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Back Gear Shaft Craftsman 101-28990 -12 x 36 inch.

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Keith A

Registered Member
Aug 5, 2017
I ordered a shaft and an eccentric from Clausing for my back gears due to the one in the lathe I just purchased looking a bit like Elmer Fudd's gun after Bugs put his fingers in the barrels and it was fired.

The problem with the new parts is that there appears to be a hole missing where a pin is supposed to go, according to the exploded diagram. (See Back Gears Below) According to a tech at Clausing, they changed the design to eliminate the pin. He couldnt figure why they did that and I am not quite sure why either. I was wondering first if anyone knew if or how the design might work without the pin?

Anyway according to the exploded view there are two eccentrics: No. 33 and No. 63. Each has a hole and a pin (Nos 34 and 62 respectively on the diagram) that is supposed to engage shaft No. 61. A lever clamps on to eccentric No. 63 which rotates the eccentrics and correspondingly moves the back gears out of range of the spindle gears. All seems to figure and would move both eccentrics equally if there were pins or something to lock the shaft in each eccentric.

I can only see that without the pin for eccentric No. 62 the shaft will be free to spin inside the eccentric and only when it binds from being cocked would it tend to spin the other eccentric. This might lead to partial or no disengagement and potentially broken teeth. The Clausing guy is attempting to find the old drawings; he said they may not exist.

So I figured I would ask here. If anyone has run into this issue or the off chance that you might have a diagram showing where this shaft and eccentric is to be drilled for the front pin.

My original shaft looks and eccentric looks like it was drilled in the machine in some haphazard attempt to get the eccentrics to rotate together. The No. 62 eccentric has about 6 holes in it and one time it appears someone tapped it in order to potentially have a set screw engage the shaft.


Last edited:


HM Shop Superintendent
Staff member
H-M Supporter - Sustaining Member
Aug 8, 2011

I don't know if anyone has offered you any help on this or not. Not sure I can but I'll try.

Looks to me that a rat got ahold of it and made a mess trying to fix it the first time. Be amaze how often I run into this on machines I've worked on.

One of the things I've run into also, is the unwritten documentation on how it went together at the factory. And it looks like your situation is no exception.
If it was me, I would either make a new eccentric bushing and shaft or buy these new from Clausing. And if those two parts are supposed to be new from the factory, send them back and get your money back! They shouldn't have all of those butchard up holes in them! Sounds like to me that someone else returned them after butchering them up because they could not get the alignment right, and Clausing just put them back on the shelf instead of scrapping them and making the buyer pay for them. Seen this happen, too in my past. Most machinery assembly generally has instructions on aligning the two pieces, drilling and reaming the pin hole, and installing the pin. For the size of the two pieces, a number 1 or 2 tapered pin should be all it needs for assembly.

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