I just picked up an old grindstone that was for sale on Facebook marketplace. It is about 11 1/2" in diameter by 2 1/2" wide and the stone seems to be in good condition. The crank shaft for the stone is missing the arm for the treadle which appears to have snapped off at some point, and someone put a pulley on to drive it at some time. I know that these stones should not be spun at high speeds and plan on making it treadle driven once again. What I need to know is what the offset for the arm needs to be. I will also have to make a new frame for it.

~Duncan

Have you done a web search? I did a quick one to see if I could find drawings and dimensions without luck. I did find a couple pages of images I'm sure you can use to determine the crank length. 

I'd disregard the chain saw powered one though. 

Frosty The Lucky.

https://images.search.yahoo.com/search/images?p=how+a+treadle+grindstone+works+pictures&fr=crmas&imgurl=https%3A%2F%2Fs3.amazonaws.com%2Ffinewoodworking.s3.tauntoncloud.com%2Fapp%2Fuploads%2F2019%2F04%2F27172855%2Fnew_grinder_small.jpg#id=27&iurl=https%3A%2F%2Fs3.amazonaws.com%2Ffinewoodworking.s3.tauntoncloud.com%2Fapp%2Fuploads%2F2019%2F04%2F27172855%2Fnew_grinder_small.jpg&action=click

Hey frosty, I did do a web search but didn't find anything so I thought that I would try here. I am hoping that some members may have a grind that they could measure the offset on. If not, i'll just estimate. I don't think it needs to be super specific.

Good Morning Duncan,

They are not meant to turn fast, they are meant to Finish or sharpen an Axe or something similar. The were put together with locally available material, not to a BluePrint. The lever will be long enough to work with your foot pedal, comfortably. You may have to weld a stub onto the axle, or make another axle to fit modern available bearings/bushings. To grind off a lot of material, use a powered grinder and finish on the Wet Stone (water).

Neil

I have not worked on treadle grind stones but I have restored several spinning wheels which use a similar motion, either single or double treadle.  The off set of the crank to the axle is usually about 2-3".  Then, the connectors from the crank to the treadle (on spinning wheels are called "footmen") are made with a key hole shaped opening to go over the knob or flange at the end of the crank.  The length of the footman is determined by the distance from the end of the crank at the bottom of the stroke to the horizontal position of the treadle.  Traditionally, the treadle and the footman is connected with a leather thong.

My lat wife always preferred to spin on a wheel barefoot because she said it gave her a better feel and control.  I understand that is traditional for spinners.  You probably don't need that sensitivity for a grand stone.

11 1/2" seems a bit small for a treadle grindstone to me since the surface speed would be slower than a larger diameter stone.  You might want to rig up some sort of multiple pulley system to increase the rpm.  That has been done on spinning wheels.  Look up a "miner or minor's head."  There were several patents for such things in the early 19th century.

Please let us know how the project goes and give us pictures of the final set up.

"By hammer and hand all arts do stand."

If your wheel has been converted to electric, the size of the motor & wheel pulley determine the RPM of the wheel. I have one converted and the wheel turns very slow (can't remember the RPM right off. It has a drip watering system and works a treat for final finishing sharp stuff. The only picture I have of mine is this one, it's in the right background.

Yesterday I fixed the crank shaft for the stone (I decided to do about a 2.5" offset)  and today I built the frame.  All I need to do now is make a treadle peddle.

I've taken a few pictures of my progress.

I've attached the treadle and my stone is now operational.