QIt seems that every so often when I rip lumber, hard maple
especially, I get some
burning of the wood. Is there
something I can do to avoid this?
AIndeed, you are not alone; this is a common complaint. It results from the
saw blade rubbing within the cut,
generating heat. The heat, which is
not carried away very well by either
the wood or the saw blade, causes
some of the sugars to darken, or
when we get over around 400 F,
causes the wood to char slightly.
So, we need to address the
When a sawtooth cuts the
wood, the cells right at the cut
are slightly compressed, but as
soon as the tooth has gone by,
the cells spring back to their
original size. However, this
means that the slot that the first
tooth cut in the wood is now a bit
narrower than it was when the
first tooth cut it. Of course, the
saw teeth are the same width, so
even though this size difference
is so small that the teeth cannot
cut any more wood, the teeth
Another reason for the slot
closing after sawing is that there
is lengthwise (longitudinal) stress
in the wood. Such stress can be
in the tree (not very common
with North American species)
or because the stresses were not
adequately removed at the end of
drying. For example, if you rip an
8-inch-wide, 24-inch-long piece,
you should be able to put the
two pieces back together (minus
the sawdust) and find that they
fit perfectly with no visible gaps.
A gap indicates stress…natural,
growth stress or drying stress.
Of course, heating is worse
with a dull saw, so keep saws as
sharp as possible.
What would really help is if
the very front or top of the tooth
was just slightly wider than the
rest of the tooth. Indeed, this
is sometimes seen in saw teeth.
Some saws also accomplish this
by bending the teeth slightly one
side to the other so that the slot
cut by the teeth is wider than
the blade. Special note: As soon
as we ask the front of the tooth
to do all the work, then there is
no necessity to worry about the
sides of the teeth. In many saws
however, the sides are as sharp as
Another reason for rubbing,
especially when ripping with
a fence, is that the fence is not
perfectly aligned with the blade.
When you see the burn marks on
the wood, examine them closely
to see if it is the back of the saw
or front that is creating the heat.
We can reduce heating if
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