Sharpening
Steve Nordhauser - 2/24/2009
There are many methods. They ALL work if done correctly. The only differences are time, money and the ease of use. One guy claims that although he uses water stones, he can put the same edge on with a concrete block and newspaper.
I’ve found that I have to think of my edges two different ways – two flat planes meeting at an edge (simple edges) and complex edges. Simple edges are woodworking irons, chisels, metal lathe tools, lawnmower blades. Complex shapes are carving tools, kitchen knives, wood lathe gouges.
For simple edges, the name of the game is repeatably bringing the metal to the sharpening surface at the same angle each time. This is what we do in grinding metal lathe tools – either through skill or a good table and miter gauge. For complex edges, the skill level is higher – a curve is followed or the tool is rotated.
Another thought – for manual methods, you usually have the cutting edge in the direction of travel like you are trying to slice off a shaving. For power methods, the cutting action is towards the edge. I sliced my first leather belt by not thinking this through.
To sharpen you go through a successive series of coarse to fine abrasives, each removing the scratches from the previous step. Each time a wire edge is left at the point where the two sides meet that must be removed without damaging the blade. The number of steps determines the fineness of the edge. The angle the edges meet at determines the tradeoff between fineness and sturdiness. 20 degree angles give a very sharp, fragile edge. 30 degree angles are much tougher but less sharp.
Some methods leave a flat surface (stones) and some leave a concave surface (wheels). The concave methods reduce the angle slightly and can add relief.
Micro-bevels – The idea is that you have a main bevel at one angle. Then you put a small coarser angle on the very edge so that less material to be removed. When you hone, you hone at the micro-bevel angle only. This leaves the very edge at a wider angle, making the very edge stronger.
I find that any method where I’m holding the blade at a fixed angle and holding it steady (simple edges) or passing it past something with a set angle (complex edges) reduces the chance of scratching up the side of the blade. This is why I do my pocket and kitchen knives on crock sticks or my belt sander. I always scratch them up with stones.
Don’t forget that a cutting edge is a meeting of two planes. Too many people sharpen the bevel of a single bevel edge and never touch the back. The back should be smooth and as refined as the cutting edge.
I’ve tried:
Manual methods
Arkansas stones – I still like them for a quick hone on metal lathe tools but they take a lot of skill.
Water stones – Japanese craftsman were meticulous – I’ve never had a better edge. It can take hours to properly sharpen. they are expensive, and must be maintained.
Abrasive paper glued to plate glass – the glass gives a flat surface. Of the manual methods, I like this one best for cost. It is easy to have a large variety of grits, it stays flat, and is cheap.
Diamond stones – Nice for carbide but I’m too cheap to buy expensive ones. I use the cheap ones for a quick touchup.
Ceramic rods (Crock sticks) – Excellent for general purpose knife sharpening – minimum skill on complex edges because the wood holder can set the angle.
Leather strop – Fine for a quick touchup to a razor edge. The leather should be glued to a hard backing.
Power Methods
Let’s face it, power can make things go faster – in a good way or bad way.
Grinding wheel – the tool we all love and hate. I need a better table on mine since I always get facets instead of a flat face. Aluminum oxide for steels except for carbide – for that use silicon carbide, but we all knew that. In general I just use it for shaping metal, not sharpening.
Buffing wheels – some people use hard felt wheels for sharpening. The only time I’ve done that is in my dremel tool to do very small edges.
MDF or cardboard disks – this is an odd one I saw at a woodworking show and tried for simple edges. I like it. You make a disk of stacked MDF, rough side out on an arbor and true it up. It can’t have any flex in it. Mount it so that it is parallel to the ground (drill in a vise works well). Charge it with a compound and it become easy to hold the tool at a repeatable angle. Since the wheels are cheap (make a bunch at once) it is easy to have one per grit.
Belt sander – for complex edges, this is my favorite. I have some fine grit belts for my 1x42 and a leather belt for stropping. I’ve always liked a firm backing to the area where I’m sharpening but I just watched a video where the guy had a knife ready to shave with using just a tensioned belt. My leather belt is branded Surgi-Sharp but I’m sure there are others.
Fancy systems – you can buy systems with belts and wheels, wet or dry, variable speed, battery operated, all kinds of guides. Many carving clubs own one for the club. The real advantage is in the guides for complex shapes since these require repeatability.
Sharpening belts – Aluminum Oxide, Silicon Carbide and leather:
http://www.leevalley.com/wood/page.aspx?c=2&cat=1,43072&p=48040
Leather wheels and belts:
http://www.thewoodcraftshop.com/store/c/602-A-Power-ful-Way-to-Sharp-Tools-.html
Trizact belts:
http://www.chippingaway.com/WoodCarving/SharpeningTools/UltimatePowerSharpener.htm
Youtube – there are lots of videos on sharpening and systems.
