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Finest abrasives.
Microbevels front and back.
Use a jig.
Copyright (c) 2002-12, Brent Beach

Contents

Angles for Bench Planes

Most of the time you should be using a primary bevel angle of around 25 degrees, a first microbevel angle around 29 degrees. Use the extension calculator to build a suitable jig and suitable slips to get the appropriate microbevel angles.

I use the same final included angle is almost all my tests so that the results are comparable. It does not mean that you should use the same angle for all planing situations.

My standard angles, using a 2" jig and slips that are 0.08 and 0.13" thick:

Front Back
Primary 25
First microbevel 29 1.9
Second microbevel 30 3.1
Third microbevel 30.6 3.9

A general goal of sharpening is to use the smallest durable included angle. You can experiment with smaller angles than this, especially if you use more durable steels like M2 and D2. Elsewhere in the FAQ there is a discussion of steel composition and properties.

The primary bevel angle should be at least 4 degrees less than the first microbevel - otherwise the first microbevel gets too wide too soon, requiring more grinding. As the primary angle gets smaller, the primary bevel gets wider and takes longer to grind. The primary at 20 degrees is almost 25% wider than the primary at 25 degrees. The edge is also 25 percent thinner and hence less able to dissipate the heat generated during grinding. The longer you grind the more chance of burning the edge. As well, a smaller angle means a weaker tool. In my experience blade edge durability drops rapidly as the final included angle gets smaller.

A2 Steel

If you are using A2 blades you might find that the edges fail using these angles - you get little chips even when planing clear wood. You should increase the angles by a couple of degrees.

Tearout prone hardwoods

If you are planing hardwoods with a lot of figure and are finding that you are getting tearout you can reduce or eliminate tearout by using a larger back bevel. By using a final back bevel angle of 10 degrees, or even 15 degrees with certain woods, you can plane without tearout. You can do this by building a jig with a thicker back jaw. Again, work with the extension calculator to find a suitable jig size.

For example, if you build a jig with back jaw about 3/8" thick, then use it in the normal way, you will have a final 10 degree back bevel on the blade. A 1/2" back jaw will produce a final back bevel angle of 13.5 degrees. Notice that the total included angle is larger when you use a large back bevel -- 40 and 43.5 degrees in these two cases -- so the plane will be scraping more than a blade with a smaller total included angle. This will be a problem for tough or fibrous woods.

A blade prepared with a large back bevel could also have a much smaller front bevel angle, keeping the total included angle as small as possible.

Additional Discussions

There is another discussion of honing angles for plane irons on the Jig page.

Angles for Block Planes

There are two groups of block planes - those that bed the iron at 20 degrees and those that bed the iron at 12 degrees. Here I assume you are using the block plane for end grain. This discussion does not apply to block planes used for face grain, or bevel up bench planes.

When planing end grain the key consideration is the cutting angle - the angle between the upper face of the blade at the edge and the wood surface. Here lower cutting angle reduces effort and improves surface quality.

With a 12 degree block plane you must use almost no back bevel. To get a 30 degree included angle, you will need to put all of that on the front. The resulting cutting angle will be around 42 degrees. When honing a blade with no back bevel, you must hone the front bevel using your coarsest abrasive until you have removed all the back wear, then continue as usual with the next two front microbevels. The additional front honing with the coarse grit will widen the first microbevel quickly. You will have to grind the front bevel almost as often as you hone to reduce honing time on the first microbevel.

With a 20 degree block plane you can reduce the cutting angle, while retaining a large enough included angle, by relying on the back bevel. This, a final front microbevel angle of 25 degrees with a 5 degree back bevel gives you a cutting angle of 45 degrees. You could even duplicate the configuration of a 12 degree block plane by using an 8 degree back bevel and a final 22 degree front bevel, producing a final cutting angle of 42 degrees. To put an 8 degree final back bevel on the iron you need to use a jig with a larger back jaw. For example, you could build a jig with a 1.5" front jaw and a 7/32" back jaw, and use the standard slips.

In certain situations different angles might be appropriate. Lee Valley sells an edge-trimming block plane - a plane with a built in 90 degree angle fence. The plane is used mostly for squaring up wood - planing the edges - before glue up. The blade that comes with this plane has a 20 degree bevel. The blade works quite well on clear softwoods sharpened at this angle. The edge is immediately destroyed planing end grain white oak.

Angles for Chisels

Chisels are used in a much wider range of ways than plane irons. You should select a final included angle for your chisel to suit the task.

