would free spin 1/2 a rev when giving it a spin by hand.

still getting unusual reading on the run-out, thought i got lucky as the run-out was 0.003mm, it then jumped 0.01mm after 2 turns.
this happens randomly, the jump when checking the spindle face is worse.
the random jump still occurs when the tapers are tightened enough to get all rollers turning.
unsure about the front taper as there no way to view it.

[Stustoys]

Were the bearings not turning at the top with in the old ones as well?
Are you sure you have a very solid mount for your indicator?

How you fix it though...

If its undersize I guess it could be ground.......but at what cost?
Anyone feel like scraping?

Stuart

[lather]

Stuart,
it had the same problem on the original bearings, and in the same area, which is at the top and bottom of the bearing.
had over tightened the original bearings before pulling apart the headstock, was too tight at the point all the rollers turned.
thought it was the crap in the bearings causing it or the cheap Chinese bearings.

Edit,
the indicator is on a solid mount and doesn't rock.
had removed the bog and paint from the front of the headstock which has not been painted yet.
can't figure out why it was bogged as the front and rear surfaces of the headstock are machined flat.
the indicator also goes back to the same readings after the inconsistent jump.

[pipeclay]

If by some chance your bearing bore was oval there should of been a visable indication when you removed the cones.
If this is a concern you will have to either mic your bores ,use a telescopic gauage or inside calipers to check.
What sort of marks were on the cone when you removed it.
Do you have any idea on how much clearance you should have when the spindle is installed.

[Dave J]

I would measure the bore first, but I don't think my chuck would spin a revolution by hand, maybe a 1/4 from memory.

Dave

[shedhappens]

If the bore is not out of round then the bore for the bearing may not be in alignment with the other bore ? That would load up the bearing on the sides and leave the top and bottom rollers slightly loose.

If you have bog there ? Then someone may have repaired it ?
.......and.....not line bored it correctly ????????

john

[.RC.]

needed to over tighten the original tapers before all the rollers turned, too tight for normal running.
the new bearings seem to be the same, feels tight when turning the spindle, doubt the chuck would free spin 1/2 a rev when giving it a spin by hand.

still getting unusual reading on the run-out, thought i got lucky as the run-out was 0.003mm, it then jumped 0.01mm after 2 turns.
this happens randomly, the jump when checking the spindle face is worse.
the random jump still occurs when the tapers are tightened enough to get all rollers turning.
unsure about the front taper as there no way to view it.

I would not worry too much about that.... Seems good to me... Remember the bearings will not have 0 runout, and as they were normal grade they never had the high spot marked on them so you can line the front and rear bearings up..

[simonl]

If the bore is not out of round then the bore for the bearing may not be in alignment with the other bore ? That would load up the bearing on the sides and leave the top and bottom rollers slightly loose.

If you have bog there ? Then someone may have repaired it ?
.......and.....not line bored it correctly ????????

john

I think this would be the most likely scenario. If the two spindles bores were not well aligned and parallel then this would put uneven forces on the tapered bearings. It wouldn't need to be out by much.

The back and front of the headstock on my lathe are machined surfaces. I assumed this is because they use these surfaces as a datum to then machine the two bores for the spindle. I have never taken any measurements but I would suggest that the back and front of the headstock should (repeat should) very parallel which would then allow the bore on each side to be machined parallel to each other. Being in line is yet another issue again.

Would placing the headstock on a surface plate and setting a DI on the plate and taking relative readings around the bore seat show how parallel it is?

Perhaps there is a more appropriate method to do this?

Just thinking aloud here.....

CHeers,

Simon

[simonl]

Actually I was just thinking. Maybe they machine both spindle bearing mounts from one side? That would make it much easier to align the two.

I just don't know how they would machine the other end unless they had a special upside down boring head?

Or perhaps they they just bore the hole in the other side and then turn it over and use that hole to centrally locate where to machine the second bearing mount?

Love to know. Someone out there much know!

Simon

[Stustoys]

Hi Simon,
Have a look at the second last picture from this thread https://www.woodworkforums.com/f65/he...y-tour-154255/

Stuart

[pipeclay]

Wouldnt the usual practice be to line bore and face in the one setup.

[lather]

removed the spindle, gave the bearings a clean and reinstalled them.
measured using a test bar this time and had consistent results.
through each turn now the readings are moving up and down about 0.01mm several times during each rev, most likely due to not being precision bearings.
the rollers at the rear still have the same problem, though the spindle feels better and can be tightened up some more.
best guess is that the bearings somehow were contaminated, or need to be cleaned when new.

Checked the old cones, which only ran for 30 mins from new, and shows a wavy wear pattern on the rear cone.
the front cone has more wear on opposite sides.

wasn't concerned about the bog covering a defect as the surface underneath was O.K., only thought that it was a waste of time bogging the front as it was machined flat and made for a good surface for the magnetic base, which was rocky when bogged.
they could have spent time lining the gear positions correctly, so they don't run on only half the gear, and make sure the forks don't hit the gears when in the correct position.