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Bob Engnath on Grinders

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This information is supplied by Blades `N' Stuff, a knifemakers' supply outfit in Glendale, CA. We normally offer all of this in our sales catalog. A friend offered to put the useful parts on the net, for all to use without having to send the five dollars that we charge for the catalog.

We aren't here to provide a really neat and exciting web site with a whole bunch of trick stuff. This is pure text information and just about every bit of it is useful to the knifemaker.

Our specialty is working with new knifemakers. We sell pre-ground blades, and this information is specifically aimed at how to finish those blades. Much of it will be useful in other areas, and with your own projects. This is not a complete FAQ on knifemaking. Through the years, we have added bits and pieces of information to the catalog as we found recurring questions from customers. This is also not the last word on any subject mentioned. there are many other methods of doing just about everything mentioned.

If you find the pages interesting, and wish to get our catalog, we are at 1019 E. Palmer Ave, Glendale, CA 91205. Phone 818 956-5110, fax 818 956-5110. No exceptions to the $5.00 price.

We mention the names of a lot of knifemakers in this text. This does not imply endorsement by them. We are merely trying to give credit for a source of information.




(These will also work with many other belt grinders.)

Keep a water bucket on some sort of stand, right under the grinding area, either platen or wheel. It'll catch about two thirds of the dust and grit that would otherwise be spread around the shop. Then, put a hearty dollop of dish washing liquid in your quench bucket. It'll keep the grit from floating on the surface and contaminating your blade when you're doing the final polishing sequence. Don't throw the contents of the bucket into your garden.

Flat grinding goes a lot easier when you grind the platen about 3/32" narrower than the belt and round the edges with a 1/16" radius. This helps keep the belt from snagging and gives a "softer" edge for working into the plunge cuts.

If you have trouble lining up the plunge cuts, try bracing one finger against the side of the platen support to help you hold steady and cut more precisely. Feel the flat of the bevel you've ground by touching the blade to the belt farther up on the portion which is already correctly ground, first. Then, when you have the right angle, go ahead and make the plunge cut.

When you hollow grind and are plagued with a 2" mark on your blades, put a fairly large crown on the contact wheel. It lets you work the corner of the wheel that you need without touching on the opposite corner that you don't need, avoiding the mark. A large crown would be .0075 or less.

Serrated wheels of 90 Duro are handy, but only for really heavy grinding like cutting out patterns. The vibration and noise make them less than great for anything else - BUT - they'll give you give you 30% more from a belt on cut outs.

Your tracking adjustment slot (Burr King) collects a lot of dust which will very shortly keep it from adjusting at all. Replace the existing washer with a larger "fender" type washer to keep out the crud.

The platen will get fairly thin after a dozen or so facings or re-grindings to flatten it. Fender washers are great shims to push it back out to touch the belt again. Just put a couple on each bolt between the platen and its' mount. You'll need new bolts. I'm not going to use a hard chrome plated platen until they stop putting stray bits of grit on the back of the belt. (Facings - that's when you take the platen off and grind the hollows out with the spare). Always have a spare platen, work rest arm and main arbor. They're the parts that always need to be replaced at the start of a four day weekend. The arbor doesn't wear out, but rather wears down. After running the knife maker and work rest arms on and off a few hundred times, the arbor wears down to the point where the arms won't clamp tight any more.

Some fellows have been using a platen faced with high strength glass in an attempt to get better flat finishing. Results are mixed, but promising.

Always be sure the top of the platen has a gentle taper, rounded to give the belt a smooth transition onto the platen. A crisp, sharp top will peel the belt joint apart in no time at all.

The one horse power standard machine is an excellent unit, but some of us find it slightly under powered for production style grinding. A Baldor VL3515 motor is a bolt on replacement, 2 horsepower, 3450 R.P.M., 220V single phase. It'll cut 30% faster and get you 25% more work out of a belt, BUT - it definitely spoils the machine for any sort of finish work. Be sure to order the motor with a switch and base - they're both extra. The motor costs around $250-$300, depending on your dealer. ( There are a few specially ordered bargain Burr King machines out there with a one horsepower VARIABLE motor. Fine for light duty, but way underpowered for any sort of normal grinding. Not a bargain.)

If you have the option, run finer belts at slower speeds. They'll cut smoother and last a LOT longer.

Lining up the work rests' little table to cut "square" to the wheel can be a real pain. Try this. Loosen the set screw so you can just twist the rest with a pliers. Lay a length of bar steel on edge, atop the rest and down alongside the wheel. Hold it firmly, with the edge flat on the rest and then twist the rest until the bars' lower edge lines up 1/8" below the center of the arbor shaft at the wheels center. Tighten the work rest set screw and it'll cut nicely true. If you're lazy. like I am, just use a bowie blank to give the outermost edge of the work rest a whack, up or down, for a quick adjustment.

