How to Build a Workhorse Grain Mill
Part 5

Greetings to you hardy individuals who gamely keep coming back for more, risking both sanity and digits, as we continue our quest for the elusive homemade workhorse grain mill! This time around we will construct the main chassis of the mill, into which we will mount those precious roller assemblies you so laboriously and precisely fabricated over what seems like…. errr, I mean, actually was the better part of a year. Look at it this way, it kept you off the streets and out of jail, so it was time well spent. Oh, by the way, it appears that under-zealous editorial oversight resulted in the omission of the gear diagram in the last issue, and I have been assured that it will be included belatedly in this issue. With any luck at all, you should find it in time to keep you from wasting a perfectly good set of gear blanks. My apologies to those who already screwed-up due to this lack of illustration - feel free to direct your complaints to the publisher. Anyway, let's get started before this project has a birthday.

Now to get started with the main chassis. Take two of the 1-1/2” X 10-3/16” X 30” pieces and lay them out as follows - designate one end of each 30” piece as “TOP” and the opposite end as “BOTTOM”, then, designate the LEFT side of one 30” piece as “BACK” and the RIGHT side as “FRONT”. The surface you have been writing these designations on should be designated as “LEFT-OUTBOARD”, then flip the piece over and designate the opposite surface as “LEFT-INBOARD”. On the second 30” piece, designate the LEFT side as “FRONT” and the RIGHT side as “BACK”. The surface you have been writing these designations on should itself be designated as “RIGHT-OUTBOARD”, then flip the piece over and designate the opposite surface as “RIGHT-INBOARD”.
On the OUTBOARD surfaces, draw a line parallel to and 3/4" in from each “FRONT” and “BACK” side. Draw a line parallel to and 3/4" in from each “BOTTOM” end. Draw perpendicular hash marks across each of the “BOTTOM” lines at 3/4" in from each end and at 3-1/2” in from each end. Draw perpendicular hash marks across each of the “FRONT” lines at 3/4", 3-1/2”, 5-3/4” and 8-1/4” down from the “TOP”, and one additional hash mark at 3/4" up from the “BOTTOM”. Draw perpendicular hash marks across each of the “BACK” lines at 3/4", 3-1/2”, 5-3/4”, 8-1/4”, 15” and 22” down from the “TOP”, and one additional hash mark at 3/4" up from the “BOTTOM”. Set a drill point at each hash mark on both 30” pieces, then 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. Turn each 30” piece over so that the INBOARD surface is UP and the counter-beveled ends of the screw holes are facing DOWN. Measure 6-1/4” DOWN from the “TOP” of each piece and draw a line across the work piece parallel to the “TOP”. This line will mark the top edge of the
mounting position for the bearing support blocks, which will be made from two of the 1-1/2”X 1-1/2” X 7” pieces of construction lumber a little later.

Now we get to start putting some of the pieces together. Get the third 30” piece, the one that has not been marked or drilled, and lay it down on a smooth and level work surface large enough to support the entire piece with at least four inches to spare on all sides - the floor will work just fine if your workbench is too small or is covered with junk from other projects the way mine is. Designate the surface facing upward as “BACK-INBOARD”. Now take the two 30” pieces that have just been prepared and set them with the “BACK” edges DOWN and the “TOP” ends both facing in the same direction on either side of the third undrilled 30” piece. Align the drilled pieces so that the “TOP” and “BOTTOM” ends are flush with the ends of the undrilled piece, and designate the ends of the undrilled piece as “TOP” and “BOTTOM” accordingly. Insert a #10 X 2-1/2” wood screw into each of the holes drilled along the “BACK” edges of the drilled pieces and tap with a hammer to set drill points into the edges of the undrilled “BACK” piece. Remove the screws and separate the pieces, then use a 1/8” diameter drill bit to drill a pilot hole at each of the drill points. Now realign the pieces and fasten them together securely with the #10 X 2-1/2” wood screws.

