Wednesday, January 8, 2020

Grain Mill Part 1 - Housing

We begin the grain mill build with the outer housing.  I decided to make this from some scrap pieces of 1/2" thick stainless steel.  Firstly, squaring up all the sides in the milling machine.
Next, I drilled screw and dowel holes in the side pieces.  The screw holes were drilled 9/32" to clear 1/4"-20 screws, and the dowels were reamed for 1/4" dowels.  The dowels ensure more precise alignment of the housing pieces.
Then, the corresponding screw and dowel holes were drilled into the end pieces.  Here the screw holes were drilled and tapped 1/4"-20, while the dowel holes were drilled for a slip fit.
Here is how the 4 housing pieces fit together.
Then bolted together.
The next step was to create the bores and slots for the bearings.  Here the dimensions have been worked out.
First, rough drilling the bore and slot locations.
Next, plunge cutting most of the material for the slot.
Then, finishing the slot clearance.
After that, the slot step was milled.  This is where the movable roller's bearing will ride in.
Then for the fixed roller, machining the bores for its bearings.
Here is how both bearings will fit.
I noticed a lot of chatter when machining the first bore, so I switched to a larger boring head and carbide boring bar for the second one.
The resulting finish was significantly better compared to the original high speed steel boring bar.
Mounting holes were then drilled in the top and bottom of each piece.  These will be used to attach the hopper on top, and to secure the grain mill to a base.  #10-32 holes were used for the hopper, and 1/4-20" for the base.
Lastly, drilling and tapping 1/4"-20 holes for the spacing adjustment screws.

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