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Detailed Biscuit Joiner Tutorial
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Jan 25, 2024
Learn exactly how biscuit joinery works in this detailed and in-depth biscuit joiner tutorial. Biscuit joiners are extremely useful woodworking power tools designed to join wood strongly and invisibly. They do this by cutting a custom-sized groove in each of the wood surfaces being joined, allowing the installation of a thin, oval-shaped piece of wood meant to join the two together. These thin pieces of wood are called "biscuits". Learn all about biscuit joiners as I take you on a tour of these remarkable tools and show you just how useful they can be.
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0:00
In this video, I want to introduce you to biscuit joinery
0:04
It's one of the simpler ways of joining wood, and I think it makes a lot of sense for beginners
0:11
It may not be the first thing you want to attempt, but biscuit joinery is very versatile
0:17
and it's easy to succeed at. And I'm going to show you what it's all about
0:22
We're actually going to do a biscuit joint. I'm going to fill you in on some of the tips that I've learned over the years
0:27
But to begin, let's just take a look at these containers I've got here
0:31
In the world of woodworking, these are called biscuits. And they're factory-made, oval pieces of wood, hardwood, of different sizes
0:44
And the purpose of the biscuit is kind of like the purpose of a dowel
0:50
in that it fits into neighboring pieces of wood, and it spans the gap between them
0:57
So if we wanted to join this piece of wood to this piece of wood like this
1:01
we would use a biscuit joiner, which is a special tool meant to cut slots for biscuits
1:10
We would cut a slot here, a matching slot in the other piece
1:16
and then we would swab some glue into the slot, put the biscuit in
1:21
and then swab some glue in this slot, and fit it over
1:25
And the biscuit spans the joint between the two pieces of wood
1:30
and creates a strong joint that's kind of really pretty easy to manage
1:36
A couple of things before I go on. As you can see, the biscuits come in different sizes
1:42
The bulk of biscuit sizes are described with numbers. And kind of the standard, large-ish sized biscuit is the number 20
1:52
And you can see that number 20 stamped right in there. There's also number 10, which is a little smaller
2:01
And these ones are... it doesn't say on this particular one, but this is a number zero
2:08
So these are the three common sizes. Most people don't use anything other than these
2:15
Biscuit joinery is incredibly versatile, and part of that versatility comes from the fact that there are more biscuits than just these
2:25
Like these whoppers, for instance. These are actually big enough and strong enough that they're rated for supporting stair treads
2:35
where those treads meet another piece of wood. So, really big one here
2:42
Let's take a look at this. This is really kind of neat
2:49
These are biscuit hinges, believe it or not. So, you cut a slot in the wood, two pieces of wood that you want to be hinged together
2:58
and these hinges are made to go in that slot and to lock in there
3:04
There are these interlocking pieces of metal. So, these would fit into biscuit slots, cut with the biscuit joiner
3:18
but this is for when you want to have parts that temporarily interlock
3:22
So it would kind of slide together, move over, and now the two pieces of wood are locked together
3:31
There are plastic biscuits as well, for applications where you might be joining pieces of plastic together
3:43
like Corian countertop, for instance, any of those synthetic solid surface countertop materials, things like this
3:53
So, really quite a variety. You may notice the name Lamello here
3:58
There's a story behind that. Biscuit joinery was invented in 1955 by a man in Switzerland
4:08
and he had the technology all patented and everything. So, when I first got seriously interested in woodworking in the early 1980s
4:18
the only kind of biscuit joiner you could get was Lamello, and it's Swiss, it's patented, very expensive
4:25
You could not get, at that time, a biscuit joiner that cost less than $500 or $600
4:32
Money is worth about at least twice as much as it was then
4:36
So, you were looking at paying more than $1,000 for a tool, pretty much like that one
4:42
Hardly anybody did. That's why biscuit joinery was not really on the radar
4:49
until those original patents expired. And now, all of a sudden, every company could make a biscuit joiner, and they have
