Cincinnati 12-1/2 Tray Top Free-Spinning Handwheel
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  1. #1
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    Default Cincinnati 12-1/2 Tray Top Free-Spinning Handwheel

    Hi! Brand new to the heavy iron world (please bear with me) and hoping to start with a Cincinnati 12-1/2x48 tray top from a deceased friend. The only apparent issue is that the carriage is stuck up near the chuck--the handwheel only spins. I can see that it does slightly tweak the pinion but otherwise has no effect. If I pull the left lever, which the manual appears to say is the power feed selector lever (?), the handwheel locks up solid.

    I would think a sheared pin somewhere in the apron, but I'm confused because looking at the manual it appears the pinion is directly connected to the handwheel? Note the image in the manual does not appear to match my carriage very well. It don't think it could be the keyway since it will lock up with power feed engaged. In any case, a few questions:

    1) any educated guesses as to the issue I might be having?
    2) is the procedure to repair likely to be a mighty job?
    3) is there any way to manually move the carriage? I need to get it out of the way to move the lathe, preferably as far to the tailstock as possible.

    Thank you in advance for any assistance. And sorry about the picture rotations; my phone isn't a fan! I'll try to fix from a computer tomorrow.
    Attached Thumbnails Attached Thumbnails pxl_20210531_181908572.jpg   pxl_20210531_182001362.jpg   screenshot_20210531-203056.jpg   pxl_20210531_181845723.jpg   pxl_20210531_181824910.jpg  


  2. #2
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    pxl_20210531_181824910.jpg

    A guess would be this plunger takes rack pinion out of engagement with rack gear

  3. #3
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    That knob is an oil pump tor the carriage lube. Sorry, no help on the repair. Bob

  4. #4
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    Hard to see in the scan, but it's likely a key has sheared from feeding into a shoulder. I just performed the same fix on a PW Model C, the apron has to come off to access it unfortunately.

  5. #5
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    If you've already sorted our your issue, please disregard this reply. I only saw your post this morning. I believe your problem is a loose idler gear on the rack pinion shaft, a relatively easy fix, although the apron does need to come off.

    Your lathe apron does not match the exploded diagram you posted. Your lathe appears to be the "LE" model,the apron has separate levers for the longitudinal and cross feeds. The diagram you posted is from the earlier lathe with a push-pull rod to change between longitudinal and cross feed.

    I (hopefully) attached the exploded diagram from the LE apron (you can find it on Vintage Machinery's database).

    The handwheel is not directly connected to the pinion gear that engages the rack on the backside of the apron. The handwheel shaft (#10) terminates inside the apron. The pinion gear on the handwheel shaft engages an idler gear(#12)on the rack pinion shaft (#11). This second pinion gear is on the back side of the apron, and engages the rack.

    Possible causes of failure will be on either the handwheel pinion shaft (lost Woodruff key) or on the rack pinion shaft. When you engage the longitudinal feed, the handwheel locks up, which suggests the handwheel shaft is not the problem.

    The rack pinion gear is driven off the idler gear. When the power feeds are disengaged, the handwheel pinion gear engages the idler gear, which drives the rack pinion. If the idler gear (appears to be secured with a roll pin on your lathe) is spinning on the shaft, the rack pinion won't spin. When you engage the power feeds, the gear train is engaged from the worm gear through the apron to the handwheel, so the handwheel won't turn. If you powered up the lathe and engaged the power feed, the apron won't move, because again, that rack pinion is disengaged from the idler gear. The cross feed will likely work, though.

    I've got an apron from the older version on my bench. The first pic shows the feeds disengaged, the second pic shows the feeds engaged. Again, this is different from your lathe but may help show where the problems lie.

    le-apron-front-view-exploded.jpgtraytop-apron-feed-disengaged.jpgtraytop-apron-feed-engaged.jpg

  6. #6
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    I posted a rather wordy response, which probably complicated the problem. Basically, there are two pinion gears in play here. One is on the handwheel shaft, and terminates inside the apron. The second pinion is the rack pinion, it's the one you can see behind the apron, and which engages the rack gear.

    Your problem is probably the idler gear on the rack pinion shaft. It's secured with a roll pin on that version of the Tray Top lathe. Remove the apron, drive out the remnants of the sheared roll pin and replace. It will make perfect sense when you see it. Fortunately, that shaft is all the way to the top of the apron, and you won't need to disassemble the other shafts and gears to access it. While you're in there, blow some compressed air through the oil lines to make sure they aren't all clogged up with gung (which is likely).

  7. #7
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    Quote Originally Posted by "Mike" View Post
    Your problem is probably the idler gear on the rack pinion shaft.
    I kept incorrectly calling this gear an "idler" gear, which it's not. It transmits power from the handwheel to the rack pinion from either the handwheel or the power feed gears. I guess it's technically a "wheel", but I'll call it an intermediate gear. Anyway, that's my 3am geek needing to correct something that probably doesn't matter to anyone but me, lol.

  8. #8
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    Whatever the issue the problem is inside the apron. You will need to take the apron off to fix so you might as well take the apron off to identify the issue.

    Vlad


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