Motorized Grain Mill

Here’s how I motorized my standard-edition JSP maltmill. The mill works just fine hand-cranked or driven with a drill but this was a fun project!

I started out by getting the electric motor settling for an a used 1/2 horse motor I found on eBay. It was $22 shipped, not a bad price. It turns at the typical 1725RPM and has a 5/8″ shaft.

Mill Sheave

Mill Sheave, Hub, and BushingTo scale down the motor speed I used an 11″ sheave on the mill and a 1.5″ sheave on the motor. In theory this turns the mill shaft at 235RPM. Farm & Fleet proved to be a good source for the hard-to-find large sheaves; Grainger sells them but they’re very expensive. F&F’s sheaves & hubs are sold separately so one has to spot-weld them together, but this is why the world has brothers-in-law, right? Furthermore the smallest hub bore available was 1/2″ so I had to get a 3/8″ > 1/2″ bushing for the mill shaft. In this photo you can see the separate hub as well as the bushing. F&F didn’t have a shaft bushing with the keyway notched out but they did have a solid brass reducing bushing out of which I was able to grind a slot. Not pictured is the square key inserted into the keyway. Crescent-shaped woodruff keys were too tall to fit in between the shaft and hub. The belt is a 50″ ‘A’ belt. It rides perhaps too deep within the mill sheave but the ‘B’ belts were too wide to fit in the motor sheave.

Plywood base

There’s not much to say about the motor and mill mounting, they’re both simply bolted to the top of the plywood. A water cooler jug works wonderfully as a grain hopper, they’re just a bit finicky to securely mount. I went with kind of a ring support for the water cooler; it’s wide enough to support the jug by its shoulder. The threaded rod lets me adjust the height of the hopper to get the snout right down by the rollers.

Circular hopper mount

On the first test run malt was sprayed everywhere so I made a cover for the mill assembly. This is just a piece of plexiglass with a hole Dremel’d in for the hopper snout. It does a great job of keeping malt from spraying everywhere in addition to acting as a finger guard! With the hopper poked into the plexiglass I haven’t found the need for side supports for the hopper.

A sample of the crush:

Some Briess 2-Row ran through the mill

A lame video:


I’m pretty happy with the results. From the video one might surmise that malt is going in between the roller and sidewall but in fact it is not because the gap there is smaller than a kernel of barley. I think I’d like the speed to be slower but the crush looks like like when I hand-cranked it or used my drill.

In an earlier version I mounted the motor on a hinged board which allowed the motor’s weight to tension the belt.  In practice this didn’t work very well because the mount would bounce while in operation causing the belt to occasionally slip.  I could have solved the bouncing issue using a spring to hold the board down but this was too much fuss so I just bolted the sucker down.

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