Atlas 6 MK2 direct drive won't stay engaged

[BillPDX]

Hi. Just purchased an Atlas 6 and the direct drive coupling won't stay engaged with the headstock pulley assembly. Looks and feels like the coupling isn't fully engaging with the headstock pulley assembly, so it pops out immediately on startup. The headstock pulley assembly has some movement on the drive shaft, like it's missing a spacer or something to keep the headstock closer to the drive coupling.

I've reviewed the parts schematic in the owners manual and I don't see any missing pieces.

Thanks everyone

Bill

 

[matthewsx]

Hi. Just purchased an Atlas 6 and the direct drive coupling won't stay engaged with the headstock pulley assembly. Looks and feels like the coupling isn't fully engaging with the headstock pulley assembly, so it pops out immediately on startup. The headstock pulley assembly has some movement on the drive shaft, like it's missing a spacer or something to keep the headstock closer to the drive coupling.

I've reviewed the parts schematic in the owners manual and I don't see any missing pieces.

Thanks everyone

Bill

Hi and welcome.

I don’t have a specific fix for you but I’d did have a small Craftsman lathe that may be similar. Is the problem when you pull out the piece at the end of the spindle?

Can you post some pictures?

John

 

[markba633csi]

I have a MK2/3950. There should be a ball and spring in the collar to keep it engaged. You'll have to pull off the collar and check.
If the dogs that engage the collar to the pulley are quite worn I can see that might cause it to jump out

 

[RJSakowski]

I have an Atlas/Craftsman 6x18 which should be similar to your lathe. There is a pin on the side of the bull gear which locks it to the drive pulley. There is also a set screw in the gear face which will lock the drive pin in place, either out for back gear operation or in for direct drive. I don't recall if there is a spring and ball under the screw but if you tighten the set screw, you should be able to keep the pin engaged. You will have to loosen the set screw to switch between direct drive and back gear operation.

The drive pulley is cast aluminum or Zamak and they tend to wear with the years. The socket that the pin engages can develop a ramp, camming out the pin under heavy loads. If the above fix doesn't work, you may be looking a to a disassembly and removal of the pulley for repair or replacement.

 

[markba633csi]

The MK2 is quite different from the older 6" as far as the spindle drive- It's actually kinda nifty
but it does have a couple wear points, the collar mech being one of them

 

[BillPDX]

Thanks everyone for replies. Here are some pictures and more information.

I've removed the coupling (collar), along with the pulley to inspect what's going on. The spring and ball are in place and move freely and I can slide the collar on the drive shaft and feel the ball seat into the groves cut in the drive shaft. There are two groves, engaged, not engaged. I'm noticing my headstock pully which the coupling locks into for direct drive can slide on the drive shaft. When it slides in the direction of the chuck, the coupling only partially engages and slips free on startup. Wondering if my lathe is missing a spacer or bushing on the drive shaft which would position the pulley closer to the coupling and allow it to stay engaged? The dogs on the collar look to be in good shape.

Could the alignment of the drive belt be the problem? I'm noticing the belt pulls the pulley towards the chuck, into the "No Gap" position (see pic). I could re-align the drive motor so the belt keeps the pully away from the chuck in the position of the picture showing the "Gap", this would allow the coupling to have better engagement.

Thanks for all your help.

Bill

 

[matthewsx]

Definitely get the drive belt aligned, easy to do and needs to be done anyway.

John

 

[BillPDX]

After aligning the drive belt, direct drive engages much better, but is still not perfect. Thanks everyone for the help and suggestions. I'll post a pic or two, once the machine is all cleaned up and back together.

Bill

 

[markba633csi]

The excessive gap is from wear- I think you could put a washer in there (what was I saying about wear points?)
The alternate location for a washer could be on the outboard end just behind the second snap ring- easier to do perhaps
As a last resort you could put a stronger spring in the collar under the ball
Is yours missing the idler pulley? Probably not essential but it helps when changing belt position

 

[BillPDX]

Thanks for the suggestions, I like the idea of using a washer to minimize the side to side movement. The washer will also help keep direct drive engaged. And yes I have the idler pulley installed.

Just noticed the 3-20-1978 date on the housing behind the gears.

Thanks