Hand planes are critical for several steps in the violin making process. These include jointing the top (and often back) plates, smoothing the top and back plates where they will meet the ribs, and preparing the bridge, blocks, finger board and neck heel. Some use it to trim the rib height as well. One of the most challenging tasks though is the planning of the ribs.
General setup of a hand plane includes proper sharpening and lapping of the blade and lapping of the sole. However, this discussion will focus the angle the blade meets the wood (generally ‘pitch’ angle).
A small plane is more convenient for the fine work of preparing a rib surface. However, the out-of-the-box setup of blocks planes, particularly low angle planes, are not well suited to work on highly figured wood. An understanding of blade pitch can help avoid frustration when planning your ribs.
Hand plane pitch refers to the angle made by the cutting surface of the blade to the wood surface. To go further in this discussion, you need to understand that there are two basic configurations of planes, bevel-up and bevel-down
Bevel-down refers to a plane where the blade is installed with the flat side of the blade up and the side containing the bevel, created when grinding the cutting edge, is installed downward toward the bottom of the plane. This is common to most bench planes.
Bevel-up refers to a plane where the blade is installed with the flat side down, and the ground bevel facing up. This is typical of smaller planes; such as block planes.
Whether a plane is bevel-up and bevel-down impacts the angle that the cutting surface meets the wood surface. This angle affects the rate of cutting, and the ability of the tool to cut perpendicularly across the grain, such as when trimming end grain, a low angle is required to slice through the grain. In cabinetry, this application is most often the purpose of a block plane. To cut along the surface, parallel to the grain, a medium angle is used when the grain is straight. A lower angle here provides faster cutting. However, for highly figured wood a high angle is needed to prevent tear-out, this in turn slows the cutting speed by increasing the pressure required.
For bench planes the ‘frog’ sets angle at which the blade cutting surface meets the wood. There are some traditional terms that refer to various pitch angles, illustrated below.
Block Plane Blade Geometry
A low-angle block plane with a couple blades provides the most flexibility. Let’s look at three setup options for a typical low-angle block plane.
For cutting end grain, such as shaping corner blocks, trimming finger boards, or flattening the heel of the neck the standard configuration can be used. A 25 degree bevel blade provides the best result.
For preparing the surface of ribs, the back plate before hollowing, or the top of the neck or the back of the fingerboard, a higher angle bevel should be used, either a 38 or 50 degree.
Toothed blades are also available for working highly figured wood. These blades have higher angles, because they present less cutting surface they work quicker to remove large amounts of wood. They of course do not leave a smooth finish so they need to be followed up with a high angle.
Cheating Bevel-Down Pitch Angle
A bench plane bevel-down blade would seem limited to the angle of the frog for setting the cutting surface to wood angle, however, there is a cheat: back bevel. By placing a small bevel on the flat/lapped side of the blade, the effective pitch angle is made steeper.
In conclusion, for the violin maker working with complex figured grain, such as planing flamed ribs, there are a couple options:
- Option 1: A scraping plane with a toothed blade produces a relatively smooth surface. Finishing must then be done with a scraper or scraping plane with a normal blade. A plane with a high angle bevel could be used, but that would be somewhat redundant.
- Option 2: A plane with a high angle bevel can be used to prepare the finished surface. A scraper is optional given the high quality of the surface produced by the plane.
Note: removing large amounts of stock is best done with a toothed blade. The higher bevel angle reduces tear out while the toothed configuration improves cutting speed.