Shaping the Tool

Shaping is done with power equipment.  

You can do some things with a file or stone, but making blades from scratch requires power, especially when you are using hardened materials.  The Dremel, with all its attachments is a good start.  There are the abrasive wheels, stones, and sandpaper cylinders in various grits.  An 8" two wheel grinder will make the work easier, also.  But, even more so than with the Dremel, you must go slow and keep the blade cool.  I use a wet rag and keep water handy to cool between each short grind.  Feel the blade between your fingers after each grind and if it is too hot to hold, it's too hot.  Slow down and use shorter grinds.

I also use a belt sander, various sanding cylinders and disks mounted on old motors, and a slow speed sharpener made with an old dryer motor that had a double ended shaft.  As you see, I like old motors.  You can pick them up at flea markets and garage sales.  I am also not above asking a neighbor if I can scavenge the motor out of the washing machine or dryer he has put out on the curb for the trash.  A keen eye is worth real money when it comes to getting treasures out of trash.  I just have to be careful that my wife isn't looking. 

My original sharpener was made similar to one sold by John Burke for $300.  If you don't want to build your own, you can buy his.  He has a smaller RV version (only 2 wheels) available for about $250.  They run at about 300 rpm.  The motor has dual shafts and the buffing wheel is mounted directly on the motor shaft so that it runs at the full 1750 rpm.  The small 4" diameter grinding wheel on the left running at the 300 rpm speed produces less heat than larger faster wheels. It is slow enough to use with water so I used it as a wet grinder.  This allowed me to shape tools with even less chance of burning.  The 4" diameter produces a #5 sweep.  A 6" stone will produce a #3 sweep.  (For deeper sweeps, I use smaller sanding cylinders on a Dremel.)  The end wheels are easily changed so that other wheels and grits of sand paper can be used when needed.  
An old motor, a little scrap wood, and a sanding cylinder or disk makes a great tool.  I use several to finish shaping, smooth, and even sharpen blades and gouges.  These devices can be made with little cost, time or effort.  The sanding cylinders are the most expensive part and cost about $25 each.  The disk is available for under $10.  These three motors came from a dryer, an old furnace and a garage door opener.  I use the older motors.  New washing machines today have motors that are hard to re-use.  They have been cheapened and seldom have a full case.  They can be used, but require a little more work building an enclosure and mount.

What I didn't know was just how much more efficient it would be.  A simpler version of this belt sander was shown in the November-December 1992 Chip Chats.  But, I didn't realize the benefits until I was able to use one during a Gerald Sears Seminar.  After that, I had to have one.

After happily using the original sharpener for a year or two, I ran across a version of a belt sander specifically designed for sharpening knives.  I am a member of the Gateway Area Knife Club and am familiar with all the belt sanders that real knife makers use, so it shouldn't have been a surprise that the belt sander is faster and more efficient than the sandpaper wheels I previously used.

So, I proceeded to remove both the left and right wheels of my original sharpener.  The left wheel was modified and used to drive the belt.  The right wheel was removed and the shaft shortened to provide better access to the buffing wheel. The center two wheels were kept as-is to be used for knives.  Flat surfaces are better for knives while the sanding belt works for "V" tools, gouges and most other tools.  After a month of problem solving, I came up with the arrangement shown.  I use 80 (or less) grit for rough shaping new blades, and work my way up to 220 (or greater) for final sharpening.  A used 220 belt works fine for retouching a slightly dull tool and the final buffing finishes the process quickly and efficiently.  Buffing alone will keep a knife or gouge in tip top shape without using the sanding belt or wheel.

Blade Shapes:

Hollow

For a hollow grind, the edge is made by grinding two concave sides. If done right, this leaves the edge thinner than most blades.  It is very sharp and easy to push through the wood.  It produces the exceptionally good, clean slicing required for woodcarving. It is less suitable for rapid removal tasks.  The same thinness that gives the edge such great slicing performance also makes this blade more prone to chipping during high stress carving. This edge should be used for chores that emphasize clean cutting over impact and rough-out use.  To make this blade, the face must be ground on a wheel with the desired radius.  A 6" or 8" wheel usually provides enough curve for our purposes, but a 4" wheel will really give a concave surface.  It is harder to grind because you need a steady hand and/or a tool rest.  Making this blade out of a straight razor blade makes it easier, since they are already hollow ground.  See Make your First Knife section.

Convex

This grind has the sides of the blade arcing down in a convex curve to the edge. The edge on this blade is often very sharp because the convex curves run all the way to the edge without a secondary bevel. It is also a strong edge, because the thin edge thickens quickly enough to have plenty of metal behind it. It is useful for rough out chores.  It is also better for carving a small radius turn because it doesn't dig in as readily as the hollow ground blade and will turn back easier without splintering.  The main drawback of this blade is that it is more difficult to shape and to sharpen.  Also, it doesn't slice through the wood as easily as the other two grinds, even though it is correctly sharpened.  You can sharpen the edge in a normal manner, but then you will end up with just a regular flat edge.  Knife makers that have slack belt sanders can do it fairly easily with practice.  Using flat stones and wheels makes it more difficult.

Flat

The flat grind is a shape that combines most of the cutting ability of the hollow grind, with most of the strength of a convex grind. Flat bevels run all the way from the spine to the edge. This can leave the edge thin for high-performance. However, the edge thickens so it ends up stronger than a hollow ground blade. The combination of cutting ability and strength makes this a good all-around grind. This is also the grind that chip carvers use almost exclusively.  It is the easiest to grind on the flat stones and sanding disks.  It is also the easiest to maintain.

A Good Point

The point of any blade (as well as the corners of gouges) are the most difficult part of the tool to grind and keep sharpened.  The fragile point is easily broken or damaged.  Any knife will land on its point when dropped because the blade cuts through the air easier.  Well, that may be a little stretch, but it sure seems like it happens that way.  Anyway, the thin point or corner has less metal to conduct the heat away and is the first to get hot and the easiest to over heat.  When you see the point turn blue, its over.  You have to reshape the tool and get back to new metal.  Therefore, take your time, especially on power tools.  Use a minimum of pressure and short grinds.  Feel the tool after each grind.  If it is hot, give it time to cool.  Use water or a wet rag.  Shorten your grind time even more.  If possible, use your thumb to apply pressure to the blade.  You will know if it is getting too hot.  Dip the tool in water so that it is wet and stop the grind when the wetness disappears.  Practice - practice - practice.

Gouges

Shaping gouges out of spade bits or chisels is relatively easy.  This is done with any grinding medium that has the curve you want.  A 6" stone will produce a #3 sweep.  A 4" diameter stone will produce a #5 sweep.  For deeper sweeps, I use smaller sanding cylinders on a Dremel.  They come in many sizes and grits and you can pick the size  you need.  Start with the roughest grit and work your way down to the finest.  Complete the tool by hand with finer and finer sandpaper and finally by buffing with a cloth wheel.  Get all the sanding marks out for the best results.  Any sanding mark in the cutting area will make the tool drag.  If it is on the edge, it will leave marks on the cut surface.  A definite no-no.