Get one of the 1-1/2” X 10-3/16” X 9” pieces and place it flat on the work surface. Designate the surface facing upward as “FRONT-INBOARD”. Designate one 10-3/16” edge as “TOP”. Now take the assembly made from the three 30” pieces and align it with the 9” piece so that the “TOP” of the assembly is flush with the “TOP” of the 9” piece and the “FRONT” of the assembly is snug against the 9” edges of the 9” piece. Insert a #10 X 2-1/2” wood screw into each of the holes drilled along the “FRONT” edges of the assembly and tap with a hammer to set drill points into the edges of the 9” piece. Remove the screws and separate the assembly from the 9” piece, then use a 1/8” diameter drill bit to drill a pilot hole at each of the drill points. Now realign the assembly with the 9” piece and fasten them together securely with the #10 X 2-1/2” wood screws.

Get the remaining 1-1/2” X 10-3/16” X 9” piece and place it flat on the work surface. Designate the surface facing upward as “BOTTOM-INBOARD”. Designate one 10-3/16” edge as “BACK”. Now stand the assembly on its “BOTTOM” end and align it over the 9” piece so that the “BACK” edge of the 9” piece is snug against the “BACK-INBOARD” surface of the assembly, and its 9” sides are snug against the “LEFT-INBOARD” and “RIGHT-INBOARD” surfaces of the assembly respectively. Repeat the drill point setting and pilot hole drilling procedures as above, then realign and fasten securely with #10 X 2-1/2” wood screws.

Now get the two 1-1/2” X 3-1/2” X 18” pieces and lay them out as follows - lay them on the work surface with one of the 3-1/2” sides DOWN. Designate one end of each piece as “FRONT”, and designate the 3-1/2” side facing UP as “BOTTOM”. Measure 3/4" in from each 18” edge and mark points at each end of each piece. Draw through pairs of points to form lines parallel to the 18” edges. Orient the pieces on the work surface side-by-side with the “FRONT” ends pointing away from you. Designate the left edge of the left piece as “LEFT-OUTBOARD”, and the right edge of the right piece as “RIGHT-OUTBOARD”. Take the piece marked “LEFT-OUTBOARD” and measure and mark a point on the leftmost parallel line 9” from the “FRONT” end of the piece, then measure and mark a point on the rightmost parallel line 7-1/2” from the “FRONT” end of the piece. The second piece, marked “RIGHT-OUTBOARD”, will be laid out in mirror image of the first piece - measure and mark a point on the rightmost parallel line 9” from the “FRONT” end of the piece, then measure and mark a point on the leftmost parallel line 7-1/2” from the “FRONT” end of the piece. Set drill points and drill a 7/32” diameter hole at each 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.

Turn the chassis assembly upside down so that it is standing on its “TOP” end and the “FRONT” side is facing away from you. Align the 18” piece marked “LEFT-OUTBOARD” with the “BOTTOM” side facing UP and the “FRONT” edge flush with the “FRONT” of the chassis assembly. The “LEFT-OUTBOARD” edge of the 18” piece should also be aligned parallel and flush with the “LEFT-OUTBOARD” side of the assembly. Use a #10 X 2-1/2” wood screw to set drill points through the screw holes, then use a 1/8” diameter drill bit to drill a pilot hole at each of the drill points. Realign and fasten together securely with #10 X 2-1/2” wood screws.
Repeat this procedure to align the “RIGHT-OUTBOARD” 18” piece with the “RIGHT-OUTBOARD” side of the chassis, drill pilot holes, and fasten in place. You can now mount the casters on the bottoms of the 18” pieces as follows - exact alignment is not necessary with swivel casters, but they should be positioned with one set of adjacent mounting holes approximately 3/4" to 1” in from each end of each 18” piece, and approximately centered from side-to-side. Mark a drill point in the center of each mounting hole,
then use a 1/8” diameter drill bit to drill a pilot hole at each of the drill points. The casters at the “FRONT” of the chassis should be secured with #10 X 2-1/2” wood screws, which will penetrate all the way through the 18” pieces and into the “BOTTOM” of the chassis. The casters at the “BACK” of the chassis should be secured with #10 X 1” wood screws. Return the chassis assembly to
an upright position.