4:59
Different companies have them. Prices have plummeted. As I recall, the first non-Lamello company that made a biscuit joiner was Freud
5:09
And when I first saw it, I thought, man, that's just a silly, an excuse for joinery
5:18
It's not really legitimate at all. Then I went to work for a man named Stephen Harris
5:25
He was called by Fine Woodworking Magazine as Canada's preeminent maker in wood
5:31
So he was a custom furniture maker, went to work with him, wanted to learn from him
5:36
One of the first things I did for him was to put some things together with a biscuit joiner
5:40
And I thought, well, it's good enough for Stephen Harris, maybe I should look at these again
5:44
And I did, and I use biscuit joints regularly right now. So I want to show you a few alternative ways that biscuit joinery can be used
5:56
But before I do, let's just complete an ordinary, everyday biscuit joint of the sort that you might complete in your work
6:05
So now I want to show you how to join these pieces of wood in this fashion using biscuit joints
6:13
So you could probably guess this is the orientation we would want to do things if we had a cabinet, bookcase, wall shelf, all kinds of things
6:24
So we're going to join these at 90 degrees. Biscuits are great at that. I've used biscuits for many years, even for big wardrobes, held together with nothing more than biscuits like this
6:35
But before we get going, we need to test our machine. Now, I'm going to unplug. Always unplug when you're touching the business end of woodworking tools
6:47
This is how it works. You put this down next to the wood, and then you push on it
6:53
And look what happens. A blade comes out. Now, the blade is just the right thickness that it makes a groove that's the same size as biscuits
7:06
So we don't need to change that. That's a given with the blade. The blade matches the biscuits made that way
7:12
What we do have to wonder about is how deep of a slot that's being cut
7:19
It's going to be a curved bottom slot, of course, because this is a round blade
7:24
And the diameter, the curvature of the blade matches the curvature of this biscuit
7:31
But we don't want the slot to be too deep. Ideally, what we want is the slot to be half as deep as a biscuit
7:41
because one side of the slot is going to be in one piece of wood, and the other side of the slot is going to be the other piece of wood
7:48
Now, if you remember from the doweling video, one of the causes of trouble was when we didn't have a dowel hole that was deep enough
7:58
So the dowel is between the joint. We try to put the joint together. The dowel is too long for the holes you've got, so it's going to keep the joint apart
8:05
The same danger exists with biscuits. In practice, and I'm going to show you this in a second, we want, before you ever put this tool onto any piece of wood that matters
8:18
you have to test the depth of cut. And what we want is a depth of cut that puts just a little bit more than half the biscuit width in slot depth
8:30
Now, why a little bit more? That's because we're probably not going to hit it right on
8:34
If I try to hit it right on, and I'm just not quite deep enough, it's going to hold the joint apart, and that's not what I want
8:41
So I want just a little bit more slot depth than I need, so that there's no interference that way
8:47
Now, by the same token, on the other hand, I don't want the slot to be too deep
8:52
Let's say I make the slot so deep that three-quarters of the biscuit, from here to here, is contained in the slot
8:59
Well, that's going to reduce joint strength, because now there's far less biscuit on the other side of the joint
9:06
So, as you can see, it's kind of a balancing act. It's not a big deal, though, to adjust things properly
9:12
All biscuit joiners have a depth adjustment, and you can see here, there's a little red mark there, and then the number 20
9:22
So, theoretically, I've got this thing adjusted for a number 20 biscuit, but there is a fine adjustment here
9:30
So this is technically, theoretically, what it's supposed to be, and you can see when I push it together
9:36
that little, this rod hits against the stopper and limits the depth
9:42
It's been a while since I've used this biscuit joiner, so I'm not going to trust that this fine adjustment is correct
9:48
Instead, I'm actually going to plunge a biscuit into some scrap. I'm going to put the dowel, or the, put the biscuit in, and then we're going to see how deep we've gotten
9:59
