Introduction: Table Mounted Oat Crusher

About: With a Master in robot engineering i'm very interested in open source technology and the developpment of simple and local energy sources. Besides that I'm a nature lover, wilderness guide and vision quest tuto…

Freshly crushed oats not only taste a lot better, they are also more healthy because there's no time for nutritients to oxydize. And it's also fun to do, especially children love it.

This machine is very similar to the other oath crusher in my instructables. Instead of wall mounting, this one can be fixed on a table by two clamps.

This oat crusher can be made of only recycled materials. If you speak german, I recommend the leaflet "Einfälle statt Abfälle - Die Müsliquetsche" distributed by "Packpapier Verlag", which contains very detailed instructions.

The pdf file here contains all the compacted instruction for the fabrication and assembly of the machine. If it helps you, you can also get the 3D CAD files (SolidWorks) of the machine as shown in the picture. Just contact me.

To fabricate the different parts, rely on the pdf file in the next step, showing all the measures.

Step 1: Material

The material is mostly Recycling (see drawings in the pdf file for exact measures. Attention, if the cylinder diameter differs from 48mm you have to adapt the measures! The words in brackets are the german names of the parts used in the drawings and CAD-files)

  • Wooden block (better hardwood) for the base (basis), ca. 40x90x140mm
  • Hardwood bars: 4 struts of 230mm (Strebe), ca. 12x20x930mm
  • 2 Hardwood blocks, min. 60mm long, min. 50mm Ø, very dry, for turning the cylinder cores (Walzen)
  • Thick metal pipe for the cylinders (Walze), min. 50mm Ø, min. 110mm long, e.g. Water pipe
  • Metal rod for the axles (Achse) and the crank (Kurbel) 10mm Ø, min. 50cm long
  • Thin Metal sheet, ca. 0.3mm, e.g. from olive oil tin, for the slide (Rutsche) and the funnel (Trichter)
  • Square-necked Mushroom head bolts (coach bolts): 2x M6 x100mm, plus washers and two wingnuts
  • Some 2mm-Nails for securing the cylinders on the axles and some 30mm wood-screws, 4 small 15mm wood screws to fix the funnel and four 15mm Nails to fix the slide.
  • Two small cheap clamps (ca. 50mm opening) to fix the machine to the table

Step 2: Fabrication of the Parts

If you fabricate the slots for the struts in the base very precise, the whole thing gets quite sturdy and might even omit the screws. Or screws only to keep the struts removable.

The deep holes for the clamps should be adapted the the clamps used.


Out of a thick-walled metal tube with at least 50mm Ø you fabricate the cylinders. The smaller the Ø, the deeper you have to make the knurl to be sure the corns don't stall. The knurl is made diagonally, either with a small metal saw or with a chisel, in which case you need to file it over afterwards to take away the burr.

The core is turned out of extra-dry hardwood, either on a turning machine or improvised with a drill. Once cylinder, core and axle are assembled properly, all is secured by two 2mm-Nails put in a hole drilled through all three of them and then sawed off.

Alternatively, the core can be replaced by two welded metal plates or a concrete core. As long as it is tough and properly centred, do as you wish ;-)

The crank handle can be self-made or you buy a simple file handle and drill the hole open to 10mm. Secure the handle on the crank with a small nail going through the notch at the end of the crank.

Sheet metal parts

In the sketch you can see how the two sheet metal parts should be cut. For the exact measures of the slide check the drawings, the funnel size can vary. With small pliers you can curl and crimp the lower edge of the slide and the upper edge of the funnel. The seam on the funnel is also crimped as you see in the sketch. The seam should be soldered or riveted additionally.

The wiping flaps on the slide should have neat straight edges, which are going to lie on the cylinders.

Step 3: Assembly

  1. Main structure: Arrange the four struts correctly and fit them into the slots on the base and glue and/or fix them with screws. (Image 1)
  2. Now you can mount the two cylinders (put some vaseline on the axles to lessen the friction). First fit one cylinder into the bearing, then, with some force, add the other one. Now put the two coach bolts into the holes in the struts, add the washers and wingnuts. (Image 2). If the struts are very stiff, you can add some spring travel by adding one or two spring washers under each wingnut. More spring travel allows for more error on the cylinder centring and allows you to grind larger grains. With the wingnuts you can easily adapt the squeezing force.
  3. Now place the slide (check little pre-drilled holes for the nails on the struts) and check, if the wiping flaps properly lie on the cylinders (image 3). If not, adjust. With adjustable pliers force the four 15mm nails into the holes to fix the slide (or just use small screws).
  4. Mounting the funnel (Trichter): Put the funnel onto the four carrying bars and either adapt the lower opening or file away on the slopes on the carrying bars (or add a washer if necessary) until the distance to the cylinders is 1mm at the most and the funnel doesn't touch the cylinders. Then punch four holes in the right places into the funnel with a pricker and pre-drill holes into the carrying bars (image 4). Fix the funnel with four small (10-15mm) countersunk screws.
  5. Ready to use... :-)