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When sharpening any instrument, there are two important aspects. You want the edge to be as keen as possible and you also want it to be the ideal shape.

The sharpening of any tool takes generally two steps: Shaping and/or nick removal and Honing.

Terminology

See Fig. 1 for the basic bevel up tool geometry. Bevel up tools include chisels, gouges and block planes. "a" - Primary bevel angle, "b" - Cutting angle, "c" - Secondary bevel /micro bevel/, "d" - Back bevel.

See Fig. 2 for the basic bevel down tool geometry. Bevel down tools include smoothing and jointer planes. "a" - Bevel angle, "b" - Cutting angle.

1. Initial shaping or nick removal

In this step you decide the angle of the bevel. You also remove any nicks and irregularities making the shape of the tip perfect.

Shaping equipment you need

If you want the bare bones setup, get a bench dual water stone 1000/4000. It should measure at least 20 x 6 cm. Or even cheaper is a 600 grit sandpaper mounted on a block of wood.

If you want to go electric, for large mass removals, wet grinders are the best. There is no need to fear for overheating, but they are rather slow. Sides of the wheel can be used for flat surfaces. Cheap ones use vitrified stones which are less efficient but degrade more slowly.

When you use your normal dry grinder, overheating is a great risk. When that happens, the carbon in the steel combines with oxygen leaving you with just soft iron, plus you anneal the tip making it soft. The whole length where this occurs should always be removed. Also, quenching tips in water during dry grinding leads to tearing. The tip should be in contact with the coolant at all times, so don't use dry grinders unless you really know what you're doing.

If you must use a cheap dry grinder, at least change the wheel for something like Norton 38A80 and buy a separate tool rest. If glazing occurs, which can happen when you grind brass or with cheap grinders a diamond wheel dresser should be used to restore the wheel. It can also be used to remove any humps on the wheel.

Belt sanders can on many occasions be used instead of bench grinders.

Shaping

The shape and the bevel depend on the metal used but also on the use of the instrument.

Japanese instruments are usually harder 62RC allowing for a keener edge, so a bevel of higher 45° angle is needed to prevent breaking. With western blades which are a bit softer, and less prone to chipping, the bevel angle can be less, say 25°.

Cutting the denser sorts of wood requires blunter bevel angles, whereas softer woods allow for more sharply beveled tips. Ideally, the sharpest bevel should be employed which makes the tip still strong enough to withstand the pressure of the wood.

2. Honing

During honing you make the bevels smooth as a mirror. Then you create the micro bevel, making the tip as sharp as possible.

Honing equipment you need

The cheapest tools would be strops, leather or even better wooden. Cut a groove in a softwood, maybe basswood, apply chromium oxide compound and you have a perfectly shaped strop for honing. The same for the inner side. In seconds, you can make a wooden strop that fits perfectly the shape of your gouge.

For chisels and plane irons, if you can, buy a honing guide. It will help you make the bevels accurate and lead to consistent micro bevels.

An electrified alternative is the use of shaped felt wheels, which are ideal for honing the inside of gouges. They are a great substitute for the fine bench stones. The to of the wheel should rotate away from you. Belt sanders are great for honing with leather belts.

Micro bevels

Micro bevels save time, tools and energy. The finest possible edge in the shortest time. If you need fine angular control, use a honing guide. Only takes half a dozen strokes.

Sharpening tools specifics

Chisels
  1. If new, remove the lacquer.
  2. Lap the face so that the edge is not jagged. Make sure the stone is flat.
  3. Fix the nicked chisels on your bench stone or wet grinder.
  4. Hone.

A chisel should always be at the lowest bevel angle consistent with edge retention. Bevel angle should be higher for narrower chisels, say 30°, to prevent chipping.

Japanese chisels are usually made of hard steel face combined with an iron back which add toughness and flexibility to the chisel. The chisels are usually very hard 62-RC and therefore quite brittle. They are usually sharpened at higher bevel angles. Ideal for softwoods. Most of them are hollow on their face with just a couple of mm of a platform adjacent to the tip, to ease sharpening.

Planes

With a new plane you will probably need to lap the sole. It is usually hollow. You don't need to flatten the whole sole, but at the beginning, right before the mouth and at the end the sole must touch. Use 90 grit on a sheet of glass, iron plate or stone.

True the bed. Put some paint on the iron, insert in position, remove and see there it imprints. Carbon paper.

Dress the lever cap so that it is in perfect contact with the chip-breaker.

True the chip-breaker. At an angle that makes the point of contact at the very end. Have it set as close to the keen edge as possible, maybe 1mm, because the closer it is the smaller will the broken particles be resulting in smoother surface.

