I've just completed a single roller malt mill. It crushes the malt against an adjustable tangential steel plate. I puzzled for a long time over what to use for the roller since I wanted to avoid spending alot of $$$ at a machine shop on a metal one. I decided to use concrete. Got a 4" diameter PVC pipe cap, drilled a 5/8" hole in it's center, inserted a 5/8" steel rod which had a 5/16" rod inserted into a hole (serves as torque reinforcement and enhances the bond of the concrete to the shaft). The thing looks like this:
+========= <----------4" pipe cap form | ++ | ||<---------------5/16" rod | || +-------||-----------+<---5/8" rod shaft +-------||-----------+ | || | || | ++ +=========I used fast setting "quickcrete" to fill the pipe cap. It's available in 10 pound yellow plastic buckets and has no gravel in it. After the concrete set (24 hours), I removed the pipe cap by cutting slots along it's periphery with a table saw and then pried off the plastic in chunks. The roller was then mounted into a wood frame with ball bearings. It was a tad out of round and had a slight taper along it's axis so I used a right angle grinder with a masonary disk to true it up. Did it by rotating the roller while applying the grinder.
The mill works great and cost less than $20. I'd worried it might produce too much flour, however, in a pound of grain, there's only about a tablespoon or so of flour. I'm doing my first partial mash today. Wish me luck...
I recalled an old post to HBD which stated that large rollers don't require texturing so I casted a 7" dia. x 1.5" wide one using a plastic bucket for as a mold. It was made in the same manner as the 4" orginal roller. It also glazed over so I added texturing with a cold chisel- 1/16" deep grooves every 1/2" or so. The concrete takes a groove better if done within a day or so of casting. The grooves were made with the chisel held parallel to the roller's axis.
The ale made with the grain was fine. It takes (a guess) 7-10 ft-lbs to turn it due to the large wheel diameter and is not too fast since the grain feed width is just a tad over 1" wide (about 2.5 minutes/lb.) The crush is good- not too much flour however, the grain husks are somewhat torn. A post to the HBD advises that wetting the grain before crusing might help. Methinks the tearing is due to the roller grooves and the grains being dragged across the steel plate.
The next experiment will be to a motorized two roller (4" diameter) mill. Hopefully texturing won't be needed.
If anyone else is cobbling together their own mills and doesn't post to the HB Digest, I'd really like to hear about their mills!