DIY 2" x 72" Belt Grinder Project

Wish List

2 x 72" belts

1.5 to 3 horsepower

Variable speed

Removable attachments, platen and contact wheel

Variations

Procurement





Construction





























































































Tracking and Tensioning Pillar





The Platen Attachment

















UPDATE:

As some have mentioned, the 12 x 3" platen plate has limited space on the left side of the platen around the tool arm itself. One can grind above or below the centre, but when using a grinding jig on a fixed work rest the tool arm can get in the way. A slightly longer (and recommended) plate are shown below.









This 12 x 4 plate offers better access to the platen on the left side near the centre of the platen. This deeper plate will give an extra inch clearance in this area. The arc radius is the same, however the platen mounting is reduced to two points which works just fine.





















I wanted to point you to Chris Fall's three part video build on YouTube. Chris uses slightly different materials, but his videos are great for showing the basic construction of his version of the BG-272.









































VFD Power Wiring





Operator's Control Panel

VFD Enclosure

Tying it all Together









Running The Grinder

Grinder Stand

Small Wheel Attachment

10" Contact Wheel Attachment

Like almost every newbie knifemaker owning a decent belt grinder is dream. When I realized the price of a machine, my jaw hit the floor. Most of us getting started cannot afford a $2000 grinder. So I set out to design my own and I shamelessly borrowed as many ideas as I could. One special shout out to Alaskabearhawk for his great design and detailed videos on YouTube. If you are not sure about making this grinder, there is well made and very reasonable Ready to go grinder based on my plans. My wish list for my new grinder would be:Before building I considered some variations:Stepped sheaves for varying speed. This would be a lower cost build, but still allow some speed changing. I would need two pillow blocks, an axle and a stepped sheaves (or pulleys as some folks call them). The drive wheel could be 4" diameter still. This arrangement would let me use any motor, whether it can be reversed or not.Fixed speed would be lowest cost and simplest build as there are less components and less alignment issues. The motor can be 2 pole or 4 pole and must be rotating in the CCW direction. That's fairly easy. Drive wheel size becomes a focus. For a 1800 RPM (4 pole) motor I'd use a 5" or 6" wheel. 2335 or 2826 surface feet per minute. For a 3600 RPM (2 pole) motor I'd use a 3" or 4" wheel. 2826 or 3768 surface feet per minute.To get the surface feet per minute, use the formula:(Motor Speed in RPM x 3.14 x Wheel Diameter) / 12.Take a look at some of the other builds on the BG-272 Gallery of Builds page . Some very clever ideas going on there. Thanks to all that sent in photos and made such great suggestions. The search for suitable wheels proved fruitless as the most common maker in the US did not ship to Canada at the time. I found these wheels from Europe on eBay. You may want to check out Origin Blade Maker's belt grinder wheel set Note: If you want to machine your own wheels, here is a PDF and a CAD drawing graciously provided by K. Langeveld.For the drive wheel, I am using a 4" nylon caster that is 2" wide. I had to push the roller bearing race out and insert a shim with a 7/8" inside diameter. I then had to cut a key way for the 3/16" key stock. A fair bit of work, but I have made what is effectively a sub $20 crowned drive wheel.The motor came from an ad on Kijiji . I scored this 2 horsepower T145C face motor, 3 phase 230/460V for a whopping $35. I wasn't too sure about this but after a quick ohm meter test and a spin of the shaft I think we're going to be fine.For the variable speed part, I chose a Yaskawa J1000 VFD. My work associations with Yaskawa have been top notch over the years and basic shaft spinner came into my hands at a very reasonable price.I am going to install the VFD in a sealed enclosure (NEMA 4) and wire a control panel for the operator to start, stop and vary the speed of the motor from the front of the grinder.For the basic electrical I sourced from eBay, Digi-Key and my locals like Home Depot, Canadian Tire and Peavey Mart.Not everyone can chance upon a nearly free motor. I have made a Belt Grinder Motor Guide to help you in selecting a motor. Aside from a few electrical things, remember to check the shaft size on the motor and make sure the drive wheel's bore is a match. Drive wheels usually come with 5/8", 3/4" or 7/8" bores.The basic construction is of HSS (Hollow Structural Steel) pieces and some plate and scrap pieces from my shop and from Metal Supermarket. The pieces I cut on a band saw so they are nice and square.I bought 48" of 2" HSS, 0.188 wall and cut them like this.You must remove the seam inside the 2" HSS receivers before any welding takes place. This seam will prevent the inserted 1-1/2" tubing from sitting square inside their receiver. Use a long file or a small grinder wheel in a drill with an extension and remove the seam. Once the frame is welded, it