Work rest tables tend to wear along the inside edge, next to the wheel, allowing the work to rock and get out of "square". You're rubbing relatively hard steel across the work rest, just like a file. The work rest has to be ground flat regularly.

Keep the allen wrenches and the socket you need for changing set-ups where you can reach them without looking around the whole shop, before changing things around. Saves time and frustration. Threaten the brother in law or the kids if necessary.

Cutting the plunge from flat into bevels can be a challenge. Leave the final trim and adjustments in this area for the medium grit finishing belt. Roughing belts are often too aggressive and difficult to control in this area.

When using finishing belts, and especially when slack belting, kill the very edge with a sharpening stick (crock stick) so it won't dig into the plunge cut when you had hoped it would roll back over the edge of platen or wheel to fit that area. Micron film belts are really a problem unless you perform this trick. Killing the edge will not stop it from slicing into fingers.

Speaking of the micron belts. The darn things just refuse to fold over the edge of the wheel or platen like a cloth belt does. Put a little force on them and they rip when you try it. Slack belt work with these is also an adventure. They're so thin that they really cut deep when you get a bit careless and let the side of one touch skin.

Don't do slack belt work on the area between the idler and the knife maker attachment. Take the platen out and work between the two and five inch wheels. It's only three little screws and takes about a minute. Wooden sheaths and wood or micarta grips are really easy to shape and darn near finish with this trick. Kill the belt edges with a piece of crock stick so they won't dig in. Doesn't work on Square Wheel.

Slack belt finishing on contoured shapes often works a lot better when you split the normal two inch belt into three or four narrower bands. A half inch wide ribbon conforms to smaller, inside curves of finger grooves easily.

Always respect the edge of the belt. It can sink into a fingertip about a quarter inch before you know it. and boy, do those hurt. The rougher belts won't even stop at the bone. I've done my left index finger about five times now. Thankfully, the nerves are pretty well deadened and it isn't too painful.

If you have a problem keeping a flat surface, or hitting the groove on hollow grinding, it's usually related to the way you hold your blank while grinding. Try to lock your forearms into your hips, lock your wrists and produce the side to side motion by swaying your torso back and forth. This makes it much easier to repeat the same cut, over and over, but I'm not going to mention how it looks from the back. Always bring the blade to the belt with a very light hold, allowing it to settle on the existing grind before firming up the grip to make the cut. You have to find the "old cut" before you are able to make a correction. Lead with the cutting edge so you won't nick the grind line.

Always leave a bit of metal at the top portion of the blade grind where it meets the spine or centerline. You'll forever be adjusting the flair out, or the center line, so leaving a bit makes it a lot less noticeable when you have to correct things a few times. The solution to a dagger that has been a bit overdone in that area is to grind down the entire thickness of the back end of the blade. New knife makers often have blades that are only about half thickness at the area where the grind lines meet at the plunge cut or the grind reaches the spine.

Flat or hollow grinding, the cutting edge should be up while you're shaping the Vee part of the blade. Surprising how many new fellows mistakenly think they might snag the blade like this. The belt will not snag on the cutting edge, and grinding is a lot easier when you can see where you're going.

I cannot recommend home made belts for use on any machine. Commercial, glue bonded belts are not for cutting steel, get resin bond. Lap joint belts will rattle and thump enough to drive you crazy if finer than 60 grit, so get the butt or finger joint style for any grit finer than around 80.

I found my cutout belts wearing thin at one specific spot, time after time. It turned out that some dust or rubber wheel particles had welded themselves in a ring right around the contact wheel, and were raising that part of the belt a bit. Scraping the wheel surface with the unsharpened edge of a blade removed it and the problem was solved.

Flat grinding is pure hell on a belt. Many of the butt joint types will not stand up to the stress, and when one pops it sounds like a pistol going off. Makes you sort of gun-shy for awhile. The absolute toughest joint found to date in our shop has been on the 3-M Regal belt with a lap joint. These also seem to cut a significant amount better, taking off more steel than any other brand or type of zirconia belt we've tried, although the Hermes ceramic performs about as well. If most of your work is hollow grinding, you won't notice the difference nearly as much because hollow grinding needs the sharpest part of the belts' life.

Breaking belt joints may simply be a symptom of too much heat in grinding. We blew up a case of the best before discovering that silicon spray on the back of the belt would reduce friction and heat to the point where they no longer melted the Mylar protecting the fibers of the joint tape.

