Atlas 618 Backgear Issue

[JRT]

Here's a video of my issue. When the pin is pulled out from the Bull Gear and the Back Gear is engaged, the chuck absolutely will not spin. Any ideas? I think I'm missing something obvious here, I hope I am anyways.

 

[Canuck75]

Here's a video of my issue. When the pin is pulled out from the Bull Gear and the Back Gear is engaged, the chuck absolutely will not spin. Any ideas? I think I'm missing something obvious here, I hope I am anyways.

What I don't see is the V-pulleys and the bull gear moving separately when the pin is disengaged - are they really free from each other? Check that it is actually happening or is the V-pulley frozen on the spindle?
Just a thought.

 

[markba633csi]

Yes, you should be able to turn the cone pulley separately from the bull gear with your fingers (power off of course)
Did someone tighten the infamous cone pulley setscrew? That setscrew is for oiling access only- it shouldn't be tight.
If tightened down it would lock everything up
The factory should have used a rubber plug or a cork for that hole- it would have caused a lot less confusion

 

[JRT]

What I don't see is the V-pulleys and the bull gear moving separately when the pin is disengaged - are they really free from each other? Check that it is actually happening or is the V-pulley frozen on the spindle?
Just a thought.

Good point, I think the cone shaped pulley is held down by a set screw. Is that not correct?

Yes, you should be able to turn the cone pulley separately from the bull gear with your fingers (power off of course)
Did someone tighten the infamous cone pulley setscrew? That setscrew is for oiling only- it shouldn't be tight.
If tightened down it would lock everything up

Yes, I did as it was that way when I awuired it! I’ll undo that and see where I stand… I am missing the collar that goes between the teeth end of that cone pulley and the front, inner dust cover of the rear bearing so it may not work… guess I need to source one of those.

 

[markba633csi]

The setscrew causes a lot of grief for new Atlas owners- it's massively mis-understood, often because the operation of the backgears is mis-understood.

Sounds to me the previous owner was trying to run the machine with parts missing so they cranked down the cone pulley screw to give some sort of half-arsed preload on the front bearing (Horrors!) which of course means the backgears could not be used.

 

[markba633csi]

Can you post a close-up picture of your machine, especially the headstock? There may be other issues we could point out
(might as well fix as much as you can, right?)

 

[JRT]

Can you post a close-up picture of your machine, especially the headstock? There may be other issues we could point out
(might as well fix as much as you can, right?)

Yes, absolutely I will in a few…

 

[JRT]

Here’s my headstock. Any help with missing parts would be so great!

 

[JRT]

Okay, I just found the spacer (M6-78) on ebay that goes against the outter bearing dust cover on the gear end of the spindle. It looks like I already have it there in the pictures but it's definitely not the correct spacer as it has two keyways in it.

I also found and ordered a spacer that is said to go on the spindle (no part number was associated with it) in hopes of it fitting the gap between the inner bearing dust cover on the gear end of the headstock and the cone pulley. Fingers are all crossed!

Does anyone happen to have the measurement of this spacer in case this one doesn't fit? I may be able to find something at the local hardware store.

Thanks guys! -John

 

[markba633csi]

I can measure mine- give me a few, I'll be back
OK the width looks like 0.20 inch and the OD is 1.125 inch
The diameter of the spindle there and for the cone pulley is 0.787 inch
then it narrows down at the left hand end for the bearing at 0.750 inch