How to Build a Workhorse Grain Mill
Salutations. I'll assume that if you are reading this they haven't tracked you down and hauled you off to the loony bin yet for being a dedicated member of my cult following. But then, you still have that to look forward to. Hopefully, they'll let you finish this project and use the mill once or twice before they put you away. To that end, let us commence. This time we'll make the grain hopper, the catch bin for the milled grist, and some additional pieces of grain / dust shielding.
Materials & Cutting List - Remember that the actual thickness of 2” construction lumber is
OK you slackers, let's get to work. First the grain / dust shielding. Test-fit the 7-1/4” X 7-1/4” piece of sheet metal into the top of the mill - it should be placed on top of the bearing dust shields previously installed, and should fit loosely in the area between the bearing retainers and between the front and back inside surfaces of the frame. Put reference marks on the top surface of the sheet metal to identify the position of each side - front, back, left, right. If the piece does not slip easily into place, determine whether it is too big from front to back and/or side to side. If the fit is tight from side to side, trim 1/16” from one side of the sheet metal. If the fit is tight from front to back, trim 1/16” from either the front or the back edge of the sheet metal. Repeat as needed until the piece slips easily into place. Now place the sheet metal on a flat work surface and lay it out as follows. Find the center point by drawing lines across the piece from corner to opposing corner, the lines will cross at the center point. Draw a line through the center point and parallel to the front edge of the piece. Measure and mark points A & B on the line 1-7/8” to each side of the center point. Through each of these points, draw lines parallel to the left and right sides of the piece. Measure and mark points on these lines 1-1/16” to each side of points A & B. The resulting array of points should look like the capital letter “I”. Next, use a hammer and cold chisel to cut through the "I” on the sheet metal. This is best done on a steel surface, if available, but can be done on concrete. Once the “I” has been cut, carefully bend the resulting flaps downward equally until a 1/2” to 5/8” gap is opened along the A-B edges of the flaps. Re-orient the shield and slip it back into place on top of the bearing dust shields - the flaps should be close to but not quite touching the surfaces of the rollers, bend them as needed to achieve this fit.
Now get the 3-1/2” X 4” pieces of sheet metal and lay each of them out as follows. Find the center point of each 3-1/2” side, mark the points A & B, then draw a line through the center points parallel to the 4” sides. Measure and mark the center point of one 4” side and mark this as point C. Now get that left over piece of roller pipe that I told you not to throw out after you made the rollers, and set it on one of the work pieces so that the circumference of the pipe intersects point A and point C. Draw along the circumference of the pipe to form an arc between points A and C. Repeat this procedure with the pipe oriented on points B and C. Repeat the entire procedure on the second work piece. Now use tin snips to carefully cut along the arc lines on each work piece. Next, place one work piece into the jaws of a vise so that point C is pointing up and the top edges of the vise jaws are exactly on and parallel to the A-B line. Bend the entire area protruding from the vise jaws 90 degrees so that the work piece forms an “L” shape. Repeat this procedure with the second work piece. Finally, drop each “L” piece onto the top of the 7-1/4” square shield so that the bend line of each “L” is snug against one of the bases of the “I” and point “C” is inserted into the gap between the flaps. The arcs that converge at point “C” should be close to but not quite touching the surfaces of the rollers, trim as needed to achieve this fit.
Make the grain hopper next. Take the 1-1/2” X 7-3/16” X 15” pieces of construction lumber and lay them out as follows: Draw lines along the 15” length of the 7-3/16” wide surface, parallel to and 3/4” in from each side. Make hash marks on each line at 3/4” in from each end and at the center point (7-1/2” in from either end). Set drill points at each hash mark and drill a 7/32” diameter hole at each hash mark - make sure the holes are drilled perpendicular to the face of the work piece. Use a 3/8” diameter drill bit to counter-bevel each hole just enough to fully seat a #10 X 2-1/2” wood screw with the head of the screw flush to the face of the work piece. Set these pieces aside for now.
Next get the 1-1/2” X 4-1/4” X 15” pieces of construction lumber and the 4-5/8” X 4-1/8” pieces of lauan plywood. With the construction lumber pieces laying flat on a work surface, measure and mark the center point of the 4-1/4” width at the edge of one end of each piece. Measure and mark points 3/16” on either side of the center point. Take one piece of plywood and stand one of its 4-5/8” on edge on the surface of one of the pieces of construction lumber so that one end of the side of the plywood facing the center of the construction lumber intersects with the edge of the construction lumber at one of the edge points offset 3/16” from the center. The opposite end of the edge of the plywood should then be positioned so that the side facing the center of the construction lumber intersects with the edge of the 15” length of the construction lumber. Holding the plywood firmly in this position, draw a line on the construction lumber along the edge of the plywood facing the center of the construction lumber. Repeat this entire procedure on the opposite side of the center point on the construction lumber. When you have finished, the lines drawn will form a blunt pointed VEE on the surface of the construction lumber - the gap at the point of the VEE should be 3/8” wide. Now set up your radial or table saw for angle cutting, mount a fine plywood blade, and cut a slot exactly 1/4” deep precisely along each leg of the VEE, removing material on the side of the line AWAY from the center of the construction lumber. It may be necessary to make more than one cut to make the slot wide enough to accept the edge of the plywood with a snug fit. Do not make the slot more than 1/32” wider than the edge of the plywood, nor less than 1/4” deep - practice on some scrap wood to hone your skills.
