Design of mill (metallurgy)

[rpe290]

Would it matter if a mill was made of carbon steel vs stainless steel for homebrewing? Or even Al for that matter? And does anyone know how big you must go to not use knurling (I saw 4 in OD in another post).

(no calls about being cheaper to buy one, that's not the intent )

 

[Old_mil_guy]

Hardened carbon steel should last longer than stainless. Stainless should last longer than Aluminum. I'd be guessing on roller diameter but I think driving both rollers would be better than a 4" diameter.

 

[Toymaker]

You need knurling on the smaller rollers to pull the grain through. If you don't have knurling you have to go with bigger rollers so the grain won't slide. I have also seen reference to 4" diameter rollers. I have not built one "yet" so I can't say for sure if un-knurled 4" diameter will work or not.

 

[audger]

are you talking about the actual rollers, or just the mill overall...? i would not use aluminum for the rollers. id imagine they would get beat up pretty quickly

 

[Bobby_M]

There's probably some leeway on roller diameter but that would depend on the surface finish. Even if you don't do a true knurl, you would have to go pretty big if the surface was nearly polished vs. mill finish vs. something rougher. I can imagine putting some 40 grit in a belt sander and running it parallel to the drive shaft would create some good grip.

 

[rpe290]

You need knurling on the smaller rollers to pull the grain through. If you don't have knurling you have to go with bigger rollers so the grain won't slide. I have also seen reference to 4" diameter rollers. I have not built one "yet" so I can't say for sure if un-knurled 4" diameter will work or not.

I can get 2 1 foot long pieces of 6" diameter SS tube (thick walled) for $23...I can do the rest...maybe only need 6-8" long?

 

[benz72]

How are you doing precision centering for the axle? Even a little bit off seems like it could vary the gap by an unacceptable amount. This could be compounded by two slightly off center mountings.

 

[phoenixs4r]

How are you doing precision centering for the axle? Even a little bit off seems like it could vary the gap by an unacceptable amount. This could be compounded by two slightly off center mountings.

This. Also remember the longer the mill rollers the more grain you will be crushing at a time, the stronger the motor will need to be.

 

[rpe290]

I do appreciate the sentiment, but I will not have any problems designing to tolerances and fabricating things--its one of the few things in life I do well

 

[Old_mil_guy]

So what kind of wheel / axle would you run inside the ss tube?

 

[rpe290]

So what kind of wheel / axle would you run inside the ss tube?

Either press-fit or weld a cap on the ends with a bearing boss on it. After welding/pressing, put it between centers and turn everything concentric. (in other words, make 1 "united" piece out of 3 pieces)

 

[kevink]

How are you doing precision centering for the axle? Even a little bit off seems like it could vary the gap by an unacceptable amount. This could be compounded by two slightly off center mountings.

You're only crushing grain. Even a severely worn out lathe is capable of doing this work. Let's say you're lathe is really, really, worn out and turns bad tapers when you want to turn a cylinder. Just make your two rollers and reverse one so the headstock end of one roller is on the same side as the tailstock end of the other roller when the mill is assembled. You should have equal spacing between the rollers when the centerlines are parallel.

 

[rpe290]

You're only crushing grain. Even a severely worn out lathe is capable of doing this work. Let's say you're lathe is really, really, worn out and turns bad tapers when you want to turn a cylinder. Just make your two rollers and reverse one so the headstock end of one roller is on the same side as the tailstock end of the other roller when the mill is assembled. You should have equal spacing between the rollers when the centerlines are parallel.

Haha, good idea there for using what you have (in a time saving fashion)!

My motto is "The definition of a good machinist is that they can make good parts on bad machines!"