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:
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:
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.