Get two of the 1-1/2”X 1-1/2” X 7” pieces and set them on a work surface with the grain running parallel to the work surface - you should be able to see the grain when looking at the piece from the side. Layout the top of each piece as follows - measure and mark points on the top of each piece, 3/4" in from each end and each side, hash mark each point, and then draw a centerline parallel to the 7” length of each piece. Measure and hash mark a third point on the centerline 3-1/2” in from either end of each piece, then set a drill point at each hash mark and drill a 7/32” diameter hole - 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. These pieces are the bearing support blocks. Lay the chassis assembly on one of its sides (NOT the FRONT or BACK!). Take one of the bearing support blocks and align it with the mounting line drawn on the INBOARD side of the chassis assembly (presently facing UP). The counter-beveled ends of the screw holes in the support block should be facing UP. Center the support block between the FRONT and BACK sides of the chassis - there should be about 1/8” clearance on each end of the block. Use a #10 X 2-1/2” wood screw to set drill points through each of the three screw holes in the support block. Mount a 1/8” diameter drill bit in a spare chuck (or remove the chuck from your drill if you don't have a spare) and carefully drill pilot holes BY HAND (I'm betting your drill won't fit inside the chassis, mine didn't!). Realign the support block and fasten securely with #10 X 2-1/2” wood screws. Turn the chassis over and repeat this procedure to mount the second support block. Return the chassis assembly to an upright position.

For this next part you will need one of the bearing assemblies from the rollers you built way back when (You remember the rollers, don't you? You know, those things you spent a gajillion hours painstakingly coaxing into rotational alignment!). Anyway, take one of the bearing assemblies off of a roller and position it on the bearing support block on the RIGHT side of the chassis. The oil hole in the bearing assembly should be facing UP, and the bearing assembly should be flush with both the RIGHT side and FRONT inboard surfaces of the chassis. The oil hole is conveniently located at the center of the top of the bearing assembly, so it can be used to locate a reference mark on the RIGHT side inboard surface of the chassis. Also use a pencil to scribe a mark on the RIGHT side inboard surface of the chassis at the bottom of the INSIDE of the bearing. This mark defines the lowest point at which the axle of the roller will penetrate the side of the chassis. Now reposition the bearing assembly so it is flush with the BACK inboard surface of the chassis, and make another set of reference marks on the RIGHT side inboard surface of the chassis. Remove the bearing assembly and reposition it onto the bearing support block on the LEFT side of the chassis, flush with the BACK inboard surface of the chassis. Make another set of reference marks on the LEFT side inboard surface of the chassis. Remove the bearing assembly and reassemble it to its roller. Use a square rule to draw lines, perpendicular to the TOP edge of the chassis, from the corresponding lowest point mark through each of the oil hole reference marks to the corresponding TOP edge of the chassis, then perpendicular across the TOP edge of the chassis, then perpendicular down the corresponding OUTBOARD surface of the chassis to a depth of about 10 inches. Measure the distance from the TOP edge of the chassis to a lowest point mark on the INBOARD surface of the chassis. Then mark the corresponding point on the OUTBOARD surface. Repeat for each set of reference marks. There should now be three reference marks on the OUTBOARD surfaces, one at LEFT REAR, one at RIGHT REAR and one at RIGHT FRONT.
Measure and mark drill points 3/8” UP from the OUTBOARD reference marks at RIGHT REAR and LEFT REAR. Use a 1” spade
drill bit to drill a hole through the side of the chassis at each drill point, perpendicular to the side of the chassis. Measure and mark a drill point 9/16” UP from the reference mark at RIGHT FRONT, then use a 1-3/8” spade drill bit to drill a hole through the side of the chassis at that drill point, perpendicular to the side of the chassis. Use a square rule to draw lines perpendicular to the TOP edge
of the chassis, tangent to the circumference of each of the 1” and 1-3/8” holes. Use a saber-saw with a fine tooth blade to carefully saw along each of the lines until they just intersect the circumference of the corresponding holes. Mark the resulting cut-outs to
match them to the slots they came out of and set them aside, you will need them later. Install the roller assemblies into the chassis
as follows - the roller assembly with the drive pulley is installed in the REAR position with the drive pulley on the LEFT and the gear
on the RIGHT with the axels nested into the slots in the sides of the chassis, and the other, shorter roller assembly is installed in
the FRONT position with the short axle on the LEFT and the gear on the RIGHT with the RIGHT axel nested in its slot in the side
of the chassis.

