Back Gear Disengaging On It's Own

[paul s]

On a 101.07403.

The back gear shaft has a spot where it binds with the eccentrics slightly. I have the two disc springs installed and have tried moving the collars to get more tension, but the gears are still kicking out. I'm guessing that the two eccentrics are pinned in place and there's no provision for creating clearance between them and the shaft that the gears ride on? Could also be that one of the bushings is protruding slightly.

 

[wa5cab]

I don't have a 10" or early 12" to look at but basically the eccentrics that move the gears in the horizontal plane must be able to "break over-center" in order for the engaged position to be stable. If the gear teeth bottom out before the eccentric has brought them as close as they will get and then started taking them back apart, then you need to add 10-261 shims to the shim packs between the 10-245L and 10-245R Brackets. The later manual says that they were available in 0.002" and 0.003". If, however, the 10-254 Handle strikes the 10-245R Bracket before the gear teeth bottom out, the hole for the Handle in the 10-251 Eccentric may have been mis-drilled.

The two 10-147 wave washers are there to keep the parts from rattling, not to keep the back gears engaged.

 

[paul s]

The teeth aren't even close to bottoming out. And that's even after I removed the shims, which measured 0.009", one on each side. Even without the shims, the back gears still kick out. I did move the left side gear further over towards the center, as it may have been rubbing against the eccentric, still kicking out.

I did replace one of the gears on the back gear shaft - I bought an entire back gear assembly off ebay just for the gear. It is possible that I mixed and matched parts - it was so long ago, that I can't really remember now. The spare brackets have a 10-24 tapped hole in the upper side of each casting, which is not present on the brackets that are on there, not sure what that's for.

 

[wa5cab]

Well, I am pretty sure that the thing is supposed to work as I described . I can't think of any other way that it could work. With the parts that you have, all that I can suggest is to check whether or not the other pair of 10-245L/R Brackets would mount the 10-250 Shaft closer to the spindle. perhaps some with a 3/8 bed 12" might chime in on the subject.

 

[Lastwagen]

I am restoring a Craftsman 12” lathe (101.07403 , 3/8” bed ways) and it had a broken back gear mount. I found what looked like a good replacements for it so I bought it.

But when I got it I compared it to the broken mount and it was a slightly different size (mounting distance), so I suspect there was a design change at some point. I believe my lathe is a ‘44 vintage.

So I could see that if you mix parts, then your eccentric movement may be too far for a proper engagement.

I’m still looking for a replacement ( hard to find someone selling just a single part, usually it’s the complete back gear setup).


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[Lastwagen]

.........The spare brackets have a 10-24 tapped hole in the upper side of each casting, which is not present on the brackets that are on there, not sure what that's for.

I know what the tapped holes are for; there are two gear guards, a right and a left, that are secured at the back into those holes, and at the front of the headstock at two thru holes ( each guard has a tapped hole at the front).


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[wa5cab]

But I have been through all of the 10" and 3/8" bed 12" parts lists and the only part number right back gear bracket part number that I find is 10-245R. That is from 101.07381 through 101.27440 plus the early and late 10F's. That includes models that originally shipped with the individual gear guards and ones that didn't. The next time that I call Clausing, I will try to remember to ask whether they can send scans of either or both of the back gear brackets. I agree that the #10-24 tapped holes are for the rear of the individual gear guards. But it would appear that unlike all other known cases, they modified the brackets without changing the part numbers. Sometimes, there are changes made that are recorded on the drawings.

Does anyone own a 10" or pre-1957 12" where they can tell that moving the back gear lever through its range results in the back gears moving closer t- the spindle gears and then back slightly away?

 

[Lastwagen]

I checked on my Craftsman 12” (101.07403) that the full cycle, stop-to-stop, results in singular movements; in or out. The end of travel to engage had no hint of movement to disengage. I hope that helps your question.


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[wa5cab]

Is there any significant difference between the two 10-245R's that you have other than if you run a temporary shaft the same diameter as the 10-251 Eccentric through both side by side, the mounting surface of the one that you bought as a replacement sticks out farther than the matching surface of the original broken one? Disregard any #10-24 tapped hole in either one.

I am almost convinced that the way in which the back gear engagement should operate is that as you move the lever from disengaged to engaged, the teeth of each pair of gears should be completely clear of each other when fully disengaged and as you move the lever towards engaged, the gear teeth should mesh fully and then back out slightly. If that doesn't happen, the engaged position will be unstable and will have a tendency to disengage when running.

 

[Lastwagen]

Is there any significant difference between the two 10-245R's that you have .......

Here is a photo that will make clear what I have as the difference.

The Countershaft Tension Lock (L3-108) will not install with that particular Back Gear Bracket (L4-245L). My guess is that the Back Gear Assy I purchased was for a similar lathe with a different tensioner mechanism. The other parts are identical except that bracket.


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