When the slots have been cut into each of the construction lumber pieces, take one of the pieces and press the plywood pieces into the slots so that the ends of the sides facing the center of the construction lumber are flush with the edges of the construction lumber. Tap the plywood pieces down to make sure they are snug to the bottom of the slots. Now align the free edges of the plywood pieces with the slots in the second piece of construction lumber and press the pieces together, again tapping to make sure the plywood is snug to the bottom of the slots. At this juncture, a small amount of material on the sides of the plywood facing AWAY from the center of the construction lumber will be protruding beyond the edge of the construction lumber. This material should be carefully removed with a power sander so that the exposed edges of the plywood are flush with the sides and ends of the construction lumber pieces. When this has been done, disassemble the plywood pieces from the construction lumber, run a thin bead of wood glue along each slot, and then reassemble making sure the plywood pieces are flush with the edges of the construction lumber pieces and snug to the bottom of the slots. Allow the glue to dry thoroughly.
When the glue is dry, set the assembly lengthwise on the work surface with the 1-1/2” edges of the construction lumber on one side facing UP. Get the 1-1/2” X 7-3/16” X 15” pieces of construction lumber that were drilled earlier and align one of them on top of the assembly so that it is flush end-to-end and side-to-side with the assembly and the counter-bevels are facing UP. Use a #10 X 2-1/2” wood screw to set drill points through the center of each of the screw holes into the edges of the construction lumber on the assembly. Drill a 1/8” diameter pilot hole at each of the drill points, then fasten the 1-1/2” X 7-3/16” X 15” piece in place with #10 X 2-1/2” wood screws. Turn the entire assembly over and repeat this procedure with the second 1-1/2” X 7-3/16” X 15” piece of construction lumber. Place the hopper assembly into the top of the mill so that it rests on top of the shields with the 7-3/16” wide sections facing front and back, and the 4-1/4” wide sections facing the sides of the mill. The assembly should fit loosely into the top of the mill. If it is too tight, remove the bottom sets of screws from the 7-3/16” sides of the hopper, mount the hopper on your radial saw table and use a dado to remove 1/16” of material from the thickness of the bottom 3-1/2” of one of the 7-3/16” sides. Re-test the fit and, if still too tight, remove another 1/16” from the opposite 7-3/16” side. Re-install the screws, then replace the hopper assembly into the top of the mill, centered from side to side so that there is a 1-1/2” gap between each of the inboard side surfaces of the frame and the sides of the hopper. Get the two 1-1/2” X 2-1/2” X 7-3/16” pieces of construction lumber and test-fit them into the gaps. Trim as needed to achieve about 1/16” of movement front to back and side to side. Push the pieces down until they are resting snugly on top of the bearing retainers, then draw a line on the hopper assembly along the top of each piece.
Remove the hopper assembly and the loose pieces of construction lumber from the mill. Lay out the two loose pieces as follows - measure and mark a center line on the 2-1/2” side parallel to the length of the piece, then measure and mark drill points on the center line 3/4” in from each end. Drill a 7/32” diameter hole at each drill point, then use a 3/8” diameter drill bit to counter-bevel each hole just enough to fully seat a #10 X 2-1/2” wood screw with the head of the screw flush to the face of the work piece. Align the top edge of one of the loose pieces with the corresponding line drawn on the side of the hopper assembly. Use a #10 X 2-1/2” wood screw
Next, we'll make the catch bin. Get the 9-5/8” X 19-3/8” piece of plywood and lay it out as follows - Draw lines 3/8” in from and parallel to the two 19-3/8” sides. Draw a line 3/8” in from and parallel to one of the 9-5/8” sides, then measure and mark the center point on this line at 4-13/16” from either end. Also measure and mark points 3/4” in from each end of the 9-5/8” line. Starting at the end with the 9-5/8” line, measure and mark points on the 19-3/8” lines at 1-1/2”, 5-1/4”, 9-7/8”, 14-3/8”, and 18-5/8” from the end of the work piece. Drill a 1/8” diameter hole through the plywood at each of the points marked on all three lines. Get the 9-5/8” X 8-5/8” piece of pine plank and lay it flat on the work surface. Now stand the drilled plywood piece up on the drilled 9-5/8” end and align it with one of the 9-5/8” edges of the pine plank. Use a #8 X 3/4" Steel Flat Head Phillips Wood Screw to set drill points into the edge of the plank through each of the three holes drilled at the 9-5/8” end of the plywood. Drill a 1/16” diameter pilot hole at each drill point, then realign the plywood and fasten it in place on the pine plank with #8 X 3/4" Steel Flat Head Phillips Wood Screws. The screw heads should be flush with the surface of the plywood. Set the assembly on the work surface with the plywood part DOWN and the free 9-5/8” edge of the pine plank section pointing UP.