Paring chisels - pushed by hand and used to remove fine shavings - can have very small included angles. I have paring chisels with the final included angle of less than 20 degrees. Such a chisel cuts very well but will dull quickly in hard or abrasive wood.

Mortise chisels require much larger angles. Not only are the used with a mallet, they are also often levered against the shoulder to remove chips deep in a mortise. If you intend to work quickly with a heavy mallet in hard woods a final include angle of 35 degrees may be best.

How can I repair a badly pitted blade?

Sometimes you get an older plane with a blade that is badly pitted on the back. This usually happens where the cap iron meets the blade. Often only the last 1/8" of the blade has a problem.

The standard solution is to regrind the blade back past the pitting, then go through the usual steps of grinding the primary followed by honing.

You can often remove all the pitting in a minute or less if you have the hand grinding setup I use. The page on hand grinding includes a discussion of such a repair. The blade used in a grinding demonstration had a badly pitted back. The pits were removed in a few moments using a coarse Silicon Carbide stone with a standard back bevel setup.

How does skewing change the cutting angle?

You can change the effective cutting angle of a plane by skewing the blade edge to the direction of motion of the plane. This is typically done in one of two ways: using a skewed blade, or skewing the whole plane.

Skewed blades are found on a variety of specialty planes - both wooden and metal. Stanley made a number of metal dado and plough planes with skewed blades, as well as the #95 Edge-trimming block plane and the #140 Rabbet and Block plane.

Many manufacturers of wooden planes put skewed blades into Rabbet, Dado, and Fillister planes as well as bench planes.

The same effect can be achieved when it is possible to rotate the plane so that the side of the plane is not parallel to the direction of motion of the plane, or equivalently, the cutting edge is not perpendicular to the direction of motion of the plane.

This is not a large effect! Skewing the plane 15 (or 20 or 30) degrees reduces a nominal cutting angle of 45 degrees (bench plane with no back bevel) to an effective cutting angle of 43.1 (or 41.6 or 37.8) degrees.

  • The nominal cutting angle N is the angle of the upper surface of the blade at the edge, as measured from the plane sole.
  • The skew angle S is the angle between the blade edge and the direction of motion.
  • The effective cutting angle E is given by

    E = asin( sin(N) * cos(90 - S) )

What about ramped shooting boards?

Shooting board angled with plane A ramped shooting board, one in which the ramp on which the plane slides is angled with respect to the surface on which the board rests, gives the illusion of skew.

Here are two interesting examples of ramped shooting boards - follow the links to Fine Woodworking and HNT Gordon. Is is very interesting to me that the Australian board and the American boards slope in opposite directions. My board is like the American board.

The position and slope of the ramp is determined by the largest piece of wood you expect to shoot. If, for example, the largest piece is 3/4" thick and 5" along the face. Then 5" back from the fence the lower corner of the blade should be just below the lower corner of the wood. Measure the distance of the blade edge right corner to the plane right side. The ramp should be a little more than this down from the working surface when it first hits the work. At the fence, the top of the blade should be just above the top of the work. Measure the distance from the blade edge left corner to the plane right side. The ramp should be just a little less than this down from the top of the work at the fence.

If you are working 3/4 stock that is at most 5" wide, then the ramp would then drop 1 1/4" over the width of the 5" board, assuming a 2" blade. This means a 14 degree slope. This sketchup model shows a wooden plane with a 1 7/8" blade on a ramp designed to handle 5" wide, 3/4" thick stock. That is, if you were shooting such a board you would use the full width of the blade. Notice though that you do not make equal use of the edge - the outer bits still don't get a lot of use compared to the middle. Still, it is better than having all the wear in the middle of the blade.

Although the ramp is sloped (either way), this is not an example of skewing the plane to reduce the effective cutting angle. Since the plane slides on the ramp, and the blade edge is perpendicular to the ramp, there is no skewing effect.

You can do skewed shooting but you need to add a wedge to the plane body. For example, if you wanted to use a skew angle of 30 degrees, you would make a 30 degree wedge the length of your plane and adhere it to the right hand side of your plane (assuming the plane would run on its right side when shooting), sharp end to the back of the plane. If you slide the plane on the ramp, the blade edge is now skewed to the direction of motion by the wedge angle. You would have to drop the ramp by the thickness of the wedge at the blade. You could still angle the ramp to use more of the blade, again setting the ramp depth based on longest expected stock.

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