So, just plug back in. I like my earmuffs. You should, too. It just makes life a lot easier, and it protects your hearing
10:10
No huge reason to use safety glasses for an operation like this, but might as well
10:16
And, just to be safe, and let's just plunge this lot and see what we come up with
10:32
So, there's our curved bottom slot, and here's our biscuit. Let's see what happens
10:50
Okay. How do we know we're halfway, or how do we know how far we've gotten
10:55
Well, make a pencil line, flip the biscuit over, and make another pencil line
11:07
So, the distance here is twice the amount of extra biscuit depth
11:17
That's a little bit too much, actually. I'm going to tweak that fine adjustment so that these lines are closer together
11:24
Maybe here and here. Because don't forget, this line here I drew when this side was in the slot all the way
11:36
and this line I drew when this side of the biscuit was in the slot all the way
11:41
So, I just need to make that slot a little bit shallower, and then I'm going to try again, so that we can proceed with confidence
11:51
So, I've just grabbed a wrench of the right size. It's 7 16ths of an inch in this case, and I'm going to loosen the lock nut
11:57
Different machines are going to adjust differently, but they will all have some sort of a depth stop
12:03
As you recall, I want the slot less deep, so that means I'm going to be extending this a bit
12:13
It's a trial and error thing, really. I don't know if that's the right adjustment or not
12:20
I'll lock it there. Let's give it another try. Flip it over
13:01
I like that. I didn't draw the lines quite parallel, but yeah, I think that's going to be fine
13:08
So, now we know we can trust the setting on this machine
13:15
and now it's time to focus on our work pieces, such as they are
13:24
As you could imagine, we want slots here in this piece, and we want matching slots in the ends of this piece
13:34
And the very best way to do that is by using the pieces kind of as their own fence or their own guide
13:44
So, let's say I wanted this shelf member right there. My first step would be to mark that
14:04
So, this is the way I want it to be, and the easiest way to cut the slots I need is to have this in position
14:13
but then just tilt it down so I'm still lined up with the pencil marks I made before
14:25
I have to clamp all this together, too. Actually, let's go around here
14:53
So, that's not going to go anywhere. I'm solid and reliable. Now I have to decide how many biscuits and where I'm going to put them
15:11
Something this narrow could be fastened with one, but I'm going to use two
15:21
So, our next step is to mark where the center of the biscuits would go
15:31
We don't have to be perfectly exact about this. There's that one
15:43
And that one. Now, let me explain what I'm going to do before I do it
15:54
Every biscuit joiner has some kind of a mark on it that shows the middle of the arc of the blade
16:04
So, there's the mark there. There's the corresponding mark here. I'm going to use the marks on the machine to follow the marks that I have made right here
16:21
So, my first operation will be to line up the machine with that first mark and plunge a slot
16:31
And then move over, line up the mark on the machine with the other mark, and then plunge another slot
16:40
Now, that gets me slots in that end, in the ends of that first piece
16:46
But in order to make slots on the other piece, I'm following the same thing
16:54
You see there's a line here. There's a red line. It's also been extended a little bit higher so you can see it
17:01
That lines up with the pencil mark here, and then also further over
17:12
And I'm going to plunge down. That will give me exactly corresponding slots right there on the other side
17:22
So, let's switch on and get going. So, let's unclamp things and we'll see how we did
17:58
These biscuits are close enough that the slots kind of overlap in a way. No matter though
18:09
Biscuits fit in here, and then they fit in here. And we've got our joint. It's a dry fitted version of it anyway
18:22
Nice tight fit. Exactly where we wanted it to be. Now, as with the dowels, when we're actually assembling this, we want to squirt glue in the slot..
18:36
...work it around with a little sliver of wood, brush on some glue with a flux brush on this biscuit..
18:44
...and basically apply glue to the slot and the biscuit, and then assemble the joint and clamp it tight
18:54
And you're going to have a really nice result that way. Like I said before, gluing biscuit joints is pretty similar to gluing dowel joints..
