Grain and Rice Dehuller Attachment for the Corona Grain Mill

Corona Grain Mill Dehuller Instructions
We searched for eight years to find an affordable grain dehuller. Nearly all the dehullers we investigated cost anywhere from three hundred fifty dollars to several thousand dollars. In 1993 we found a solution to the affordability problem. Thanks to Allen Dong and Roger Edberg, a dehulling attachment was invented which could be adapted to the Corona Grain Mill. The device was patented under a public domain patent and dedicated to the peoples of the third world. For several years we offered instructions for fabricating this simple attachment, however we found that the materials or the means of fabrication were not accessible to our customers. As a result we contacted a manufacturer who could fabricate and supply the dehuller. Unfortunately, this manufacturer is no longer in operation. We're told that sometimes dehullers show up on eBay. You can find instructions for making it yourself here.

Unfortunately, Corona Grain Mills themselves are now hard to find as well; as of 2011, Corona Grain Mills are being made in China, but there is no U.S. Importer for them, so eBay is probably the best place to look for used Corona Grain Mills.

The dehuller attachment is a metal disk to which a gum rubber disk has been attached with cyanoacrylate glue. It is designed to replace the stationary disk of the Corona Grain Mill. Since the replacement is not permanent, the mill can be converted back to its original purpose.

To install the dehuller:

--Remove the augur and rotating disk from the Corona Grain Mill.

--Remove the stationary disk from the mill, by unscrewing the three screws.

--Mount the dehuller on the mill with the rubber side facing out. Insert and tighten screws.

--Reinstall the augur and rotating disk.

Types of seed dehulled, and how to adjust the dehuller spacing:

After installing the dehuller, adjust the spacing between the stationary rubber disk and abrasive disk. At first it may take some experimentation to determine the proper distance between the plates. The objective is to achieve a spacing that will crack the hulls from the grain without cracking the grain itself. Initially, the plates should be spaced so that at least 85% of the hulls are removed on the first pass through the mill. With practice,rice can be dehulled in one pass through the mill at 95% to 98% efficiency. Other grains are dehulled at 60 to 70% effectiveness on the first pass and therefore require several passes through the dehuller, especially if they are soft grains. The dehuller can be used effectively on wheat, millet and buckwheat, but not oats. We recommend growing hulless oats which have a soft hull and can be ground directly into flour or cracked in the grain mill without dehulling. The effectiveness of sunflower seed dehulling varies according the variety of sunflower. Variety selection is critical for success. Large, flat-seeded types such as 'Mammoth' do not work well in the dehuller. We recommend medium-sized, black-seeded types which have a conical seed shape. Black-seeded varieties are best because it is easier to distinguish the hulls from the seed. 'Hopi Dye' sunflower has hulls that split more easily than other types. Even so, some hand-picking of seed will be required to remove chaff not removed by winnowing.

Separating the grain from the chaff: the grain can be separated from the chaff in several ways, depending on the method most convenient for you:

--Place the grain/chaff mixture in a large bowl or tray and then slowly pour the mixture into another bowl or deep tray in front of a fan placed several feet away. The fan will blow away the chaff as the mixture falls though the air. For cleaning small amounts of grain, try placing the hulled grain in a mixing bowl and then blow out the chaff with a hair dryer.

--Winnow the grain by tossing the mixture up and down in a large bowl while there is a gentle breeze or wind. The chaff will be carried away by the wind.

--Pass the grain/chaff mixture through sized screens. The best screens for this purpose have oblong holes, but the screens are difficult to find or expensive to buy. Sometimes the rough chaff can be removed by screening followed by winnowing to remove small chaff.
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