Hollow grinding is a lot easier on a belt than flat grinding against the flat platen, but it doesn't always increase the belt life. Use the Loveless technique and grind a 45 degree starting bevel along the edge with an old belt to make them last longer. The trick and many more are explained in detail in his book which should be in every serious knife makers' library. While belt life is better, it may not be possible to use the extra belt life during hollow grinding. Anything but a fresh, sharp belt for hollow grinding is asking for trouble. A dull belt catches and screws up the cutting edge when the belt rolls over it. ( The belt does not catch by itself. It snags when there's too much pressure used to make the belt cut, and you give the blade just a bit too much turn in at the top.)

You can get a lot more mileage out of a belt in hollow grinding if you leave the work rest in place and use it to steady the blade. Put the spine of the blade on the work rest and just turn the blade into the wheel. After a little practice, you can plunge cut two inch wide sections very evenly.

Hollow grinding can be extremely difficult for the new guy, especially in the area where you're shaping the tip. Resting the work on the work rest lends to cutting a straight line and free handing it leads to a lot of whoops'. If you clamp a short section of 3/4" or 1" diameter half-round stock on the work rest, it'll give you all of the needed support, but allow you to rock the blade as you move it back and forth. This makes it a heck of a lot easier to form the tip. See the sketch.

When using the work rest to support a blade that you're moving back and forth, grind the spine with scratches that run lengthwise, not across. If the marks are going across, they'll act just like a file and cause some rapid wear on the work rest.

The Burr King and other knife grinders are a fairly open unit, which means a lot of grit comes right around back at you. Wear safety glasses and a cap with a baseball style brim pulled well down to protect your eyes whenever you are grinding. You'll be amazed how soon the edge of that cap brim gets burnt up. (If you put belt guards and shields on, they'll rattle and get in the way). Slip a clean shop rag under the back of the baseball cap, covering the back of your neck and hair. Your wife will be pleased when the back of your favorite chair and your pillow don't turn that nasty gray anymore.

Never get your fingers or gloves in an area where they could get caught between the belt and a wheel. The wrist was not intended to rotate 90 degrees. That sudden trip around the wheel, and the pinch are enough to make one quit knife making and take up professional knitting. I don't want to even think how it would go if the work rest were in place.

Vibration can be very irritating. It's usually dust, packed up, off center inside the idler wheels' rim, or the contact wheels' rim. Run the machine and brush it out with a stiff paint brush or a push stick. Don't forget the left side. Compressed air gets it out too. If the vibration persists, check the drive belt for missing chunks or severe wear. The 960 Burr King uses a 25 inch drive belt, not a 24.

The first thing to check, should there seem to be a vibration, is the belt joint.

Compressed air is real handy for blowing wood or plastic out of a clogged grinding belt. Those rubber eraser cleaning sticks actually work for removing clogs of softer material, but aren't too good for getting metal flakes out.

When a new belt seems to dull while grinding carbon steel, save it for stainless. The carbon steel leaves little bits welded to the top of the belt grains, pretty much killing the cutting. Switch to stainless and use heavy pressure, breaking away the clogged parts of the grain. The belt usually has plenty of life left.

If the machine seems to bog down easier than it did when you started, it's usually the drive belt slipping on the pulleys. Smoke coming out of the holes in the frame castings' side is a good clue. Burr King never mentions how to tighten the drive belt, so here goes. Loosen the two adapter plate nuts. They're inside the main casting, one on each side of the motor drive pulley. Use a socket with an extension through the holes in the side of the casting. Take a pry bar, or bowie blank, set the tip into the center hole of the drive pulley, aiming the tip of the pry bar forward from the rear casting hole. Pull the other end of the bar forward, forcing the whole grinder head to the front and tighter against the belt. Holding the pry gadget, tighten the front nut firmly. Remove the pry gadget and tighten the rear nut. You should be able to move the belt about a quarter of an inch up and down, no more.

If your grinding belt runs off to the right every time you put heavy pressure on it, it's slipping on the drive wheel and needs more tension to keep it running right. This is more common with the Bader than Burr King.

When the machine won't hold the belt in track try putting a little more crown on the rubber wheels with a coarse file while they're running. This is a dangerous procedure, so be careful. Brand new wheels usually have a feather of extra rubber on the corners and it creates all sorts of tracking problems until removed. This is a bit risky if you're not very, very steady. A crown can be faked on the metal idler with a few layers of masking tape wound neatly around the center. Silicon spray will make tape come loose. Heavy duty flat grinding always stretches a belt, so some adjustment is going to be normal.