There are many methods. They ALL work if done correctly. The only differences are time, money and the ease of use. One guy claims that although he uses water stones, he can put the same edge on with a concrete block and newspaper.
I’ve found that I have to think of my edges two different ways – two flat planes meeting at an edge (simple edges) and complex edges. Simple edges are woodworking irons, chisels, metal lathe tools, lawnmower blades. Complex shapes are carving tools, kitchen knives, wood lathe gouges.
For simple edges, the name of the game is repeatably bringing the metal to the sharpening surface at the same angle each time. This is what we do in grinding metal lathe tools – either through skill or a good table and miter gauge. For complex edges, the skill level is higher – a curve is followed or the tool is rotated.
Another thought – for manual methods, you usually have the cutting edge in the direction of travel like you are trying to slice off a shaving. For power methods, the cutting action is towards the edge. I sliced my first leather belt by not thinking this through.
To sharpen you go through a successive series of coarse to fine abrasives, each removing the scratches from the previous step. Each time a wire edge is left at the point where the two sides meet that must be removed without damaging the blade. The number of steps determines the fineness of the edge. The angle the edges meet at determines the tradeoff between fineness and sturdiness. 20 degree angles give a very sharp, fragile edge. 30 degree angles are much tougher but less sharp.
Some methods leave a flat surface (stones) and some leave a concave surface (wheels). The concave methods reduce the angle slightly and can add relief.
Micro-bevels – The idea is that you have a main bevel at one angle. Then you put a small coarser angle on the very edge so that less material to be removed. When you hone, you hone at the micro-bevel angle only. This leaves the very edge at a wider angle, making the very edge stronger.
I find that any method where I’m holding the blade at a fixed angle and holding it steady (simple edges) or passing it past something with a set angle (complex edges) reduces the chance of scratching up the side of the blade. This is why I do my pocket and kitchen knives on crock sticks or my belt sander. I always scratch them up with stones.
Don’t forget that a cutting edge is a meeting of two planes. Too many people sharpen the bevel of a single bevel edge and never touch the back. The back should be smooth and as refined as the cutting edge.
I’ve tried:
Manual methods
Arkansas stones – I still like them for a quick hone on metal lathe tools but they take a lot of skill.
Water stones – Japanese craftsman were meticulous – I’ve never had a better edge. It can take hours to properly sharpen. they are expensive, and must be maintained.
Abrasive paper glued to plate glass – the glass gives a flat surface. Of the manual methods, I like this one best for cost. It is easy to have a large variety of grits, it stays flat, and is cheap.
Diamond stones – Nice for carbide but I’m too cheap to buy expensive ones. I use the cheap ones for a quick touchup.
Ceramic rods (Crock sticks) – Excellent for general purpose knife sharpening – minimum skill on complex edges because the wood holder can set the angle.
Leather strop – Fine for a quick touchup to a razor edge. The leather should be glued to a hard backing.
Power Methods
Let’s face it, power can make things go faster – in a good way or bad way.
Grinding wheel – the tool we all love and hate. I need a better table on mine since I always get facets instead of a flat face. Aluminum oxide for steels except for carbide – for that use silicon carbide, but we all knew that. In general I just use it for shaping metal, not sharpening.
Buffing wheels – some people use hard felt wheels for sharpening. The only time I’ve done that is in my dremel tool to do very small edges.
MDF or cardboard disks – this is an odd one I saw at a woodworking show and tried for simple edges. I like it. You make a disk of stacked MDF, rough side out on an arbor and true it up. It can’t have any flex in it. Mount it so that it is parallel to the ground (drill in a vise works well). Charge it with a compound and it become easy to hold the tool at a repeatable angle. Since the wheels are cheap (make a bunch at once) it is easy to have one per grit.
Belt sander – for complex edges, this is my favorite. I have some fine grit belts for my 1x42 and a leather belt for stropping. I’ve always liked a firm backing to the area where I’m sharpening but I just watched a video where the guy had a knife ready to shave with using just a tensioned belt. My leather belt is branded Surgi-Sharp but I’m sure there are others.
Fancy systems – you can buy systems with belts and wheels, wet or dry, variable speed, battery operated, all kinds of guides. Many carving clubs own one for the club. The real advantage is in the guides for complex shapes since these require repeatability.
Sharpening belts – Aluminum Oxide, Silicon Carbide and leather:
http://www.leevalley.com/wood/page.aspx?c=2&cat=1,43072&p=48040
Leather wheels and belts:
http://www.thewoodcraftshop.com/store/c/602-A-Power-ful-Way-to-Sharp-Tools-.html
Trizact belts:
http://www.chippingaway.com/WoodCarving/SharpeningTools/UltimatePowerSharpener.htm
Youtube – there are lots of videos on sharpening and systems.