becomes much more difficult to do this with a file.As suggested by Ken DeRosier, make sure the welded seams are positioned on the left (where the lock down nuts will be installed.) This reduces the seams from being an issue, and provides a perfectly flat face for the tool arm to rest against.Pieces A, B, C and D are squared, clamped and welded to make a frame like this.I drilled some holes and tacked some 3/8" NC nuts for the lock downs. I then welded the frame to a 12" x 20" plate of 1/4" steel, again checking for squareness and clamping everything in place before tacking.I added four 1/4" x 1-1/2" studs for mounting the motor. These are flat head capscrews and I countersunk the underside so that they didn't stick out. I used hex nuts and placed fender washers on to support the motor. These being a bit smaller than the motor foot mount holes, allows for some rotating of the motor to get the belt to track properly. Also a 6" piece of strut to mount the operator control panel. The motor is positioned so that the center of the shaft is about 4" to the back of the vertical receiver.30 pound spring. Thanks Dave! I measured this on a scale. Pressing down on the spring about 30 pounds caused it to deflect 1". More recently, we have found that springs from screen door chains will work okay. Update March 2017. I have made some better drawings of the frame.The tracking and tensioning pillar slips into the upright receiver part C of our frame and sits on top of the spring. It has a tracking hinge that can be adjusted to tilt the tracking wheel.The hinge part has a hole drilled right through, 3/4" from the top and 1-1/8" from the right side as shown. This hole must be offset from center to allow for the axle to go both positive and negative camber. This hole is slightly larger than the 1/4" bolt that will act as the hinge pin.The axle hole is 2" from the top, centered.The pillar itself is 13" long. This may have to change depending on the spring that you have available. My spring is about 4" long, so add or subtract a little if your spring is shorter or longer.The axle hole is 3/4" from the top and centered on the 1-1/2" pillar and is drilled right through. A drill press works well to keep this hole straight when drilling through. See photos below for construction.The cutout hole for the tracking wheel axle is 2" from the top of the pillar so that the head of the axle bolt goes inside of this cutout. If you use a carriage head bolt for the axle, you need only make a round hole. I clamped the hinge with shims around it before drilling a pilot hole right through both pieces on the drill press. Add 1/16" shims on the sides and 1/8" on the face.I tacked a flat washer on either side then hit them with the belt to thin them down to a good friction fit inside the hinge piece. The pillar will need an area removed for the bolt head of the tracking wheel axle to come through. If you were to use a carriage head bolt, this could be a circle. I had no luck finding a 12 mm carriage head, so I made a square to fit the hex head of the bolt.Test fitting the hinge.The top and bottom of the pillar get capped with some 1/8" flat bar. Before tacking the top plate in, I drilled and inserted 5/16" x 1" bolt, then tacked that around the head. This will be for my shifter ball. (The ball will make it easier to push the pillar down.)Also note the 1/4" nut mounted for the tracking adjustment knob. The bolt going through here will press against the tracking wheel axle bolt and allow the tilt of the hinge to be adjusted.The platen attachment slide into a receiver and is locked in place. The tool arm is of 1-1/2" HSS with 0.250" wall that is 17" long. The plate that the wheels attach to is 3" x 12" made of 3/16" steel. I set the holes 10-3/8" apart so as to leave a good amount of space between them for a 9" platen. The platen is made from a piece of 2" angle iron. The angle is 0.188" thick.I put a backing piece of 1/4" plate behind the angle to step it away from the plate. This could be accomplished with a small stack of flat washers as well. This space is to bring the platen directly in line with the belt and wheels. If you need to tweak the platen to the left or right, add or remove a washer from three bolts securing the platen to the plate.The wheels are mounted typically with 1/2" bolts. In my case I have metric wheel bearings, so 12 mm bolts. The wheels cannot run against the plate, so I made some spacers from schedule 40 3/8" pipe cut into short sections about 1/4" and with a hacksaw and shaped with a file to uniform thickness of close to 3/16". Slip the spacer over the bolt, slide the wheel on and the inner race should be kissing the spacer.Below are some updated drawings for the flat platen.Tilt adjustment is made by loosening the two bolts and and adjusting. Once in the correct angle, lock the plate in place with the two bolts.For the work rest, a found a piece of 1/4" thick plate about 4" x 6" and welded a piece of 3/8" x 3/4" bar stock to it. I drilled and made two slots for the 1/4" NC socket head capscrews to secure to the bottom of the tool arm.Note that this work rest has been replaced with the Adjustable Work Rest Test fitting and tracking evaluation. Before painting, I added a 1/4" x 