How to fix back gear separating from belt pulleys on Atlas 618

[skcncx]

How do I fix or what should I be looking for when my Atlas 618 back gear (the larger headstock gear) is separating from the v-belt pulleys and therefore the headstock stops spinning?

I attached two pics... a good and a bad, it goes from good to bad during use... I can slide it back, but it just keeps separating from the pulleys.

There appears to be two set screws in this larger gear, one over the pin that is pulled when you engage the back gear and one other. I think I'm missing the second one, I'll have to figure what the the size and thread is and source that. Not sure when I lost it. The one over the pin for the back gear engagement has a spring under it... so I imagine that it's not intended to be tightened down and possibly just put tension on the pin to keep it in place.

I just swapped out my standard 1725 RPM constant speed motor for a Consew CSM1000 variable speed motor, mended a new urethane v-belt and then started noticing the larger toothed gear in my headstock was separating from my v-belt pulleys in the headstock... I don't believe these changes are related but just coincidental.

Any thoughts/suggestion would be helpful!

Off topic... I did read the pinned thread on the set screw (or rather, it's not a set screw) on the v-pulleys, mine is in the bottom part of the second smallest v-pulley... I guess that and oiler area, looked like a set screw! Still learning the ins-outs of this thing and want to make sure I'm using and maintaining it properly.

 

[markba633csi]

It looks like the bull gear that's moving- it shouldn't be. Figure out the setscrew issue and that should do it
The screw hole in the step pulley is just for oiling- should not be tightened down to where it bears on the spindle
-M

 

[skcncx]

It looks like the bull gear that's moving- it shouldn't be. Figure out the setscrew issue and that should do it
The screw hole in the step pulley is just for oiling- should not be tightened down to where it bears on the spindle
-M

Thanks. "bull/back gear"... now I now what that thing is called. Looking at the exploded parts diagram it's an 8-32 set screw. Love it when I can easily source this from the local hardware store.

Just seemed odd because that set screw w/spring that is right over the pin that is pulled in/out when you engage the back gear setup, had no affect, my guess is that other one will be the one that locks it in place and that is the one I'm missing.

 

[Soggy618]

The "deep" set screw is likely the problem, but when I got mine home, the set screw on the pulley was screwed down tight and when I
first tried the back gear, the backgear and the pulley would separate much like this. Be sure the oil set screw is backed out enough for
the pulley to spin freely on the spindle, just to be sure.

 

[skcncx]

The "deep" set screw is likely the problem, but when I got mine home, the set screw on the pulley was screwed down tight and when I
first tried the back gear, the backgear and the pulley would separate much like this. Be sure the oil set screw is backed out enough for
the pulley to spin freely on the spindle, just to be sure.

Thanks, I'll be getting the deep set screw today and try that... likely is the issue. The shallow, set screw w/spring behind it for the engagement pin, I'll back that out... cause obviously when it was tight, the pin could not be pulled in and out.

In my effort to trouble shoot and resolve the issue, I was screwing the pulley screw tight... now I know it shouldn't be (and I'll oil it in the process). I just (wrongly) assumed, if there's a screw there, tighten it down .

 

[markba633csi]

That darn oil screw causes more confusion and grief than just about anything else on an Atlas/Craftsman
You're not the first and won't be the last

 

[skcncx]

That darn oil screw causes more confusion and grief than just about anything else on an Atlas/Craftsman
You're not the first and won't be the last

I need to go through the manual again and see all the proper oil points. I have just been putting VELOCITE OIL NO. 10 in the two headstock oiler caps, couple drops each use and VACTRA OIL NO.2 a bit thicker on the ways... Maybe a couple drops of the vactra oil no. 2 on the threading gears as well.

 

[RJSakowski]

AFAIK, the second set screw on the bull gear does nothing. I believe that your problem is caused by excessive axial play in the bull gear/pulley assembly. There is a spacer with a set screw to the left of the pulley which controls axial play (120 and 221, P/N M6-89 and 127555). Loosen the set screw and slide the spacer to the right to take up excessive axial play and tighten the set screw. If the problem reoccurs, you may want to add a shim washer to the spindle to prevent the spacer from sliding back.

 

[skcncx]

AFAIK, the second set screw on the bull gear does nothing. I believe that your problem is caused by excessive axial play in the bull gear/pulley assembly. There is a spacer with a set screw to the left of the pulley which controls axial play (120 and 221, P/N M6-89 and 127555). Loosen the set screw and slide the spacer to the right to take up excessive axial play and tighten the set screw. If the problem reoccurs, you may want to add a shim washer to the spindle to prevent the spacer from sliding back.

Thanks... I'll look out for that. The pulley assembly part #121, that has the smaller gear affixed to it on the left (as if looking from the front) does not appear to shift at all... it does appear the larger toothed gear on the right part #122, as seen in my pics moves to the right. This larger (bull gear), really needs to be butted up next to the pulley/gear (part #121) since if it slides to the right at all (my issue) it get's close to interfering with the indexing pin and moves far enough from the pulleys that the chuck won't spin. I do agree that the extra set screw may do nothing, but I have one now and will at least try it out and look at that spacer you are calling out.... just seems strange I have been using it on and off for a few weeks and seemingly out of the blue this issue shows up when I really haven't done anything to those parts.... other than wrap a new belt around the pulleys (did not take apart the headstock... just melted a urethane v belt.

I'll certainly report back as to what fixes it.

 

[skcncx]

Well, time will tell, the the deeper set screw on the bull gear was actually in there, of course I figure that out after I went out and got one...and it did seem relatively tight... so all I did was back it out and re-tighten it and with a little use so far seems to resolve my issue... hopefully that's it.