For some time I have been experimenting with various ideas to crush malt. The first time I used grains was in a partial mash porter and tried to crush the malt with a beer bottle and a rolling pin - not very successful. I then came across a diagram in a book called Wood Working for Home Brewers and Wine Makers, which used 2 rolling pins in a wooden frame - it sort of worked but left me with acing hands and wrists. This was followed by a mill with STEEL rollers. The roller were made by knurling 25 mm diameter round bar and machining a 16 mm shaft on each end. They were 100 mm long and mounted in a box made from 16 mm ply wood. The gap was adjusted by 2 screws pushing a slider . The gap was often uneven. This worked OK, but the nip angle was to large and both rollers had to be cranked and both had to be knurled. To have steel Knurled is expensive, and the next design had to eliminate some of the knurling. To achieve this I increased the diameter to 50mm which worked.
I was still not happy with the gap adjustment and devised a cam system which has been incorporated in the latest design. The drawings on the following page shows the dimensions that I used for the rollers and cam shaft. I used mild steel although industrial mills use hardened steel rollers to improve wear resistance - for home use the extra cost is not warranted. The shafts run in oak bearings made from 2 off 110 X 100 X 20 oak blocks and held together by 4mm ply wood side plates. The mounting block is a 110 X 60 X 50 pine block which is clamped to a table with a G-Clamp. The crank handle is made from a piece of 25 X 5 flat bar with an 8,5mm holes drilled in end and the other taped M8. One end is screwed tightly into the driving roller with an M8 bolt and spring washer, the other end has the handle attached to it. The handle can be made by cutting 100mm off a broom stick and drilling a 9mm hole down the centre. A 110 mm length of threaded bar will work as a shaft screwed into the taped hole on the crank and locked with a lock nut. The cam adjusting lever is similar to the crank handle but has a length of only 20 mm between centres. Use an M8 bolt to lock the adjusting lever to the idler shaft. Note the location of the cam lobes. I suggest that the lever be lined up with the lobes indicating the opposite side to the where the gap is. The adjusting bolt can be made by filling the "point" of an M8 bolt down to a diameter OD about 4,5mm. This then screws through the taped hole in the adjusting lever and into one of the 5 adjusting holes on the bearing plate on the clamping side of the mill box.
