Motorizing Wondermill hand grinder

[jimmycthemd]

I've been bored lately so I decided to motorize my Wondermill hand grinder. Here are a few pics:







The motor/pulley is off a broken drill press. The oak for the platform and bearing mounts are from my reject/scrap pile. The intermediate pulley shaft is 1/2 inch drill stock cut to length. The intermediate pulleys are from Tractor Supply Co. and the pocket bearings for the shaft are from Graingers. Total out of pocket cost is about $60 not including the grinder of course.

The motor spins at 1750 rpm. The step-down to the first pulley is 4 to 1 and from the shaft to the grinder is 10 to 1, giving me a total step-down of 40 to 1 or 43.75 rpm. Wondermill recommends a max grinding speed of 80rpm so I'm well within the limits.

[Rmplstlskn]

Try to fabricate some belt guards... That is a lot of open pulleys in an area where your hands, arms and clothing will be near...
Other than that, looks great! Well done...

Rmpl

[jimmycthemd]

Try to fabricate some belt guards... That is a lot of open pulleys in an area where your hands, arms and clothing will be near...
Other than that, looks great! Well done...

Rmpl

Yep, the belt guards are on my list. I picked up the parts last week and glued/sanded/stained the wood last weekend. Put it together in my free time while working from home this week during the ice storm. I have to pick up some sheet metal for the guards.

Thanks for the complement :D

[610Alpha]

It looks really nice...knowing how to calculate the pulley's is something I don't know...but I am sure google could help me.

[jimmycthemd]

It looks really nice...knowing how to calculate the pulley's is something I don't know...but I am sure google could help me.

It's easy. The first pulley is 1.5 inches, the second is 6 inches...6 / 1.5 = 4. I verified when I got them hooked up. Second pulley i1 1.5 and the one on the grinder is 15. 15 / 1.5 = 10. Again, verified when it was hooked up.

[rockriver]

I'm impressed jimmy c!
great post.

[motesjm]

Great job Jimmy!

[jimmycthemd]

After using the mill for a while, I've learned two things:

1) The set screw (actually a bolt) on the mill pully is undersized. It's a 1/4 18NC. It stripped out in the middle of a grind, ruining the threads. Cheap fix for that. I went to my local hardware store and got 3 5/16 18NC bolts. The shaft has three tapered flat areas that the handle fits onto (120 degrees offset). I drilled out the existing set screw hole and tapped it for the 5/16th bolt. I repeated this for the other two at 120 degrees offsest to match the shaft. This should hold up a lot better.

2) I went back to the store where I bought it (same one I get my grain from) and looked at the Country Living mill. My Wondermill cost about $230 and the Country Living is about $400. There's a reason the Country Living mill is more expensive. It not only has a set screw, it is keyed so there's virtually no chance of the failure that happened on mine. One of the cases where you get what you pay for :-)