Find the angle the edge actually meets the wood. Bevel-up planes add the honed bevel to the bed; bevel-down planes add a back bevel to the frog. Skewing the plane lowers the angle again.
Use this when you are choosing a honing angle for a bevel-up smoother or block plane, adding a back bevel to a bench plane for figured stock, or wondering how much a skewed stroke changes things on end grain.
You need numbers you can read off the plane and the blade: the bed (or frog) angle listed for the plane, the bevel you hone, and, for bevel-down planes, the primary bevel so the page can check clearance. Skew is the angle between the blade edge and a line square to your direction of travel.
The answer is geometry only. Chipbreaker setting, mouth opening, sharpness, and the wood itself still decide whether you get tear-out.
A bevel-up blade lies bevel side up on a low bed, so the flat back faces the work at the bed angle and the honed bevel sits on top of it. The angle between the work surface and the top face of the edge is the bed plus the bevel. Change the honing angle and you change the cutting angle; the clearance under the blade stays equal to the bed.
A bevel-down blade lies flat side up on the frog, so the frog angle is the cutting angle unless you hone a small back bevel on the flat side, which adds directly. Clearance is what is left between the frog and the primary bevel underneath. Skewing either plane shortens the effective rake in the direction of travel: the tangent of the angle shrinks by the cosine of the skew.
Bevel-up: cutting = bed + honed bevel; clearance = bed
Bevel-down: cutting = frog + back bevel; clearance = frog − primary bevel
Skewed: effective = atan( tan(cutting) × cos(skew) )
Each row below starts from the default inputs and changes only the columns shown. Recompute any row by hand with the formula above.
| Type | Bed / frog | Bevel | Skew | Cutting | Effective | Clearance |
|---|---|---|---|---|---|---|
| Bevel-up | 12 | 25 | 0 | 37.0° | 37.0° | 12.0° |
| Bevel-up | 12 | 38 | 0 | 50.0° | 50.0° | 12.0° |
| Bevel-up | 12 | 50 | 0 | 62.0° | 62.0° | 12.0° |
| Bevel-up | 12 | 25 | 45 | 37.0° | 28.1° | 12.0° |
| Bevel-down | 45 | 0 | 0 | 45.0° | 45.0° | 20.0° |
| Bevel-down | 45 | 10 | 0 | 55.0° | 55.0° | 20.0° |
| Bevel-down | 50 | 0 | 30 | 50.0° | 45.9° | 25.0° |
With the calculator defaults (Plane type = Bevel-up; Bed or frog angle (°) = 12; Honed bevel or back bevel (°) = 25; Skew angle (°) = 0), the arithmetic runs like this:
Bevel-up: cutting angle = bed + bevel = 12° + 25° = 37.00°
Clearance = bed angle = 12.00°
Result: 37.00° effective. Cutting angle 37.00°, clearance 12.00°. Low angle: easy pushing and good on end grain, more prone to tear-out on reversing grain.
Now change Honed bevel or back bevel (°) to 38 and leave everything else alone:
Bevel-up: cutting angle = bed + bevel = 12° + 38° = 50.00°
Clearance = bed angle = 12.00°
Result: 50.00° effective. Cutting angle 50.00°, clearance 12.00°. Raised pitch: helps on mildly figured or interlocked grain.
Re-honing the same bevel-up blade from 25° to 38° raises the cutting angle by the same 13°, from 37° to 50°, without touching the plane. That is the main reason bevel-up planes are popular: one body, several pitches, chosen at the stone.
Keep a second blade for a bevel-up plane honed at a high angle and swap it in when a board starts to tear. Raising the bevel from 25° to 38° on a 12° bed takes you from 37° to 50°, the same pitch as a 50° bench-plane frog. Going higher makes end grain and soft woods harder work, so keep the low blade for those.
On a bevel-down plane a back bevel of 5–15° is a quick way to raise the pitch without buying a new frog. It is honed on the flat side, so it is easy to add and annoying to remove — the flat back has to be lapped back past it. Try it on a spare iron first.
Skew is free pitch reduction. A 37° bevel-up setting pushed at 45° skew cuts like a 28° plane, which is why skewing helps on end grain and on shooting boards. It also widens the effective cut, so take a lighter shaving.
Units: Degrees throughout. Bed and frog angles come from the maker’s spec or a protractor on the bed.
Where the model stops: It is edge geometry only. Chipbreaker setting, mouth width, sole flatness, and edge sharpness are not modeled, and they often matter more than a few degrees of pitch.
Not a substitute: Follow the plane maker’s guidance on blade angles and on keeping enough clearance under the bevel.
Bevel-down bench planes are commonly 45° (often called common pitch), with 50°, 55°, and 60° frogs sold for difficult grain. Bevel-up planes are usually bedded at about 12°, and standard-angle block planes at about 20°. Check the spec for your plane — this page uses whatever you enter.
The underside of the edge must clear the wood just behind the cut. On a bevel-down plane that gap is the frog angle minus the primary bevel; if the primary bevel is as steep as the frog, the heel of the bevel rubs and the plane skates instead of cutting.
Yes — on a bevel-up blade the angle at the very edge is what touches the wood, so enter the micro-bevel angle, not the primary grind.
At large skews, yes. Using the formula, a 45° cutting angle pushed at 30° skew is about 40.9°, and at 45° skew about 35.3°. Small skews of 10–15° change it by less than two degrees.
For a spokeshave, yes, with its bed angle. A card scraper is held near 90° and works by a burr, so the plane model does not describe it.