Always stand to the side when you start the machine after putting on a new or used belt. You never know if the wear, stretch or adjustment is way out of whack, which can make the belt do some pretty crazy things when you hit the switch. It's best to spin the belt by hand before hitting the switch. Also, spin the belt manually each time you change set-ups. Tracking might change quite a bit on different configurations. Lining the belt up perfectly centered on the wheels when you put it on doesn't accomplish a thing. The belt is going to run to the high spot of the tracking wheel, no matter where it starts from.

If you hear a tick, thump or any other odd sound while grinding, stop the machine and check the belt joint immediately. Grinding belts make lousy neckties. I've had one hit with force enough to shatter pens in my shirt pocket.

When replacing worn out contact wheels, check out what you'll be getting before laying out your hard earned cash. Factory replacement wheels from Burr King are fine! Do not get plastic wheels. Granted, they're tough and resist cutting very well, but they can't take the heat, particularly when you nick the side of one. We've also found some "will fit" type replacement wheels to be undersized and off balance - and not that much cheaper. Don't rush out for a replacement wheel when yours gets nicked. Most wheels will run with what appears to be a deep and ruinous cut. As long as there is no tendency to snag, there shouldn't be a problem.

Most grinding errors happen when you're trying to push a belt just a bit too far. Dull belts grab and snag far easier than one that's cutting. Try to keep your belts in stages, groups broken down by their relative dullness. The simplest rule is to work the broadest areas first, and proceed to jobs that are narrower and narrower until you are cutting out patterns from bar stock. ( When I say "grab", I mean that the blade will catch and be pulled down an inch or two, not jerked right out of your hands.)

Working close to the belt may be frightening, but is the steadiest and most reliable way to hold a blade. New knife makers will find it difficult to get close, but, with proper care, working close will make a better blade faster. I recommend a pair of vise grip pliers to hold the tang, and a push stick to force the blade to the belt. The hand that holds the push stick should rest firmly against the body at the hip point or stomach. Many of us serious professionals have spent a lot of time eating rich food to make that area larger and firmer. And to keep the rough parts away from the pink parts, I always wear gloves until I get to the final polishing.

The small wheel attachment can be a puzzle to set up the first time. Remove the back idler. Take the two inch wheel from the top of the flat grinding attachment and put it in where the idler was. Slide the small wheel yoke in where the two inch wheel was with the little forks for the small wheel set a hair ahead of the platen. You do not have to remove the platen. Put on a belt. Loosen the flat grinding arm lock screw and tip the arm forward until the belt is nearly tight. Lock the flat grinding arm again. Tension the belt and you are ready to start. Check the tracking. The really small wheels overheat immediately on the standard speed grinder and can't be run much longer than a minute.

Heavy blades will beat down the grain of a belt a lot faster than light ones. You'll be tempted to grind the heavy stuff first, but don't. Do the delicate ones first, then go on to the big lumps that break down the grain. The grit is supposed to fracture, giving you new, sharp grit as the belt wears down. The belt should give you about 10 to 20% more, once you learn to read its condition and adjust to that by grinding parts that suit the belt at that time.

I recently tried the 3 - M Regal brand belts. They give 200 to 300 per cent more metal removal than any of the zirconia belts that I have had the chance to work with. There are also Regal Lite and other variations, but they don't work quite as well. Hermes has a ceramic belt, similar to the Regal, in the works and it performs just about as well. 3 - M Apex belts seem superior in the middle range of finishing. Bargain belts usually aren't.

Never grind after a meal that includes broccoli, cabbage or Brussel sprouts. One burp inside the dust mask could have near fatal results.

Working with the cutting edge up while grinding may seem dangerous but it's not. You do have to be very careful not to drop a blade on top of a moving belt, because it really flies, but don't worry about snagging the cutting edge and having it take off on you.

For a point of reference, the belt, at around 5,000 feet per minute, is moving at 60 miles per hour. You certainly wouldn't want to rub your knuckles on the highway at 60, would you?

Another tricky item is that bottom wheel on the grinder, normally made with an aluminum core. Just touch the tip of a blade to that aluminum and it digs in. The wheel is going around like crazy, right? The blade goes flying, fortunately, it usually hits the floor.