Now get two of the 3/4” X 3/4” X 18-1/2” pieces of pine plank and align them with the 19-3/8” edges of the plywood, with one end butted-up against the pine plank and the other end flush with the free 9-5/8” end of the plywood. Clamp the 3/4” X 3/4” X 18-1/2” pieces of pine plank to the plywood while maintaining alignment. Turn the assembly over and use a #8 wood screw to set drill points into the pine plank sections through the holes in the plywood. Drill a 1/16” diameter pilot hole at each drill point and then fasten the pieces together with a #8 wood screw in each hole. Set the assembly on the work surface so that one 19-3/8” edge of the plywood and the adjoining 8-5/8” edge of the pine plank are DOWN.
Get the two pieces of 8-7/8” X 19-3/8” plywood and lay them out as follows - Designate one 19-3/8” side of each piece as “FRONT”, the opposite 19-3/8” side as “BACK”, and one 8-7/8” end as “BOTTOM”. Draw a line 3/8” in from and parallel to the “FRONT” 19-3/8” sides. Draw a line 1/2” in from and parallel to the “BACK” 19-3/8” sides. Draw a line 3/8” in from and parallel to the “BOTTOM” 8-7/8” ends. Measure and mark the center points on the “BOTTOM” lines at 4-7/16” from either end, and measure and mark points 3/4” in from each end of the 8-7/8” lines. Starting at the “BOTTOM” ends, measure and mark points on the 19-3/8” lines at
Get the remaining two 3/4” X 3/4” X 18-1/2” pieces of pine plank and, one at a time, align them with the edges of the free 19-7/8” sides of the assembly, clamp in place, set drill points, drill pilot holes, and fasten in place with #8 wood screws. Next, get the 11-1/2” X 20” piece of plywood and lay it out as follows - Designate one of the 11-1/2” ends as “BOTTOM”, then draw a line 3/8” in from and parallel to the “BOTTOM” edge, then measure and mark the center point of this line 5-3/4” from either end of the line. Through the center point on the “BOTTOM” line, draw a line parallel to the 20” sides of the work piece. Measure and mark points at 1-3/4” in from each end of the “BOTTOM” line. Draw lines 1-5/8” in from and parallel to each of the 20” sides. Starting at the “BOTTOM”, measure and mark points along the 20” lines at 1-3/4”, 5-1/4”, 10”, 14-1/2”, and 18-3/8” from the “BOTTOM” edge. Drill a 1/8” diameter hole through each point marked on the plywood. Align the plywood piece on the assembly so that the “BOTTOM” of the plywood is flush with the “BOTTOM” edge of the remaining free end of the pine plank section on the assembly, and the 20” sides of the plywood overlap the assembly equally on each side (approximately 3/4” overlap on each side). Clamp in place, set drill points, drill pilot holes into the pine plank sections on the assembly through the holes in the plywood, then fasten the plywood in place with a #8 wood screw in each hole.
Get the Drawer Pull Handles and align one parallel to and centered on the 20” center line on the 11-1/2” X 20” side of the assembly, with the bottom end of the drawer pull 1” UP from the “BOTTOM” of the assembly. Set drill points into the plywood through each of the mounting holes in the drawer pull, select a drill bit at least 1/16” smaller than the mounting screws that came with the drawer pull, and drill pilot holes. Fasten the drawer pull in place with the mounting screws. Align the second drawer pull centered on and perpendicular to the center line on the plywood, about 2” DOWN from the TOP of the assembly. Set drill points, drill pilot holes, and fasten the drawer pull in place with mounting screws. This completes the catch bin.
Next time we'll try to finish this sucker - we'll make the motor mounting bracket, mount the motor, build the power cord & switch assembly and wire it in, and discuss basic operating and safety procedures. Then I intend to take a long rest! You will need a 6" X 10" piece of 1/16" to 3/32” thick Plate Steel, (1) Plastic Single Electrical Workbox, (1) Common Wall Switch (15amp / 125volt) with Cover Plate, (1) Ten foot length of #16 three prong (grounded) Power Cord. See you in two months.
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