SB 9 Back Gear will not stay engaged

RVbeemer said:
Mmmm. I'll go play with mine and see what happens. Do you remember if you went tighter or looser?
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If I recall correctly I went looser so that there was less engagement and the lever could pass over center.
 
These are the only bolts I adjusted.
If I recall correctly, the slotted adjuster is for the engagement and the regular hex head locks the eccentric in place.
If you only have the one maybe it does double duty?
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Manual Mac said:
Will this help? It’s parts list for horizontal & underdrive 9” models fron June 15 1957.
The toolmaker or workshop models. Not the Junior (or heavy 9) which was discontinued in late 30’s or in the 40’s.
rvbeemer your lathe is not a junior or heavy 9.
it is an early workshop or toolmaker From the ’30’s. It has top spindle oilers.
also, to convert an early C like yours (there was not an A, B, or C model in the early ones) you would need a frame as well as the gearbox, as the frame did not have the relieved frame that the later A B or C had.
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Yeah, that looks like mine but there is no hole for #'s 19, 20, 21.
 
DavidR8 said:
These are the only bolts I adjusted.
If I recall correctly, the slotted adjuster is for the engagement and the regular hex head locks the eccentric in place.
If you only have the one maybe it does double duty?
87636271ed04181f2c77f7265543b85a.jpg

4fe26a7aeac2017c1da4ec295c0d46fb.jpg
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David, I see you have two bolts, one on each end. The restoration manual says "The slotted screw is for the gear mesh adjustment and the square head bolt is for the eccentric adjustment." I don't have the square head bolt or hole. 1935 model
 
RVbeemer said:
David, I see you have two bolts, one on each end. The restoration manual says "The slotted screw is for the gear mesh adjustment and the square head bolt is for the eccentric adjustment." I don't have the square head bolt or hole. 1935 model
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Maybe the one bolt on yours does both functions?
 
I know the nut is just a lock nut and when I screw the slotted screw in it pushes the gears apart and turning it counterclockwise, it lets them close up. Not saying you are wrong, just can't see where that would put any tension on the eccentric. I think I will go out and back it off and see if the lever pulls further in.
 
The workshop models did not have the parts he is looking for.......
 
Thanks for everyone trying to help! I was hoping someone with a lathe like mine could chime in and show what they have.
I did try to adjust the gear mesh screw but the best I could get was about 20 seconds before it would kick out. I still wonder about that hole with a spring in it. There has to be a reason for it.
 
A lot of these use "over-center" locking.

The handle rotates an eccentric that causes the shaft to get closer and farther away.

As you rotate it and see that it gets to the closest point then go just past that it opens up again.

There should be a screw someplace that is what adjusts where it stops rotating, usually just over-center.

Natural forces then will try to push the shaft against the screw stop.

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