125
Factors that influence the result
To get a 100 % straight edge when sharpening wide tools
such as a plane iron, you need to pay attention to a couple
of factors that influence the result. The grinding jig gives
the tool a constant edge angle towards the stone but the
shape achieved depends on how much
pressure
you apply
on the right or left side. Also the
time
you spend sharpening
on each side influences the shape.
If you press equally on both sides and move the tool evenly across the stone, you will get
a concave and not a straight edge. This is because the middle part is exposed to a longer
sharpening time than the sides. Compensate for this effect by spending more time sharpen‑
ing on the sides.
Camber Shape
Most types of plane irons should have a slight convex
shape or a camber. The degree of camber depends on
type of plane and should be approximately the same as
the thickness of the shavings. The camber (c) varies from
0.8 mm (
1/32
") for a jack plane down to 0.05 mm (0.002") for
a smooth plane.
The camber is achieved by pressing harder on the sides. A
longer protrusion of the blade in the jig will facilitate this effect, as most plane irons are a bit
flexible. On a thick, stiff tool you create the camber shape by spending more time sharpen‑
ing on the sides.
SE-77 Adjustment screws
For tools with a larger convexity you can use the adjustments screws, see below. If you need
additional convexity, sharpen free hand with the Tool Rest SVD‑110.
Loosen equally on the adjust-
ment knobs A and B. The side
then gets a pendulum motion.
The more you loosen the knobs,
the greater pendulum motion
you get, which increases the
convexity.
Center the tool under the jig’s center line, marked with a line.
Ensure that the tool is mounted perpendicularly by drawing a
line along the Universal Support (page 124).