VERITAS Mk.II, Руководство пользователя

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36
Veritas
®
Mk.II Power Sharpening System
force. As the tip is defl ected by the reactive force of the
wood, a beefy blade is needed to keep the chisel from
bowing and vibrating. But most mortise chisels are of
deeper cross section than needed for rigidity. The extra
depth is for alignment of the tool in the mortise. The
minor modifi cation of relieving the bevel angle detracts
very little from overall blade rigidity; it is usually not
noticeable in use.
If you are constantly working softwoods like clear pine,
the extension of the secondary bevel can be reduced
from
1
/
8
in. to as little as
1
/
16
in. of blade thickness. In
fact, with clear pine you can also reduce the tip angle to
less than 30° with most chisels.
Skew Chisels
Skew chisels are actually a
variant form of paring chisels,
though they are usually square-
edged, not bevel-edged. They
are most effective in end-grain
cuts and in paring the cheeks of
tenons. Wooden-plane makers
prized these chisels for working
the beds of planes, since the
square-sided skew would let
them work next to the cheek
without undercutting it, while
at the same time avoiding the
choppiness that could result
from using a square-edged
chisel on a plane bed. A skew
chisel will not suddenly dig in,
the way a square-end chisel
will. For similar reasons skew
chisels are ideal for paring
the cheeks and shoulders of
tenons.
Skew chisels are usually
sharpened with a bevel angle
of 20° or less. Depending
upon the equipment you have
available, it can be a tricky
process. Side-clamp honing
guides are of no use with
skew chisels, so you must either sharpen them freehand
or use a top-clamp honing guide such as the General
or Veritas guide. With either guide it is important that
the cutting edge be exactly parallel to the transverse
axis of the guide. This is not as easy to achieve as
you might think. It is simple with square-edge chisels
because you can set the bevel angle fi rst and then fi ne-
tune the squareness afterward. With a skew chisel you
have far more opportunity to go wrong. And this is one
case where you do not want to solve the problem with
applied geometry.
If you are using the Veritas honing guide and angle jig,
you will fi nd that the best way to set the honing guide
on a skew is to have it on the blade loosely as you set the
blade in the angle jig and then just release the honing
guide. It will slide down the blade and automatically
align itself correctly.
If you are using the General guide, concentrate on
getting the cutting edge of the skew chisel exactly
parallel to the front edge of the honing guide (90° to the
path of travel) and then adjust the tilt angle as required.
Corner Chisels
A corner chisel is used to clean the corners in mortises or
hinge gains. Large ones, usually 1 in. on a side, were very
popular with wheelwrights, who called them "bruzzes."
These are truly the chisels from hell when it comes to
sharpening. I used to think that sharpening a V-tool used
in carving was diffi cult, but it is child’s play compared
to doing a fi rst-class job on a corner chisel.
The fi rst thing you have to realize with the corner chisel is
that it has two faces, not one. Both have to be lapped until
decently fl at and then polished. Turning your attention to
the inside bevels of the chisel you will normally fi nd one
of two things. If it is a new chisel, the manufacturer will
probably not have risked sharpening it well and you will
fi nd a square edge, but one that is very blunt. If it is a
used corner chisel, the edge is likely to be fairly keen but
Skew chisels, available in
left- and right-hand pairs, are
specifically adapted to cutting
end grain.
Corner chisels, shown here in 1-in. and
3
/
8
-in. sizes, are used
to clean the corners in mortises. (Photo by Susan Kahn)
Bevel Angles for Mortise Chisels
Primary bevel (25°)
Secondary
bevel (35°)
1
/
8
in.