DIY Marble Rolling Pin Grain Mill

As is the case for many of you here on the forum, the switch to all-grain inevitably pushed me to the need for a grain mill. I was on a tight budget and as such could not justify the expense of a Barley Crusher or Monster Mill. One day I stumbled upon the remains of our broken marble rolling pin (the handle snapped) and a light bulb went off. So I decided to convert this marble pin into a grain mill. Unfortunately, I wasn’t smart enough to document the build as I went along so all I can do is describe it and share some pictures of the finished product. However, the construction is relatively straight forward for the DIY types out there so you should be able to figure it out from the pictures.

First off, here are the pictures of the mill:
http://diymarblerollingpinmill.shutterfly.com/35
http://diymarblerollingpinmill.shutterfly.com/31
http://diymarblerollingpinmill.shutterfly.com/32
http://diymarblerollingpinmill.shutterfly.com/33
http://diymarblerollingpinmill.shutterfly.com/30
http://diymarblerollingpinmill.shutterfly.com/34

The basic design consists of the marble rolling pin (approx. 2” in diameter originally) mounted on a steel 1/2” shaft. Because marble rolling pins are very smooth, and because the diameter is relatively small, it must be grooved. For this, I used a 4-1/2” angle grinder equipped with a diamond masonry disc (Tool detail). To cut the grooves straight and parallel, I clamped the rolling pin down to my workbench using the wood cradle that came with it. I then made a jig that allowed me to slide the grinder along the rolling pin at a fixed depth. I set the depth of the groove to approx. 1/16” and spaced them approx. 1/8” apart. Once the pin was grooved, I pushed the 1/2" steel shaft thru the pin (after enlarging the hole using some sandpaper) and secured it in there using some 5 minute epoxy.

For the overall frame of the mill, I used some scrap 5/8” plywood I had left over from another project. One of the angled hopper boards is mounted on pivot pins to allow for gap adjustment. I can adjust the gap from 0 to >1/4” and anywhere in between. This moving plate extends below the roller and directs the crushed grain into whatever container you choose to use. This adjustable plate is also equipped with a removable crush plate. I used aluminum because it was available, although ideally stainless steel would likely be better. The wood was all coated with three coats of polyurethane finish to seal it all up.

The bearings for the roller are simple aluminum fan bearings available at most hardware stores. I lubricate the bearing with a couple of drops of canola oil before I mill. In hindsight, next time I would go with a bronze bearing instead. I can drive the roller either using a hand crank (that I also made, but didn’t show here) or using a drill with a 1/2" chuck (my usual method).

Once the whole mill was assembled, I put a full sheet of coarse (80 grit or coarser) sandpaper over the adjustable plate and closed the plate right against the roller. I then connected my drill and ran it at high speed to sand down the roller so that it is parallel to the adjustable plate and is balanced over/on the axle. This also made the grooves shallower which allows for a better crush.

You’ll notice some red tape and poly affixed to the hopper. This is to cover the gaps on the sides (the rolling pin is not uniform and therefore it is impossible to get a perfect fit) and along the fixed hopper plate (after sanding down the roller, this gap got larger and allowed uncrushed grain to fall thru). Not the prettiest fix for the gaps but its cheap and it works.

Finally, how does it work? Well, awesome in fact. My efficiency into the kettle is consistently around 80% (approx. 86% conversion efficiency) so I am happy with that. For a 4.5kg (10 lb) batch it takes me about 8 minutes to double crush the grain (6 minutes for the first pass, 2 minutes for the second). I double crush because I am paranoid and because it only takes an extra 2 minutes so why not. I ended up setting the gap to essentially 0” (relative to the high point of the groove) since the barley kernels tend to settle into the groove and get pulled in to be crushed. So basically the gap is the depth of the grooves. So for barley malt this setup works great and I have attached pictures of the crush below:
http://diymarblerollingpinmill.shutterfly.com/28
http://diymarblerollingpinmill.shutterfly.com/29

Unfortunately, it does NOT work for wheat. The wheat kernels are too small and just pass thru the mill unaffected. As for a parts list and cost, I don’t have one. But, the rolling pin and plywood were essentially free. The bearings cost about $2.50 each, and the miscellaneous screws etc. are probably another $2-$3. If you were buying everything, I think you could easily keep this under $20 if you watch garage/rummage sales for the rolling pin.

Well, I got a little more long winded than I had intended so I will end it here. All in all, I am very happy with how this project turned out and I would recommend it to anyone who likes to build things or who has more time than money. If anyone has any specific questions about how this is built fire away and I’ll do my best to answer them.

Cheers,

Greg

I like,
nice job!!

Put the wheat in the blender?

Seriously, very nice craftsmenship.

I'm very impressed with both the design and your workmanship. The crush looks to be very good with most of the husks more or less intact. There must be a way to texture the rolling pin so that the grooves are not as deep. I was going to suggest tightening the gap just a tiny bit more, but you said you already have it maxed out. What happens if you run the grain through it a third time? I also like the single roller design. Seems it would be less prone to shredding the husks than multiple roller mills.

Maybe it would be possible to make the mill adjustable by the piece of wood instead of the roller. Have you thought about adding a second roller?

Catt22: The depth of the grooves was difficult to limit given the way I did them with a grinder. If I wanted to make them shallower, I think the best way would be to sand down the roller more and minimize the depth. As for running it thru a third time, I haven't tried it yet since I was getting good efficiency and didn't see a need.

Salzar: I think you misunderstood the design. The gap IS adjusted by the pivoting hopper plate. As you pivot the plate the gap is either closed or opened. As for a second roller, that is certainly possible. But it makes building it more difficult and I don't know that it would necessarily be any better.

Cheers,

Greg

It appears the roller crushes against the hopper plate. If this is so, I would install a piece of sheet metal over the plate. This will increase the life of the plate and keep wood and glue particles from the plywood out of your beer.

Edit: never mind I reread your post and found the crush plate.

Very ingenious! I wonder if you could also just take a marble rolling pin and affix some very course heavy duty sand paper to pull the grain through the gap instead of trying to groove it. You may have to replace it every so often, but it might last quite a while, depending on how tough the paper is.

Ah yes, adjustable hopper plate is what I was thinking.

The second roller would have a better surface to crush against. I dunno the reason for 2rollers over 1, but my speculation is that having the non driving surface move with the kernal provides only crushing, instead of crushing and smearing.

I've made this crusher almost exactly. lil sparky, the sandpaper won't last through a batch before it gets torn to shreds. Ask me how I know! Grain is very hard on a grinder. I did the crush adjustment on the crush plate side by putting pegs into the sides near the top and making a pivot point about 1/3rd of the way up the bucket. I used a wooden rolling pin, but a marble one would be better, imo. Or if you're full of cash, buy a SS rolling pin and knurl it somehow