Hi there! My name is Marie and today I'm going to show you how to make the
perfect half lap joint, whether it's on an end like this or in the middle.
Until recently I've used different methods to make half lap joints.
I've tried using my table saw with my miter gauge I've used my bandsaw. I've
even used chisels and done them by hand and what I found is every single time the results
have been very inconsistent never getting that perfect accurate joint like
on these. You want to get them nice and flush nice and perfect. I'm never getting
accurate results when I use these different methods and it becomes really
frustrating when you need to make repeated half lap joints. So what I did is I
did a little research and I came up with a method that you can use to get
accurate and perfect results every single time you make a half lap joint.
Now all you'll need for this is a crosscut sled for your table saw, a
combination Square, and you'll need the secret ingredient which is this little
piece, and I'll show you how to make one. So let's get started. The key to this
method is to make a custom spacer the exact same thickness as your saw blade.
Start by squaring up your piece of wood using your crosscut sled then cut a thin
strip about an eighth of an inch thick.
remove the crosscut sled and then find two scrap pieces of plywood that you'll
sandwich the blade in. the goal is to try to fit the spacer in between the
sandwich. it likely won't fit so just use some sandpaper on a flat surface to sand
it down until it fits between the plywood. the goal is to have a
perfect fit the first step to cutting a perfect half lap joint is finding the
exact midpoint between the top and bottom of your board while you can
certainly measure the thickness and divide by half this can sometimes be
impractical and lead to slight error an easier method is using a combination
square. set it to roughly half the thickness of the board then trace a line
starting from the top of the board flip it over and do the same from the bottom
the goal is that the lines should be perfectly one on top of each other if
not adjust the combination square until they are perfectly aligned and now you
found dead center next it's time to adjust the blade
height with your crosscut sled in place slowly raise the blade until it creeps
up close to the line but is still beneath it it's better to slowly adjust
upwards than to cut too deep on the first pass using a scrap piece of wood
with the same dimensions as your workpiece shave off one end then flip
over the piece and repeat on the other side. You should be left with a thin
shaving in between the two cuts so gently raise the blade and repeat once
again notice after one pass I'm left with the thin razor thin piece here
that's exactly what you want on the second pass it completely disappears
this is the perfect height of the blade
the method is similar whether you're cutting half flaps on the end of a board
or in the middle I'll start by showing you how to cut them on the end you'll
need both work pieces start by setting your second one the one that we're not
cutting into up against the blade and then but a stop block up against it and
clamp it to your crosscut sled then you can remove that second workpiece and
place your spacer up against the stop block next but your workpiece the one
that you want to cut into up against your spacer and make the cut
then you can remove the spacer and make repeated cuts between the initial cut
that we made up until the end of the workpiece take your time with this the
goal is to make the cuts as close together as possible while watching your
fingers and it's a good idea to keep the stop lock in place because you'll likely
be able to use it in the same position for the second workpiece in theory they
should be the same dimension it's also a good idea to mark your spacer to make
sure you don't throw it out or you don't lose it because I'll want to use it
again and again after repeating the cut for the second piece you may find that
the fit isn't exactly perfect pretty close but not perfect you'll need to
smooth out the bumps left by the blade just by lightly sanding each of the work
pieces and then dry fit again and you should find the fit to be absolutely
perfect let me tell you I am so happy with this I can't tell you how many lap
joints I've made and been frustrated with the results so I am so pleased with
this method every single time you get perfect accuracy alright so that was for
making half lap joints on the end of a board now I want to show you how to make
them in the middle so essentially the steps are the same to start off you have
to find the midpoint of your board but then you want to mark where you want to
have your joint so I'm gonna have them about two inches in from each of the
board's so I made that mark and then I'm gonna use that as a reference you want
to line it up with the right side of your crosscut sled kerf then you'll
want to butt up the second workpiece perpendicular to that
and then squeeze in your stop block which you will clamp to your fence once
you're all set up and ready go ahead and make the first cut once you've made the
cut you can go ahead and take the second workpiece out of the way and replace it
with your custom spacer and then you'll want to butt the workpiece up against
the spacer and hold that down tightly and then make your second cut
you now have both outside cuts for your half lap joint all you need to do now is
remove the material that's left in between those two lines so I hope you've
enjoyed this video and you found it useful I know I sure learned a lot
making it myself and if you did like this video please hit that thumbs up
button and subscribe to my channel for more DIY videos to come just as before
when we were doing the half laps on the end of the boards you'll find out the
fit isn't exactly perfect right off the table saw this is an easy fix though
with some sandpaper you can smooth out those bumps left behind by the saw and
just lightly smooth the inside of each of the cuts and then you'll find that
the fit is absolutely perfect