I cut some coves on the table saw
while making a picture frame.
And I slightly improved the process while I was doing that.
So I thought I'd make a video of that.
Circular saw blades are really meant to cut like this,
just forward to cut the slot. But when cutting a cove,
you pass the wood across at an angle
so the teeth kind of sweep out like this,
and they cut this channel.
But you have to do it in
very shallow steps because only the tops of the teethes cut.
Another problem is the shape of the teeth is not ideal.
The teeth on a circular saw blade are designed to cut
a clean channel on the edges.And so the teeth have points
that point either this way or point
in the opposite direction to make
sure they cut a nice, clean edge.
And the middle of the cut is not really that important.
So they have alternating teeth that cut either this profile
or this other profile, and that leaves a cut
that is usually not quite as deep in the middle,
which is just fine for cutting through.
But if you're trying to cut a cove and the wood is
passing along like that,
you really only have the points on this side cutting this half
and it points on the other side, cutting the other half.
So effectively, the shape of the cutter,
becomes a point like this, which is the corner of a tooth
and then the next tooth cuts like so
and like so, and so on.
and that leaves, basically a very jagged edge on the wood.
So I realized, rather than having teeth that go like this,
and like this, if I had teeth
that just kind of went like this,
that would be much better because we wouldn't have the
sharp point doing all the cutting.
So, I ended up taking a saw blade
and I took every tooth that was like this
and ground the corner off it, like so.
So I used my table saw blade sharpening jig
to grind away the alternating points
just by holding it against the blade, like that.
I wasn't sure if this whole experiment would work
so I actually used a blade that was kind of dull to begin with,
and had a missing tooth, because I figured
nothing to lose with this one.
So, I just went one step further and actually rounded the
tops of the teeth and that should work even better.
If you don't have a fancy table saw blade sharpening gadget,
you just use a diamond disk on a dremmel tool
and that works surprisingly well.
So, here's my samples and at a glance,
they didn't look that much different. But, let's
put the light at a low angle
and zoom in a bit. So, this is a conventional method of
cutting coves and you can see, especially along here,
you can see there's all these little
ridges in there from the blade.
This is with the improved process.
This is just cutting the corners off the blade.
And you can see
this one is a fair bit smoother.
And with the rounded teeth,
is this one,
and it's not that much better.
I think if I had a more precise way of cutting these things,
it might work better. The other problem might be
just cutting at an angle like that,
might chip-out the wood a bit more.
I just repeated that same test with some nice maple,
which doesn't chip-out as easily.
So, this is with the rounded teeth
and this is with a conventional blade.
Quite a difference.
But, rounding the teeth actually didn't help that much.
And I think it's because I did everything free-hand
and I added more inconsistencies doing all that free-hand
work of rounding it, which is just
grounding off all the points.
The other improvement is to tilt the
blade into the cut a little bit
because the tops of the teeth cut much better.
So, as the wood passes across like that,
we're cutting more with the tops.
And if we have a wider blade, and in this case I just stacked
two blades on top of each other,
we get more cut area so we can cut more at once.
And I think an even bigger improvement would be if
we have one blade, which cuts like that, and
we take another blade
next to it, and then we ground
one into kind of a half-round like this
and the other one into a half-round like that,
so we'd have a cutter that makes this kind of profile.
I think that would work really smooth.
But, I don't actually have that many coves to cut
so I'm not gonna try that.