Bevel Up versus Bevel Down?
It
is often said that the wood cannot tell whether a plane is BU or BD.
That is true - it cannot tell the difference when both planes have
the same cutting/included angles, and when the blades are equally
sharp, and when they are both thick enough to avoid distortion.
However, there are pros and cons for both types of planes.
And here I must stress that the conditions of use as to be described
are as they apply in my shop. This will be the same for some and not
for others.
High cutting angles are preferred for interlocked
grain. For some, 55 degrees will do. For much of the woods I work at
least 60 degrees is needed, and yet some even higher angles - David
Charlesworth often refers to using 70 degrees. He does this in a BD
#5 1/2 with a common pitch frog (45 degrees) and a 25 degree
backbevel.
Achieving these high angles are easier using a BU
plane - simply alter the secondary bevel on bevel face. Unless it has
a high enough bed/frog, a BD plane will require two bevels - one on
each side of the blade.
Low cutting/included angles are also
the domain of the BU plane. Planing across the grain and end grain is
best served by a low cutting angle. Few BD planes can go below common
pitch. The 12 degree bed of the BU plane, along with a 25 degree
bevel, create an included angle of 37 degrees.
So, in effect,
the bottom line is that a BU plane has a wider range than a BD plane.
But that is only part of the story.
The advantage of
a BD plane for me is that the blade is easier to hone freehand. The
disadvantage of the BU plane for me is that the blade generally
requires a honing guide for the high secondary bevel angles –
and it is impossible to hone a 50 degree secondary micro bevel, plus
it is extraordinary work to create a camber on a thick blade with a
single, flat high bevel. Better to use a honing guide and a high
secondary bevel on a low primary bevel, especially if you want a
camber.
So I tend to reserve the BU planes for the extreme
angles. I do have BD planes with high bed angles, in fact I have an
equal number of BU and BD planes for planing difficult grain. I see
the advantage of BD planes in their ease of honing - create a hollow
grind and simply freehand on that. This
issue does not exist for those who use honing guides for all their
sharpening.
The aim in smoothing is to plane with the lowest angle that
produces tear out-free surfaces Lower angles tend to create smoother
finishes. However this is not always possible with interlocked grain.
In fact, in my experience, it is rarely achieved. It is safer to go
with a high cutting angle and so minimise the risk of tear out. And
if you really want to plane at a lower (e.g. common) angle, there is
no reason that a BU plane cannot be used as easily as a BD plane. In
fact, many would argue that the BU plane has greater potential and
ability at any angle in a comparison with a BD plane simply because
it does not require a double iron (the irons are generally thick
enough), and the blade is supported further than is the case of the
BD plane's blade. In practice I think that the thicker blades
minimise the latter advantage of the BU plane. I do think that it
remains a weakness for BD Stanley planes with thin and flexible
blades.
Regards from Perth
Derek
April 2011