How to Build a Workhorse Grain Mill
Some interesting things have occurred since our last installment, interesting in the context of the ancient Chinese curse that goes something like, “May you live in interesting times.” As a result, certain background information given last time around has since been rendered null and void, and we are obligated to set the record straight - Thrifty is no longer associated with a certain business misadventure that shall remain nameless. In deference to anticipated legal actions, we are unable to share the “gristly” details of our disassociation at this time. Instead, needing a therapeutic outlet for pent-up frustration, outrage, and feelings of utter betrayal, Thrifty will channel his indignant energies into his projects. Why, he might even write a book. Yeah, that's it, a book. Pure fiction of course. A sordid, slime-befouled tale about jealousy, egotism, political ambition, fiduciary irresponsibility, gross incompetence, deceit, power tripping, betrayal, disloyalty, ingratitude, hypocrisy, greed, malevolence, despotism, arrogance, negligence, dereliction, conspiracy, character assassination, charlatanism, treachery, misrepresentation, self-absorption, false witness, cowardice, moral and ethical bankruptcy, blatantly aggrandizing self-promotion and an unhealthy overriding addiction to the public spotlight. Wow, all the ingredients for a best-seller! Did I mention betrayal? Any perceived semblance of bitterness in these musings is of course purely coincidental, or the figment of the reader's overactive imagination, and does not represent the viewpoint of any actual persons. But it does have a certain cathartic effect, don't you think?
OK, time to get down to business. We'll start out by building the rollers - the heart and soul of our grain mill. For those who
Now, let's get started. The first step is to cut two six inch lengths from the 18" piece of 3-1/2"OD steel pipe. The end faces of each piece must be as close to square (uniformly perpendicular to the length of the piece) as possible. If you know someone who has access to and knows how to use a metal lathe, then by all means ply them with a little homebrew or your favorite craft beer to have the pieces cut and squared on the lathe and, if possible, knurl the outside cylindrical surface of each piece. If no lathe is available, we'll just have to do it the hard way as follows.
Assume the ends of the pipe stock are not square. Get a piece of paper from a legal pad (8-1/2" X 14") and wrap it lengthwise around the pipe to form a tight paper cylinder 8-1/2" long. Carefully align the overlaps at the top and bottom of the paper cylinder, then use some tape to secure the alignment. Slide one end of the paper cylinder to within 1/4" to 3/8" of the adjoining end of the pipe, then use some tape to secure the opposite end of the paper cylinder to the pipe. Use a scratch awl or a marker to carefully trace along the edge of the paper cylinder to scribe a line around the circumference of the pipe. Remove the tape securing the paper cylinder to the pipe, then slide the cylinder away from the mark just made, leaving about seven inches between the mark and the edge of the cylinder. Measure and mark a point on the pipe exactly six inches from the first mark. Align the edge of the paper cylinder with the second mark, then secure in place with tape as before. Scribe a second line around the pipe along the edge of the cylinder. Repeat this procedure once more so that the pipe is marked with three lines to define two six inch sections of pipe. Remove the paper cylinder, then use a hacksaw to carefully make a shallow cut all the way around the pipe on each line.
Once each line has been permanently established with a shallow cut, saw through the pipe at each line. This can be done fairly quickly if you have access to and know how to use a metal-cutting band saw. Remember that the band saw is equally efficient at removing appendages as it is cutting pipe, so be very careful. The more tedious but safer method is to use the hacksaw. I recommend rotating the pipe 1/4" after every two or three strokes, instead of cutting straight through, to keep the saw from
When the two six inch pieces of pipe have been cut, set the 1/4+" drop-off and the remaining piece of pipe stock aside for use later in the project. Use a file to remove any burrs from the cut ends of each pipe section. Wrap some 3/4" wide masking tape around each end of each pipe section, with the outside edge of the tape aligned exactly on the end of the pipe. One complete turn plus a 2" overlap should do. Select a starting point on each taped end, to be designated as the Zero Degrees location, and place a mark at that starting point and at locations 45 Degrees, 90 Degrees, 135 Degrees, 180 Degrees, 225 Degrees, 270 Degrees, and 315 degrees respectively. Use a square to draw the degree marks on the ends of the pipe and across the width of the tape exactly parallel to the length of the pipe. On each degree line, measure and mark a point on the tape 3/8" in from the end of the pipe. Use a point punch to set a drill point at each of these marks, then drill a 5/32" diameter hole through the pipe at each drill point. After drilling these holes (32 in all - eight on each end of each pipe) use a 5/16" drill bit to carefully counter-bevel each hole just enough so that the head of a #8 X 1-1/4" Steel Flat Head Phillips Wood Screw will be completely below the outside surface of the pipe when fully inserted into the hole. Do not drill any deeper than necessary to seat the screw head fully below the pipe surface. When all 32 holes have been drilled and counter-beveled, use a file to dress off any burrs on both ends (in & out) of each hole.