We'll take a short break from carpentry to make a pair of bearing grain/dust shields out of sheet metal. The shields are needed for the next step because they play a role in the positioning of the bearing retainer blocks. Get your supply of galvanized furnace duct material and use a pair of tin snips to cut out two pieces 7-3/16” long by 3” wide. Trim off about 1/8” of the point at each corner, then use a fine file to remove burrs and sharp edges all the way around each piece. Measure and mark a centerline parallel to the 7-3-16” length of each piece, then mount each piece one at a time in a vise with the centerline clamped precisely on the top edge of the vise jaws. Now carefully bend the piece very slightly at the centerline so that there is about 1/16” to 3/32” of displacement from vertical at the free edge of the piece. The finished shields should look like very low-profile roofs with 1/16” to 3/32” peaks. Install the finished shields onto the bearing assemblies - one on top of the pair of bearing assemblies on the RIGHT ends of the rollers, and the other on top of the bearing assemblies on the LEFT ends of the rollers.

Next we will make the bearing retainer blocks. Get the remaining pair of 1-1/2”X 1-1/2” X 7” pieces of construction lumber and set them on a work surface with the grain running parallel to the work surface - you should be able to see the grain when looking at the piece from the side. Layout the top of each piece as follows - measure and mark points on the top of each piece, 1" in from each end and 3/4” in from each side, and then draw a centerline through the two points parallel to the 7” length of each piece. Drill a 9/32” diameter hole through each point, perpendicular to the surface of the piece. Designate the laid-out surface of one piece as “RIGHT-INBOARD”, and designate the laid-out surface of the other piece as “LEFT-INBOARD”.

Set the “RIGHT” bearing retainer block on top of the grain/dust shield on the pair of bearing assemblies on the RIGHT ends of the rollers, with the “RIGHT-INBOARD” surface facing AWAY from the “RIGHT-INBOARD” surface of the chassis. Set the “LEFT” bearing retainer block on top of the shield on the bearing assemblies on the LEFT ends of the rollers, with the “LEFT-INBOARD” surface facing AWAY from the “LEFT-INBOARD” surface of the chassis. Designate the upward facing surfaces of the retainers as “TOP”. Center the retainer blocks between the FRONT and BACK sides of the chassis - there should be about 1/8” clearance on each end of a block. Push DOWN hard on each bearing retainer and use a pencil to mark points on the INBOARD LEFT and INBOARD RIGHT sides of the chassis at the center of each 9/32” hole in the bearing retainers. Remove the retainer blocks, hash mark the hole center points, and use a square rule to draw lines, perpendicular to the TOP edge of the chassis, from each of the hole center points to the TOP edge of the chassis, then perpendicular across the TOP edge of the chassis, then perpendicular down the corresponding OUTBOARD surface of the chassis to a depth of about 6”. Measure the distance from the TOP edge of the chassis to each of the hole center points on the INBOARD surface of the chassis, then mark the corresponding points on the OUTBOARD surface. Drill a 9/32” diameter hole through each point, perpendicular to the surface of the chassis.