Sharpening the iron:
  1. If new, remove the lacquer.
  2. Lap the face so that the edge is not jagged. Make sure the stone is flat.
  3. Fix the nicked chisels on your bench stone or wet grinder.
  4. Bevel down bench planes Stanley no 7, have the usual grind angle of 30-35.

    Block planes such as the Stanley low angle 60 1/2 plane can be ground to 20° bevel and 5° back bevel to reinforce the tip. Make sure the iron sits in the bed perfectly.
  5. Hone.

Knives

For your knives a bench water stone, double 1000/4000 is alright. The bevels can range between 10°-30° depending on the steel and application. If you are concerned about the consistency of your bevels, you can use a spine clamp from you local stationery store. Put the clamp on the back of your knife to serve as an angular guide.

Honing can be done the cheapest on a leather strap glued do a wooden block, dressed with chromium oxide.

Gouges
  1. Bevel angle of 15 for soft woods and 25° for hard woods, 30°-35° with a mallet. All around 25°. In order to achieve the lowest bevel angle possible and the lowest gouge angle for the easiest cut, make the outside bevel 15° and the inside 10°. The inside bevel reinforces the tip and at the same time lowers the gouge angle required for a cut to 15°. This low attack angle requires less pressure on the gouge and makes your cuts more precise.
  2. You may also decide to change the shape of the tip's end. Square end is good for most purposes, fingernail end may be better for the scroll.
  3. To hone the gouges, either use a leather belt charged with chromium oxide on an electric belt sander. If you prefer manual, go with the wooden strop charged with chromium oxide.

    For the inside flute, a shaped felt wheel charged with chromium oxide is good. again going manual, cut the edge of a scrap wood which reflects the shape of the inside of the gouge perfectly. Dress with chromium oxide.

Scrapers

A well sharpened scraper should make clean shavings, not dust. In hardness RCs of up to 52 are now available. To create the edge, you need to burnish the scraper. Use a round burnisher or >RC60. Don't use the backs of you chisels, they most likely are not hard enough. Don't use screwdrivers as the chromium/nickel coating is thin.
  1. Joint the scraper first to give it a smooth edge at 90° to the sides. A jointing jig can be used with square scrapers.
  2. You can stone the surface, at the side of the bench stone. 1000x
  3. Put some nose grease on the burnisher.
  4. Clamp the scraper in the vice, and make a couple of strokes parallel to the scrapers edge with the burnisher slightly tilted as in fig. Hold it by the handle with one hand and by the tip with the other. Move the burnisher in a little to avoid using just one spot on it. In softer scrapers this will result in a small hook on both sides. With greater angles the scraper will have to be tilted more to the ground to bite. Use as few passes as possible. Try the scraper on the wood you intend to use it for.
  5. If you need more hook, run the burnisher at a slight 2°-10° angle to the edge. Do that a couple of times. Check again.

To "pick up" the hook after it has become dull, reburnish again with a few strokes. If that doesn't help any more remove the hook with the jointing jig, stone and burnish again.

Scraper plane

The scraper plane can be used when thicknessing the ribs. A 45° bevel is usually used. On top of that, you can create a hook at the end with your burnisher angled at 15°.

Stone truing

After a while every stone will loose its flatness. This may not be a big deal with gouges, but when sharpening chisels or plane irons, the stone must be reasonably flat. To true your stone, you can sue a coarse diamond bench stone, silicon/carbide paper on glass or even coarser stones, which can true your finer one.

Wood cutting tips

When parallel grain cutting, always cut with the grain, that is when the grain is rising up away from you.

If cutting end grain, always consider the skew cut. It is less demanding of the edge and lowers the bevel angle further.

When planing keep the mouth just wide enough for the shaving. This also results in smaller particles, smoother surface. Take thin shavings, they also allow for tighter mouth. Skew the plane wherever applicable. This applies especially if you have to cut against the grain.

Use a low angle plane, when cutting end grain.

For the cleanest cut with gouges, roll-cut.

Category: Tools and materials
Comment by 173.66.228.23
2014-12-08 01:32:15
In relation to sharpening scrapers, many violin makers would grind the scraper to a 45 degree angle not 90 degree, then turn the hook. A key point is not to press too hard when turning the edge, as you can spoil the edge - only light pressure is needed.
Comment by 173.66.228.23
2014-12-08 01:35:44
You need to give better advice on knife sharpening. It is not possible to produce a good violin without a really sharp knife, for example when cutting f holes, and the information here is too brief. It should include a test for whether the knife is really sharp, such as dragging it along your finger nail. The WorkSharp system for sharpening edge tools (both the flat disk system and the belt system) is really quick and easy to use.