Next, stand each pipe section on end and use a point punch to set a drill point at each degree mark on the end of the pipe, exactly centered between the inside and outside diameters of the pipe. Turn the pipe sections over and set the drill points on the opposite ends. Use a 3/32” drill bit to drill a hole at each point - these holes must be drilled parallel to the length of the pipe and should just break through into the corresponding holes previously drilled from the side. Use a 3/16” drill bit to slightly (no more than 1/16” deep) counter-bevel each hole. Use a file to dress off any burrs on the ends of the pipe sections.
Now comes the fun part. If you are not one of the fortunate few who have a lathe or a friend who has one, the outside surface of each pipe section will have to be knurled manually. Leaving the masking tape in place, set a pipe section on a shock absorbing surface, such as a piece of carpet, and use a hammer and cold chisel to make "X" marks about 1/32" deep all the way around the outside of the pipe in the area between the taped ends, so that there is no more than 3/32" of space separating any two marks in any direction. Do not chisel mark the area covered by the tape. Unfortunately, this will take quite a while and will drive your family and/or neighbors nuts if they are within earshot. I recommend sending your family to the movies and plying your neighbors with some good beer as needed before starting.
When the knurling is complete, get the 1/4+" drop-off from the pipe cutting operation and use its inside diameter as a pattern to draw four circles on one of the pieces of 2" X 4" lumber, leaving about 1/2" between adjoining circles. Use a square rule to find and mark the center point of each circle, then drill a 5/64” diameter hole through each center point. Use the radial arm saw with a fine-toothed plywood blade to cut between each circle to make four separate work pieces, then cut out each circular piece of wood. CAUTION - this can be extremely dangerous if you are not familiar with the proper techniques for cutting circles with a radial saw, so, if you don't know, GET HELP from someone who does! Otherwise, you may end up needing help of another kind at the emergency room. It is best to use a circle-cutting jig. If you do not have one, you can easily make one as follows: Get a piece of 1/2” or thicker plywood, about one foot by three feet, and use a square rule to find and mark the center point on one side. Drill a 5/64” diameter hole at the center point, then insert a 1-1/2” long X 5/64” diameter nail through the hole. Position the jig board on the saw table with the point of the nail up. Place one of the work pieces on the jig, sliding the hole at its center point down onto the nail. Position the jig board on the saw table so that it is snug against the guide rail and the saw cut is exactly tangent to the circle on the work piece, then clamp the jig board onto the saw table using “C” clamps. Adjust the height of the saw blade so that it will cut through the work piece and about 1/32” into the jig board. To cut out the circle, make a series of cuts, rotating the work piece on the nail a few degrees after each cut. Make each cut slowly to keep the saw blade from grabbing the work piece. It is highly recommended that you do not hold the work piece with your hand - use a piece of scrap wood as a holder so your fingers will still be available to hold your beer glass later. Save the circle jig, you will need it again later in this project.
The resulting wood disks should fit snugly into the ends of the pipe sections - fit one disk at a time, mark the disk and the pipe end with a number so you can match them up again later, and remove the disk before fitting the next (if you don't, both ends of the pipe will be blocked, and it will be difficult to remove the disks without damage). If necessary, use a file and/or sandpaper to remove just enough material to allow the disk to be inserted fully into the pipe end, so that the outer face of the disk is flush with the end of the pipe and there is no wobble in any direction. If any disk is at all loose or wobbly, discard it and make another that fits properly.
As this fit is achieved for each disk, mark the disk by using a straight edge to draw a line across the face of the disk, passing through center point of the disk and extending to the outer rims of the disk. This is the alignment line. After all of the disks have been fitted and marked, they can be mounted in their respective pipe ends as follows. Insert the disk into the matching pipe end so that the alignment line is aligned with any degree mark on the taped pipe end. Circle the degree mark to identify it as the alignment mark. Make sure the face of the disk is flush with the end of the pipe, then drill a 5/64" pilot hole into the wood disk through the center of each 5/32" screw hole in the pipe. After drilling each pilot hole, install a #8 X 1-1/4" Steel Flat Head Phillips Wood Screw, making sure the head of the screw is seated in the counter-bevel and is fully below the outer surface of the pipe.
