How to bend
A Board
How to Bend a Board - Kerf Cut
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oh hey what's up working hard or hardly
working
hardly working today we just did a
dining room of crown molding and we're
waiting for the caulking to dry before
we can paint it so we're going to give
that a couple of hours but I thought you
know what the heck let's go outside and
show you guys how to kerf a board if you
don't know what that is let's go outside
and check it out so here's our little
setup for kerfing a board what we use is
a sharpie speed square and this little
setup that you see right here so this is
a pretty simple process and I'll explain
to you
kerfing a board is for trim carpenters
basically what it is is we're going to
make a series of cuts all along the back
of this 1 by 6 MDF this is 3/4 inch
thick by 5 and a half and we're going to
make a series of cuts that are 3/4 of an
inch from one another and what that's
going to do is that's going to allow
this MDF to get a really good bin to it
so we can curve it around an arched wall
this is just an example today we're not
doing anything like this at this house
but we've got some time to kill so
here's how I do it what you want to do
is get your circular saw calibrated this
is a rigid and the fence on this from
this fence to the blade is an inch and a
half but that's too big for the kerf I
need it to be 3/4 so this little divot
right here where this goes in that's the
run of the blade that's exactly where
the blade cuts so you can follow those
lines but what I'm going to do is I'm
going to get on that with just an using
the 7 here you can use any number I just
don't like to use the end of the tape
measure
I feel that this is more accurate so
right on that seven and then I'll go
over three quarters and I'll make a line
right there it just needs to be three
quarters from that line you can see
right there
so what that's going to do that's going
to allow me to line up that sharpie line
with the next cut and that line doesn't
have to be pretty obviously you can see
it's not perfectly straight I just it's
just a little line so you can know where
to make the next cut so before I make
the first cut on this piece of MDF what
you got to do with your circus circular
saw is set the depth and I'll come
around here to show you how I do that
there's this little blade guard you want
to lift that up and you can see that's
going to cut straight through the piece
we don't want that we want to go about
half way through with that depth on that
blade so I'm just going to eyeball it
and call it about half way right there
you see how that looks from this side
and that looks pretty good actually
right there
so I'll lock the saw down I'll make sure
that that's locked in place now my saw
is calibrated and I'm ready to make the
first pass of the circular saw so here's
what I'm going to do when I get started
I'm going to take this speed square in
my left hand with the fence of the speed
square away from me that way I can grab
onto it and slide it out like an
adjustable fence and this circular saw
the fence on the left side of the
circular saw is going to ride against
that so what I'll do is I'll get that
sharpie line lined up with the edge of
the material and then I will make the
first pass
so with that first cut now it's just a
repetition of lining up the Sharpie line
with the previous cut and I'll do that
the whole way down
and I can already feel the flexing over
here but it won't be until I get the
full board curved that we'll be able to
actually bend it if I try to bend it
right now it would just snap right here
at the weakest link right here where
it's as a whole board this is the
weakest link so I just thought I'd
mention that but this side over here is
really flexible
and you can see this part that I already
did thats hanging off I don't want to
bounce it around too much but it's
really bendy right now alright so that's
it this is the kerf that we did and you
can see just how flexible it is and we
will break this board I'm going to push
it to its limits but before I break it
and push it to its limit if we wanted to
get some more Bend out of it what we
could do is we could set the depth of
these cuts a little bit deeper but you
don't want to go too deep because you
could end up breaking the board that
right there is a good amount to keep the
wood strong and together or in this case
the MDF so MDF if you ever worked with
it you know already that it's a it's
already flexible before you do this but
I've got a piece it's the same exact
size over here and I'll show you what it
looks like with the kerf verses without
the curve so here's without I'll set
this one down and I'll try to bend this
it bends alright and we're going to push
this to its limit but it bends pretty
good but it's going to break now watch
how much I can get this thing bit
pretty cool it bends a lot more but it's
always going to break at that weakest
link whatever it was the the weakest
link was right there at that cut maybe
it was a little bit skinnier than the
other ones but we've still got this
piece you can see how it keeps breaking
you can see how you could get that so it
keeps breaking you can see yeah
so yeah in all seriousness that was
pretty funny but in all seriousness this
is a really cool method to get around
curved walls and incurved architectural
drywall and it really works we've used
it before
now if the wall is too curved you're
going to need to go to the the rubber
you know the flexible millwork route
yeah it's a really cool method we use it
we've used it on baseboard before where
we take the same method and we just
score the back of the baseboard before
you get to the top so you don't see it
in that top profile and it works great
so anyways hope you learned something
from this video about kerfing it's a
really cool method and I will see you
all next time
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