Making a Hybrid Pitman

Funny how you can go for ages and not have a particular problem, then it will pop up in a couple of places. I recently obtained some parts for a Singer industrial treadle frame, almost enough to assemble a complete one. Only problem was that the treadle platform pedal was for a wooden pitman while the drive wheel was for a metal, ball bearing pitman. There were some other problems, but that was the big one.

While I was contemplating how to cobble up a adaptor pitman rod, Bernie Pokorski had apparently been facing the same problem and he came up with a very nice, clean solution that is not beyond the range of most home shops. Bernie was kind enough to provide instructions and photos.


In thinking it over, I thought that I should post a description of the methods that I used to create the hybrid pitman for my Singer 31-20. Here it is:

Basically,the 16" lower drive wheel that I acquired was designed for a metal pitman. It has the female-threaded ball bearing assembly on it's axle., and it's correct pitman would have had male threads on one end, and the lower ball/socket joint at connection to the treadle. In any case, the wheel and axle combo came without it's pitman .
My 31-20's original stand has a treadle with the 1/2" diameter solid cast iron 'post' sticking out horizontally and to the right to accept a wooden pitman.

I had an extra metal pitman laying around, so I originally cobbled together a two-piece metal pitman that had the proper male threads at it's upper end, and a metal loop that fit the treadle's post a bit sloppy. It was a temporary solution at best, as it was somewhat unsightly and it made for a noisy treadle: clank, clank.......

In the meantime I kept thinking about it over time. What I eventually came up with is this hybrid pitman. The pitman's required length for the 31-20 is 12-1/4" from the end of the male threads to the center of the 1/2" hole for the treadle's post.

I cut the upper (threaded) portion of the temporary two-piece 'Rube Goldberg' metal pitman at 9-1/4" long, and I threaded the lower end of it with a 1/4-20 NC die, giving it two inches of threads.. (the metal pitman was the correct diameter to readily accept the 14-20 NC die).

Then, I cut a 1/2" X 1" piece of oak down to 5" long. I bored a 9/16" hole 1-1/8" in from one end of the piece of oak , on it's one-inch side. Then, I drilled a 1/4" hole down through the top dead center of the piece of oak to intersect with the 9/16" bore at a 90 degree angle. Once that was done, I installed a 1/4-20 NC siamesed nut/serrated washer onto the newly-cut threads.

I placed a 1/4-20 NC square nut in the 9/16" bore, and threaded the metal pitman down through the square nut, effectively joining the metal and wood components of the hybrid pitman. The siamesed nut washer was then tightened down against the top of the oak. I cut a few extra threads on the metal portion of the hybrid pitman to allow for fine-tuning it's overall length, if needed.

All that was left to do at that point was to bore the 1/2" hole into the lower portion of the oak to accept the post on the treadle.

Regards, Bernie....A Little Bit South of Grass Valley, CA
'Son of a Singer Man'


Here are the pix to accompany Bernie's explanation:



Piece of oak with holes drilled... botton hole (rounded end) is for the treadle platform. Steel rod is cut to length and threaded on both ends. Nut will go into upper hole to receive the threaded rod.


Note hole in wood piece to receive the end of the treaded rod.




Rod inserted into wood piece...



Showing rod, with lock nut on top of wood piece, ready to be screwed into the nut in the upper hole. This will lock the threaded rod to the wood adaptor piece and also provides some length adjustment.



And here is the finished installation... lower end of wood adaptor mounted on the 1/2" boss of the treadle platform... upper end of threaded rod threaded into the ball bearing race piece on the drive wheel crank.. just as if the factory had planned it that way.




Many thanks to Bernie for the explanation and pictures. I'll be making one of these myself as soon as I get ahold of some ball bearing I need for the crank race on the frame I'm assembling...

Captain Dick