When all of the disks have been mounted, use a straightedge to draw lines between opposing degree marks across each disk through its center point. Next, get one of the floor flanges and measure its outside diameter. Use this measurement to set a drawing compass. Then draw a circle on the face of each disk, using the center point of the disk as the compass pivot point. Now place the flange on the face of the disk so that the outside edge of the flange is aligned on the circle, and the mounting holes in the flange are centered between the lines drawn across the face of the disk to opposing degree marks. It is important that the mounting holes on the flange should not be on or near any of the degree marks so as to avoid interference with the retaining screws holding the wooden disks in place. When this alignment is achieved, place a mark on the disk at the center of each mounting hole in the flange. Remove the flange, then drill a 3/16" hole through the face of the disk at each of the mounting hole marks - these holes must be drilled perpendicular to the face of the disk! After drilling these holes, thread a #10 X 2" Stove Bolt about half way into one of the holes, remove the #8 retaining screws, and use the Stove Bolt to pull the disk out of the pipe. Remove the Stove Bolt, turn the disk over so that the inside surface of the disk is up, then thread a #10 X 2" Stove Bolt all the way into each hole so that the heads of the bolts are firmly seated against the inside surface of the disk. Reinstall the disk into the pipe, making sure the alignment mark on the pipe is aligned with the alignment line on the disk, and secure with the #8 retaining screws. The two completed pipe and disk assemblies are now the roller barrels.
Get the 1/2"MNPT X 6" long Black Iron Pipe Nipples and use a hacksaw to cut one of the nipples into two sections, one 2" long and one 4” long. Use a file to de-burr the cut end of each pipe section. One at a time, clamp each Floor Flange in a vise and use a pipe wrench to firmly thread one of the pipe sections at least 1/2" into the Flange. You should have two units with 6” nipples mounted, one with the 4” pipe section mounted, and one with the 2” pipe section. After the pipe sections have been mounted on the flanges, use a file to remove about 1/32" off the top of the exposed threads where they protrude from the hub of the Flange, and to remove any irregularities - bumps, seams, etc. - on the unthreaded portion of each pipe section. Do not file the threads on the free ends of the two 6” nipples. Next, drill a 3/32” hole through the side of each flange hub, about half way between any two adjoining flange mounting holes, and centered between the flange face and the end of the hub. After drilling these holes, use a 3/16” drill bit to slightly (no more than 1/16” deep) counter-bevel each hole. Finally, tap a 3/32” roll pin into each hole, leaving at least 1/8” protruding. The four completed flange and pipe assemblies are now the axles for the rollers.
Next, we will mount the axles onto the roller barrels to form roller assemblies. One roller assembly will have one 6” axle and one 4” axle. The other roller assembly will have one 6” axle and one 2” axle. To mount the axles onto a roller barrel, first get the leftover piece of 3-1/2"OD steel pipe and stand it on one end, then support one end of a roller barrel on top of the pipe so that the downward facing end of the roller barrel is aligned with the end of the supporting pipe, and the protruding ends of the stove bolts in the barrel are enclosed by the supporting pipe. Starting with one of the short axles, align the flange of the axle with the circle drawn on the face of the exposed disk on the roller barrel so that each mounting hole is centered on the protruding end of a stove bolt. Install a washer, lock washer and nut finger-tight on the end of each stove bolt, then wrench tighten the nuts 1/4 turn. Invert the roller barrel on the supporting pipe and repeat the above procedure to install the second (longer) axle. The completed unit is now a roller assembly - it should look somewhat like the picture(s)accompanying this article. (In anticipation of complaints due to minor differences between the pictures and what is described herein, DO AS I SAY, NOT AS I DID! I thought of several improvements after I built mine, and was too busy to go back and retrofit.) Repeat the above procedure to make the second roller assembly.
The completed roller assemblies are now ready for rotational alignment. Rotational alignment is necessary to ensure that the crush gap between the rollers will remain uniform during operation. To achieve rotational alignment, the axles must be exactly centered and exactly parallel in relation to the outside surface of the roller. The rotational alignment procedure is a rather painstaking and time consuming trial-and-error process that is best performed using the bearing assemblies that we will be making next time around. So, now you have our agenda for the next issue - building the bearing assemblies and achieving rotational alignment. For that you will need the following materials:
Enough 2” X 4” construction lumber scraps to make (4) 3-3/4” pieces (solid & clear, no knots or cracks!
If all this seems a bit much for you, remember, I did say that this was an advanced project. That comes with the assumption that anyone who decides to build this mill has ample experience in the shop and knows how to use hand and power tools, and therefore does not need quite the detail of instruction as was given for previous projects. This project will span several issues as it is, and I'm guessing it would probably be a good idea to get it done sometime before Halley's Comet returns. Still, if you do feel a compelling need for more detail or clarification, contact Thrifty through the Brewing News and we'll get back to you. Until we meet again.....
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