What are these next to the Back Gear?

[Darla]

I'm restoring an atlas-craftsman 618, unknown model # (id plate missing). I've gotten the spindle out, and notice two odd pieces, like washers, between the back gear and the dust cover. This would be toward the right side of the spindle, but in these from-the-back photos, they're to the left of the back gear. The exploded diagrams I have seen don't show anything in that space. Was mine put in as a spacer? For some other function? On top of that, they appear to be broken. Has anyone seen this kind of thing, or have ideas? - Thanks.

 

[francist]

I don't see anything on my exploded views either -- there is a spacer M6-89 on spindle but you appear to have that already. Maybe previous owner put in a couple additional ones to try to stop the back gear from walking away from the pulley assembly? Mine does this occasionally if the set screw loosens up.

-frank

 

[itsme_Bernie]

Quick fact here- just to help you find what you need. That big gear, on the spindle, is a "bull" gear. The backgear engages with it, yes, just so you know.

Now. What the heck are those broken looking parts? I'll go look it up in my digital library...


Bernie

 

[francist]

Not to be a troublemaker, but in all fairness to Darla the exploded view provided by Crafstman for the 618 identifies part #M6-241 (the bull gear) as "Back Gear".

-frank

 

[wa5cab]

"Bull gear" is the colloquial term for the larger of the two spindle gears in a back gear equipped lathe (not all are). I.e., the term is actually in-crowd jargon and we use it to show that we are "in". :whistle:

You see the term occasionally in the text in manuals and text books, and quite often in messages but I can't recall ever having seen it in the Description column of any parts list.

- - - Updated - - -

Back to the weird pieces that Darla found in his machine, my first guess now that I've seen photos is that they are the remains of a thrust bearing. For which there is no conceivable need in the location in which they were found. The set screw in the large spindle gear (AKA bull gear) locks the gear with the proper clearance between it and the spindle cone pulley.

Robert D.

 

[Marco Bernardini]

Wifey's suggestion¹ is the broken part could have a tooth, or something similar, engaging the stud on the back gear for some unknown reason.
This until someone abused of it, breaking it.

___

¹ Wifey worked for 18 yrs in her dad's garage, mainly on motorbikes and Piaggio Ape (this: https://en.wikipedia.org/wiki/Piaggio_Ape), and she knows gears far better than me.

 

[Darla]

Re: What are these next to the Back Gear? and what about the Bushings?

Thank you all for weighing in on the odd and presumably unnecessary neighbor to my Back/Bull Gear. I shall leave it out when I reassemble. But I realize I need more information first.
1. Shall I try to remove the bushings from the cone pulley? (identified in exploded diagram as 2140-10 'pulley and gear with bushings', and bushings identified as m6-258). They are still in there and I can't easily take them out. Will try if urged. They are scored and show wear but appear to be otherwise in good shape. see photo.

2. The set screw in the cone pulley partially contacts one of the bushings. (if you peer into the set screw's hole you see the bushing, covering 60% of the space, and the edge of the bushing, and dents where set screw has been pressing) Is this how it's supposed to be?

3. I'd welcome tips for reassembling the spindle assembly - for instance, Robert said "The set screw in the large spindle gear (AKA bull gear) locks the gear with the proper clearance between it and the spindle cone pulley." This makes me wonder what that clearance might be... also, shall I lubricate pieces during reassembly or later? What else?

 

[wa5cab]

Darla,

1) Slide the cone pulley back on the spindle up to its nominal running position and then try to determine how much running clearance there is between the bushings and the spindle. Should be roughly 0.002" or less. If much more, order replacement bushings from Clausing and replace them.

2) On the apparent set screw in the cone pulley, read the sticky post at the top of this forum. It isn't a set screw, it is an oil plug. If some previous owner was dumb enough to run the oil plug all the way through the pulley, the only way that I can think of to repair the damage and prevent it happening again is to stud-lock a specially prepared #6-32 Helicoil in the bottom of the hole.

3) Running clearance between the pulley when pushed onto the spindle as far as it will go and the gear should be on the order of 0.002"-0.005". Try setting it to that by slipping a feeler gauge or a strip of shim stock into the gap, pressing the gear lightly against it, and tightening the set screw in the gear. Then remove the spacer and confirm that the pulley spins freely.

Lightly oil all parts during assembly with SAE 10. Do not use grease.


Also, I thought that I had asked whether or not there are any badges or decals on the headstock, carriage or front of the bed. But I can't find it, and so ask again.

Robert D