VERITAS Mk.II, Руководство пользователя

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35
General Sharpening Procedures
mortising and you have other chisels specifi cally for
paring, you should be able to put a 25° bevel angle on
all of them and be quite happy.
Paring Chisels
Paring chisels are usually the same basic design as bevel-
edge chisels, except that the blades tend to be a bit thinner
and longer. Square-edge paring chisels are less common
than bevel-edged ones but seem to be preferred by
shipwrights. Possibly this is because shipwrights tended
to use square-edge chisels in all of their other activities.
Cranked-neck paring chisels (no longer common) are for
use on large, fl at surfaces where an offset neck is needed
to prevent handle interference with the surface.
Since paring chisels are almost invariably used with
hand pressure alone and not with a mallet, they are not
subjected to the same forces as other chisels. In addition,
as their name implies, paring chisels are usually used
for very light cuts. As a result, they can be sharpened
at bevel angles of 20° or less. For very fi ne work, a
15° bevel angle is not unusual. Otherwise, the general
sharpening procedures described at the beginning of the
chapter apply.
Mortise and Firmer Chisels
Mortising is just about the toughest test of a chisel edge.
Cutting end grain subjects the chisel edge to nearly three
times the force of parallel-grain or cross-grain cutting. The
bevel angle on a mortise chisel has to be more obtuse than
on other types of chisels to withstand these forces. For
softwoods, mortise chisels should have a 30° bevel angle;
for hardwoods, a 35° bevel angle. These recommendations
are averages only. The steel in your particular mortise
chisels may let you get away with somewhat lower bevel
angles, or it may be relatively brittle and require somewhat
higher angles. Your guide is edge failure; start at a low bevel
angle and increase it only as much as required to prevent
the edge from folding or chipping.
"Firmer" is a term used to describe utility chisels of sturdy
build. They normally have square edges and since they
are frequently used for mortising, they are lumped in here
with the general recommendations for mortise chisels.
For speed of sharpening and best penetration,
I recommend a primary bevel of 25° and a secondary
bevel of 30° or 35°, as required, extending back to
about
1
/
8
in. of blade thickness (see the drawing on
the next page). It is apparent that a chisel of this shape
will penetrate more deeply than one that includes the
hatched area. The wedging action is reduced.
The edge has a strong secondary-bevel angle extending
well back; the only concern is the effect on rigidity. The
reason mortise chisels are as thick as they are is only
partly to provide the rigidity needed to counteract the
Paring chisels, shown in straight and cranked-neck designs, can be sharpened at relatively low bevel angles. Most people
associate the term ‘paring’ with small, light chisels, yet there used to be much larger and heavier (but still slim) styles used
in some trades – chisels like the shipwright’s socket paring chisel shown at top.
Mortise and firmer chisels require fairly steep bevel angles
in order to withstand the force of cutting end grain.