Belt snapping is another danger. They normally hold together very well, but when one lets go, they pop with a tremendous bang, scaring the living heck out of you. On occasion, one only half breaks, and the flapping end will whip you about half a dozen times before you can pull away. Belts do not just decide to come apart all by themselves. They have a knife maker there to help them break. Most belt failures happen when the nut at the grinder is trying to fold the belt w a a a a y too far over the side of the platen or wheel. If you get a buzzing vibration or loud hum when grinding heavy, you're punishing the belt joint severely. Some blades have harmonic spots where the weight of the metal makes it hum, no matter how careful you are. We found that the irritating vibration can be reduced a lot by simply working lower down on the platen.

This humming can create another problem when you're cutting out patterns. The vibration can actually crystallize the cast aluminum work rest arm, making it brittle and likely to snap after repeated use under those conditions.

With platen, flat grinding, the sharp edge of the steel platen will very often catch the very corner of the belts' joint and force the joint to fail, especially with finishing belts. Try cutting the platen about an eighth of an inch narrower than the belt and rounding the edges slightly. ( You can't do that with a Square Wheel brand.) Also, a freshly surfaced platen with coarse new grinding lines on it will wear through the belt joint in very little time. Polish a resurfaced platen down to 220 grit to reduce friction.

Slack belt grinding offers the opportunity for a lot of damage to ones' anatomy. You're working close to the belt edges with unpredictable movements on an irregular surface. To make it worse, the belt wanders all over the wheel, working from side to side as you exert pressure on it. We recommend using a piece of sharpening stick to kill the very edge of any belt used for slack work. It'll help prevent the slight lap marks that are so irritating but WILL NOT protect your fingers at all. Never extend the fingers beyond the work piece, past the edge of the belt, when slack belt finishing.

Most belts will accept quite a roll-over at the edge when cutting deep "inside curves", but a few brands give up the ghost if the edge so much as bends. Some brands shed at the edges, getting narrower all the time, others wear thin at the center of the joint. The best idea is to test different brands to see which fit your needs best. I could mention a few of the stinkers, but they'd sue me if I did it in print. We all eventually adopt our own unique style of grinding and settle on a belt that works with that style. The best recommendation that I can offer for new hands, is to try to wear out the center of a belt before using up the edges. A lot of inexperienced grinders use the outer corner of the belt to "chip" away at steel bulk. It'll cut steel off fast that way, but wears out the belt in a very short time, and breakage is much more likely to occur. Hold the blade tang with a vise grip pliers for more control.

You might never think of this one. My shop is sort of tight on space, so there's not a lot of room to move around. A helpful apprentice once cleaned up the floor around the grinders to make the shop neater. I banged my elbow into the running belt four times in less than two weeks. It was still bleeding through my shirts at the Guild show, embarrassing. The apprentice had accidentally moved the grinder about two inches farther out from the wall, and I had kept on turning around in the same spot I'd always used.

If you smell electricity, turn the machine off immediately! What most of us smell and think of as electricity is ozone, and it is one major league, nasty thing to breath in, causing liver damage and a host of other medical problems. Inexpensive, brush type motors, like on a cutoff saw, are the worst offender, sparking like crazy when things get worn or out of adjustment.

Here's an odd one that caught me. Should the power go off, go around and turn everything in the shop off. That way, you won't have to come out and do it when the power comes back on at three am.

Another obvious, but often overlooked safety item with machinery is, you don't try to run something until you see if it rotates freely by hand. In other words, give it a test spin. If your hand won't turn it, the voltage certainly won't either. I use this with grinders and buffers, or even the cutoff saw, but won't trust the table saw for that sort of test. I'd rather burn up the table saw! Bandsaws may be spun whenever you change the blade, but I wouldn't try pulling the blade itself.

Never use a ventilated or open type motor in a knife shop. The air is full of abrasive dust that will wear out the electrical connectors and bearings in a very short time. The motor then self destructs, sometimes with fireworks. If you have to use an open motor, get one with a warranty. Then you'll get a free, new one when the darn thing wears itself to death on the grinding dust.

Most of the dust in the shop is iron. It collects on top of the electrical boxes. Some of it dribbles down in through the cracks. It is conductive, and eventually shorts the box out. Blow electrical boxes out regularly. If you want to make the process more exciting, don't turn the circuit off before starting to blow it out.

The dust that collects on top of a electrical box will sometimes dribble down across the front of it, making a lovely fireworks display when it shorts across the bare metal parts of the plug on the cord that's plugged in there. Personal experience taught me that it'll send a plug sailing right across the room with thirty amps of 220 behind it. It looked like an angry cobra. Kind of makes you shake your head for awhile after that happens. I put tape across the top of all the boxes in the shop, leaving it hang over like an awning to prevent the problem.

© Copyright 2005 Bob Engnath All rights reserved.

Bob Engnath on Grinders
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