So I've got here a dovetail joint
that I cut out on my bandsaw
when I made the video about how to make
dovetail bandsaw joints.
And, since I have no use for it,
I thought I might as well test this joint.
And I'm gonna test it against this box joint which
I also cut on the bandsaw.
It actually has more fingers but it's a smaller level of detail
and it was a lot quicker to cut
because the fingers were straight.
And, while I'm at it, I thought I'd compare it to a couple of
finer box joints or finger joints.
That I made on my screw advance box joint jig.
These actually were the quickest to cut.
This one being the quickest because I could just use
my regular saw blade.
So, I'm gonna test these on my testing apparatus.
I've got one of the joints already
clamped on to it. And I'm gonna use this jack
to pump this thing up until it breaks.
And I've got this
3 to 1 mechanical advantage on a lever here.
So I can measure the force with my bathroom scale.
The bathroom scale only goes to 300 pounds so I
need that lever thing to cut down the force
so only a third of the force goes onto the bathroom scale
so hopefully, it will still be within range.
And I'm gonna record the weight
that I'm pushing on here with a camera aimed
at my bathroom scale,
so that if I miss the maximum reading,
I'll still have it on video.
So, let's test these joints.
OK, joint number 1.
I've got the bathroom scale...The zero set
so that with the weight of the jack on it,
it actually reads zero. So, I don't have to subtract
the weight of the jack, so now let's start pumping.
Whoops.
20 - 30 - 40 - 50
60 - 70 -80
135 - 140
145 - 150
155 -160
165 - 170
175 - 180
185
This is where it stops.
185
Yeah, that was it.
OK, test number 2.
I've got one of my box joints in the jig now.
So let's see how far this one will go.
150
160
170
I think it's going.
170.
There it goes.
And there's nothing left in that joint.
OK, here's my second dovetail joint.
This time with the camera very close up.
Let's pump this one.
40 - 60 - 70
80 - 150
Yeah.
150
150. It just won't go past that.
150
And now it's completely let go.
Now here's my second bandsaw box joint.
175
180
That's gone.
And it's let go.
And there's no...
Not much residual strength left in that one.
So, overall the dovetail joints and the box joints
did about the same in strength.
The difference is really too small
given the variations for the sample readings to say that
one is better than the other.
So the interesting thing will be how well my
screw advance box joint jig joints do against those.
And now testing
the coarser of the two joints I made with
the screw advance box joint jig.
Now this joint is only half the size of the other joints.
So, if it takes half as much force as the other joints,
it's actually already doing pretty good.
40 - 50 - 60
110
115
120
130
Yeah, 130 is the limit I think.
Yeah, yeah.
And this is interesting,
the joint itself didn't actually fail.
It's that my wood came apart.
OK, now this is the finer of the joints that I did
with the screw advance box joint jig.
Again, it's half the size of my dovetail joints.
So, let's see how it does.
90 - 100 - 105
110
And there it goes.
So that joint is...
Yeah, nothing left on that one.
And once again, interestingly enough,
the joint itself stayed together but the wood came apart.
So, examining the first of my screw
advance box joint jig joints,
I did actually have some of the wood pulling out a little bit.
So, there was a minor amount of joint failure in that one.
But for the finer one, the wood just
plain old tore apart.
So, this is definitely wood failure in this joint.
I really couldn't have made that one any stronger,
with the joint.
Now the piece that actually tore has got a much lighter grain
so it's a lighter, weaker piece of wood.
Which is why that piece failed.
And the other piece didn't.
So, now comparing the overall results.
I put the two different types of box joints from my
screw advance box joint jig in the same column.
And I have to double those because
they're only half as wide.
So, that gives me an average of 240 pounds.
Which is quite a bit more than the other two types of joints.
But, I'm actually kind of impressed with...
how close the other joints came because
the screw advance box joint jigs are about as strong
as you can get before the wood fails.
So that the dovetail and the coarser of the box joints
came to within two thirds of that
is actually pretty impressive.