1/2" bolt on the vertical piece so I could mount a brush to remove static charge from the belt.One thing to note here. The pillar is a little bit loose inside the vertical receiver. I added two strips of plastic (from an old oil jug) to act as shims. These are dusted with a little graphite to make them slippery.Unit painted.Added the tool rest made of 1/4" plate on a 1/2" x 3/4" flat bar mounted to the underside of the platen tubing with 2 tapped 1/4" holes and hex socket capscrews to match.Powered up the motor for live tracking test and VFD programming.Grabbed two extension cords from different plugs in the garage and made 240V. A little high but should be ok. See the section on VFDs if you want to source 240V.Powered up the VFD for initial programming.The VFD requires a 240V / 20A supply. I have opted for a NEMA L6-20 receptacle and plug. The L means 'Locking' and this will assist in preventing any accidental un-plugging of said plug. I am using some supple SOOW 3 conductor #12 AWG for the input connection. I'd like some length so I piked up about 15 feet of this. Inside my VFD enclosure I have two midget type fuses that protect the VFD proper. A low current takeoff of 240V for the DC power supply is done immediately after the fusing. For convenience I've added some surplus terminal blocks mounted on DIN rail. The output of the VFD is rated for 10A (three phase) so I used some 4 conductor #14 AWG SOOW (cab tire) cable.To control the VFD I am going to bring out the sequence inputs SC, S1, S3 and S5. This will allow me to START and STOP the motor as well as change the direction FWD and REV. I will also wire in the VFDs status contacts to drive two LEDs indicating motor on and off. Finally, I have a digital tachometer that will count pulses from a small magnet placed in the side of the drive wheel. The net result is that the operator's control panel will look something like this.The magnetic (Hall effect IC) sensor that picks up magnetic field from the small magnet inserted into the drive wheel.When the magnet passes close to the sensor the sensor switches to make a 24 VDC pulse going to the tachometer. This will count the revolutions per minute of the drive wheel.To install the magnet in the drive wheel I drilled a 3/8" hole about 1/4" deep. Put a small daub of epoxy and pressed the magnet in with a vise.The Hall effect sensor is mounted on the C-face of the motor and positioned about 1/4" away from the wheel so that the magnet passes near it each revolution.Drilling the holes to get the jig saw blade in.Masked off the face for drilling, jig sawing and filing the various cut out shapes.Test fitting the tach.Control and tachometer cables with strain reliefs in back of operator control panel enclosure. For the cable, I found some old-school 25 pin printer cable that has an overall shield.Once the VFD enclosure was mounted to the frame, I could terminate one end of the control cable accurately estimate the cable length for the motor. The control wiring is fairly straight forward. One thing to pay attention to is the wire colours. The particular printer cable I had has insulation that is colored solid and some with white stripes. These can be easy to mix up. A quick check put with the ohmmeter will save the day and prevent a mistake here.I ended up with multiple wires going to +24V and common. I used some small wire nuts (Marettes), twisted all the +24V wires and cranked a wire nut on. As the LEDs already had wire leads on them I did solder splices and covered with some 1/8" heat shrink.The VFD enclosure is a surplus Hoffman NEMA 4 14" x 18" x 8". As it did not come with a mounting pan, I had to make one from something. Conveniently, I found some 1/8" utility grade aluminum that was pretty scratched up, but the price (free) was right.I mounted the VFD and 24V power supply as well as some DIN rail to mount the terminal blocks.For strain reliefs I used some nylon domed strain reliefs and one Heyco straight-thru for the tachometer sensor cable.With the incoming power cord attached and the 4 wire motor lead connected it was a matter of programming the VFD to accept the 0-10V input (potentiometer) as the speed command and setting the top frequency to 80 Hz. I also set the acceleration time to 5 seconds and deceleration to 2 seconds.The first run with the unit complete involved a little tweak in the tracking hinge. The belt ran fairly true and didn't walk off the wheels at 4500 RPM.I took a chew through some 154CM and the blaze belt eats it like butter. I am so impressed I will toss my hacksaw out!The stand will hold the VFD enclosure and the grinder will be mounted on the top. For this I chose some scrap channel I had and welded it up. Adding two casters on the rear will allow easier moving, but only when tilting.Before painting this space-ship silver, I welded some 5/16" x 1" flat head bolts to act as mounting studs for the grinder base.Knowing where the motor and VFD enclosure line up, I can drill some holes for some chase nipples to pass the motor cable and control cable through the grinder base plate.July 8, 2014 - Small Wheel Attachment is now here October 2014 - 10" Contact Wheel Attachment is now here Always updating. I will keep you posted.Updated November 2019Dan