Retrieve the bearing retainers and install a 1/4"-20 Steel Tee Nut into each hole on the INBOARD surfaces of the retainers. Reposition the retainers in their respective positions on the grain/dust shields, TOP surfaces facing UP and INBOARD surfaces facing AWAY from the corresponding INBOARD chassis surfaces. From the OUTBOARD chassis surfaces, install a 1/4"-20 X 3" Steel Hex Head Cap Screw with matching Washer into each 9/32” hole and thread it into the corresponding Tee Nut in the bearing retainer. Push DOWN hard on each bearing retainer and tighten the 1/4"-20 X 3" Steel Hex Head Cap Screws to secure the bearing retainers in place. Retrieve the pieces that were cut out to make the axel slots in the sides of the chassis. One at a time, place the cutouts into their corresponding axel slots and hold the cutout so that its TOP edge is exactly even with and parallel to the TOP edge of the chassis. Draw a line across the INBOARD surface of the cutout along the TOP edge of the bearing retainer. Remove the cutout and measure and mark a point 3/4” DOWN from the line just drawn, and centered from side to side on the cutout. Drill a 7/32” hole through the cut-out, perpendicular to the surface of the cut-out. Turn the cutout over so that the OUTBOARD surface is UP, and use a 3/8” diameter drill bit to counter-bevel the 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. Reposition the cutout in its corresponding axel slot, keeping the TOP edge even and parallel with the TOP edge of the chassis, and use a #10 X 2-1/2” wood screw to mark a drill point on the OUTBOARD surface of the bearing retainer. Remove the cut-out, drill a 1/8” diameter pilot hole at the drill point on the bearing retainer, then reposition the cutout and secure in place with a #10 X 2-1/2” wood screw.

Remove the bearing retainers and dismount the FRONT roller assembly. Set the assembly on a flat work surface with the oil holes in the bearing blocks facing AWAY from you and the FRONT surfaces of the bearing blocks facing UP. Draw diagonal, corner to corner lines on the FRONT surfaces of the bearing blocks so that the resulting “X” crosses at the center-point of the surface. Use a square rule to draw lines through the center-point, one parallel to the 3-1/2” length, and one across the 1-1/2” width of the bearing block, then extend those lines about 1/2” onto the INBOARD and TOP surfaces of the bearing block. These lines define the center-point of the FRONT surface of the bearing block from the TOP and INBOARD surfaces respectively. Carefully drill a 3/32” diameter hole 3/4” deep at the center-point and perpendicular to the surface of the bearing block. Now tap a 1/8” X 3/4” long Broad-headed Roofing Nail into the hole.

Remount the roller assembly, but do not install the bearing retainers. Press the bearing blocks firmly against the INBOARD surfaces of the chassis, then mark the INBOARD surfaces of the chassis at the center-point definition lines on the bearing blocks. Dismount the roller assembly again and use a square rule to transfer the center-point definition mark taken from the TOP of the RIGHT bearing block to the TOP-FRONT of the chassis, then measure and record the distance from the RIGHT-OUTBOARD surface of the chassis to the definition mark. Now measure and record the distance from the TOP-FRONT of the chassis to the center-point definition mark taken from the INBOARD surface of the bearing block. Use the recorded distances to measure and mark a drill point on the FRONT surface of the chassis, corresponding to the center-point on the RIGHT-FRONT bearing block. Repeat this procedure for the measurements taken from the LEFT-FRONT bearing block. Drill 9/32” holes through the FRONT of the chassis at each drill point. Now install a 1/4"-20 Steel Tee Nut into each of the holes from the INBOARD surface of the chassis. Thread two 1/4”-20 Steel Hex Nuts all the way onto each of the remaining 1/4"-20 X 3" Steel Hex Head Cap Screws, slide a washer onto each screw, then insert a screw into each of the holes in the FRONT of the chassis and thread them into the Tee Nuts - make sure the screws do not protrude from the INBOARD surface of the chassis. These screws, together with shims between the FRONT and BACK bearing blocks, will lock the rollers in place to maintain the desired crush gap. Remount the FRONT roller assembly.

OK, we're done for this issue - to be continued next time! In the mean time, you can experiment with making shims to go between the bearing blocks - any thin, non-compressible material, such as sheet metal, plastic, or even card stock, that can be cut to size to match the ends of the bearing blocks will do. You will need enough shims to build-up to the various crush gaps you may need to use for different grains (two-row, six-row, wheat, rye, etc.). Next time we will deal with the grain hopper, the catch bin, and mounting the motor. See ya then!

Your stubbornly stingy do-it-yourselfer,
The Thrifty Gadgeteer

Continue to Part 6
Return to Part 4
Return to Index


Copyright 2008, Great Lakes Brewing News

Brewing News - America's Regional Craft & Home Brew Newspapers