Thanks all for the suggestions and information. Apologies if this is post is too long as I try to respond to everyone in turn...:
From the OP it doesn't sound like trashed bearing(s) or shaft worn loose. I keep thinking, if it's sliding in and out there has to be something missing; a spacer/shim/washer-looking thingy or the big clip that holds the grooved bearing?
I also wondered if there was something missing, but I don't
think that there is. I'm not certain that I totally understand what's supposed to retain everything, but I don't see what
could be missing. The circlip was present, as was the spacer/shim/washer-looking thingy, and the cap that screws over that.
Your description of both bearings being grooved makes me wonder about it being rebuilt before. Only one of the two is grooved in my limited experience.
I guess I wasn't clear: while there are two bearings with the same part number (New Departure 3209), only one of the bearings is grooved. At first I thought that it may have been rebuilt before, but based on more recent comments on this thread, now I'm not sure.
The gif sure does make it look like it is a proper slip fit. If miraculously the bearings are still good you could loctite the shaft into the bearings.
Again, if they are still serviceable glue the shaft in with loctite and move on. If the fit is very smooth as your gif makes it look, then use Loctite 290 which will wick around the circumference of the assembled parts.
I had this same thought, though I don't have prior experience with bearing retainer. Thanks for suggesting a particular type. I'm a little hesitant to use bearing retainer to secure the output shaft to the old bearings in case they're no good, as I don't know how I would get the bearings off at that point. If I go this route (to salvage the shaft), I think I will use new 3602 bearings.
The bearings spacers are so precise they could have held the bearings preloaded even while the shaft was loose.
I'm not quite sure that I follow. The bearings that were in there are deep groove, so they shouldn't get an axial preload, right?
As a former technical columnist author your posts have impressive clarity.
Thank you, I appreciate the compliment!
One last thing, based on your trepidation, do you have the parts diagrams?
The only parts diagram that I have is what I could find in
this manual:
I didn't realize that there were drawings available for these lathes until you said this, which explains how I see so many other users posting detailed part numbers (i.e., EExxxx). I have not been able to locate a detailed manual for this lathe in our shop. When I contact Monarch I'll see what they'd charge for this.
I am home now and checked my parts drawing. The bearings are not angular contact. The are normal ballbearings with a spacer on both the inner and out race. Outer spacer so the assembly can be pressed into the casting and inner spacer so they can be pressed off the shaft through the holes in the gear.
Interesting--I guess that makes your and my lathes in the minority? Perhaps Monarch switched to angular contact later. See, for example,
this comment from
this thread:
The bearings in mine are, in fact, 6209s - standard ball bearings. Talking to Scott at Monarch he says that they should be angular contact bearings - 7209s.
Before I saw your post, I started to wonder if maybe the bearings in my gearbox were original, based on the parts photo I attached above:
Before, I had suspected that the reason the shaft measured slightly smaller than the bearing ID was that the shaft spun in an original set of angular contact bearings, and were then replaced with the ND 3602's as a substitute. It was theorized in
this thread that the reason for DaveC's shaft coming loose within the bearing was due to fretting, which is something I didn't know about previously. Taking a closer look at my gearbox, the bearing closer to the output side of the gearbox and the shaft at that same point show a surface finish that could be this?
FWIW, the square-dial machines used two slightly different gearboxes, but even so, most internal parts are the same.
Whether your one is round-dial or square, AFAIK, all the MG-era 10EE with "large-frame" Reliance 3 HP-rated DC 690/2400 RPM final-drive motor, (single-keyway motor shaft, not splined), are the same as to which bearings & c. fit and whether the input bearing shares duty with motor output shaft or not.
Do keep in mind in your research and parts sourcing though, that later gearboxes may not be 100% identical as to internal parts to your one.
Thanks for pointing out those differences. I did notice that
DaveC's gearbox had a splined output shaft whereas mine has a slot for a key. The output shaft of the motor in my unit is keyed and not splined like you described. I'm not sure what you mean by "whether the input bearing shares duty with motor output shaft or not" though? There was not a bearing in the rear of the housing (at the gearbox input, which is the motor shaft), so the bearing in the motor frame is all there was to support the motor output shaft / gearbox input shaft.
Also, I realized that the plate which seals the end of the output shaft had been removed some years prior. I didn't know until yesterday that there was supposed to be something sealing the end of the output shaft, but it's fairly obvious in retrospect. (The motor output shaft slides inside of the output shaft and fits loosely; oil can leak around the motor output shaft and out of the center of the gearbox output shaft if this plate is not in place.) At first, I suspected that this may have explained why there was no oil in the gearbox, but I no longer suspect that the removal of this plate had anything to do with that: I believe that the bottom of the output shaft ID is above the oil level, and I think that this plate was only removed to facilitate removal of the sheaves. I did find the plate in a box of parts, so I at least don't have to get or make one of these.
One last thing: the taper pins that I found were a little suspicious, suggesting possible prior rebuild. They were of the sort that are threaded on one end, but the threads were quite buggered. The other really odd thing is that they had nuts installed on them--I can't imagine Monarch installing tapered pins with nuts that could vibrate off inside of the gearbox and possibly wreck something. I also am not sure that I've seen photos of any other gearboxes on these forums that have shown threaded tapered pins, and the parts diagram that I have doesn't show threads on these, either.
It has been a long time since I converted my 10EE to VFD, but when I was running the M/G with backgear like yours, my gearbox had bad seals (aka 'automatic belt oiler')...
From what I recall, lateral play in that shaft had no significance in operation, performance, or longetivity, and IIRC, my gearbox bearings were slip-fit on the shaft as well.
Realize that any component subject to thermal change, must accomodate expansion... and likewise, in design, it is not wise to try to captivate or otherwise enforce precision upon some component, where captivity or precision is not necessary... you don't want thermal expansion to cause something to interfere or deflect, and cause problems elsewhere.
SO... while slop in that component may be initially discomforting, it may be inconsequential, or even moreso, desireable.
I'm not entirely certain that I agree with this sentiment, as lateral play of the output shaft means that, when the gearbox is in its "low" range, the output shaft gear might not be meshing fully with the gear from the shaft above. When the gearbox is in "high" (1:1) and the dogs are engaged, the shift fork will apply pressure on the output shaft (by way of the dog gear, I'll call it), limiting the shaft axial travel. But, in any case, the shaft can rotate freely in the bearings, which seem to primarily want to stay stationary and not rotate. If there's not adequate lubrication between the shaft and the bearings (which, as the gearbox is splash lubricated, seems likely), I would expect the shaft OD and bearing ID to wear where they rub, which seems undesirable. At this point, the 3602s would seem better replaced with bronze bushings?
FWIW... last time I checked, you can CALL Monarch, with your machine's serial number, and they can look up the original sale document, pull the appropriate documents, and make you a complete copy of the original manual set... you will find it very useful, as then you'll be able to tell what is original, and what has been changed.
They can also source parts for most Monarch machines... they did for me.
Thanks for the suggestion. I intend on reaching out to them some time this week.