19:02
...in that the first step is to inject some glue in there and spread it around a bit
19:10
That's too much, so I'll put some in the next slot over
19:27
I'm going to put some in here too. These bamboo skewers are very handy for all kinds of things in the shop
19:48
Toothpicks work well too, but the bamboo skewers are great. And now, the biscuit itself
20:05
The old trusty plumber's flux brush. Normally used to apply acidic paste to copper pipe joints, but works great for glue too
20:23
You have to work fairly quickly here. The biscuits have that cross-hatched pattern on them that you've noticed
20:32
And that's because, as with fluted dowel pins that you buy ready to use, these are compressed
20:41
And they swell up in contact with water-based glue. Now I just put a little bit on this half of the biscuits
21:14
We've already got glue in these other slots. It's just a matter of putting it together
21:24
And of course, I would clamp it. I will clamp it. If this was a regular project, there would be an upright over here, one here, maybe another couple down there..
21:38
...and another piece on the other side to make a complete cabinet-like box
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That's usually the way things go. So you have to move fairly quickly. If your project is much larger than this, you might want some help..
21:51
...for applying glue so you can get everything together properly. The main thing you want to avoid is getting your project partially assembled..
22:01
...and then the glue starts to grab, and the biscuits don't want to go together properly
22:06
That's when a nightmare kicks in, so you'll want to get some help to avoid that
22:11
Oh, one other tip as far as biscuits go. It's dry right now
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We've endured an entire Canadian heating season, and that makes the inside of our homes and workshops very dry
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So our biscuits are dry, and they're also relatively thin. If this was August and we'd had several months of humid weather, those biscuits might be too tight to easily go in the hole..
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...even when they don't have glue on them. If that's the case, no problem. You just take your biscuits, put them in the toaster oven at 350 degrees for 15-20 minutes or so..
22:45
...let them cool, and you'll find that they've shrunk right down, and they're ready to be used again
22:50
So this is a typical biscuit joint. Now I want to show you a couple of applications that are a little out of the ordinary
22:57
But I like them a lot, I use them a lot, and I think you'll enjoy them too
23:02
Biscuits don't necessarily have to be installed in the way I just showed you, although that's probably the typical way
23:09
Let's say you've got a 45 degree joint like this. This is called a miter joint
23:14
And maybe you're dealing with some flat stock like this, or maybe it's a molding that's got some detail to it
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What I like to do is to assemble a joint like that with glue and clamps only
23:30
That way I can get the parts lined up properly, there isn't any mismatch, and I get everything just right, and I let the glue grab and dry
23:40
And it's going to hold these two pieces together, kind of. It's not going to have as much strength as I want, though
23:47
And so that's where this comes in. You can plunge biscuits from the unseen back of certain parts in order to strengthen them after they're assembled
24:01
It works great. This is what it looks like when you're done
24:05
And you can sand or saw the biscuit flush just so that it doesn't get in the way
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Now that's not very pretty, of course, and it can never be made pretty
24:15
But that's no matter, because in an application like this, it's a hidden face
24:20
So you're not seeing it at all. Another application might be something like this
24:27
If you can imagine this as, say, a door frame. There might be a raised panel in here, and there's going to be four sides
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Cabinet doors are often made this way. You have a frame around the outside
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The vertical parts of the frame are called stiles, and the horizontal part of the frame is called a rail
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So you have to join them together somehow. Now, there's a slot in here in this particular example, because that's where a panel would go
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Well, two biscuits plunged into the mating parts does a really good job of holding this together
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Now, you're not going to glue a biscuit on the face like this. I've just glued it on here so you can see what's going on
25:11
But this is what's going on inside these two slots. The reason why the biscuit stuck up and was sawn off was because I didn't have enough room for a slot that would be long enough to accommodate a whole biscuit
25:29
because the parts just aren't that wide. But I don't need to accommodate the whole biscuit
25:35
I can accommodate just most of it, like I've got here. A powerful technique works great
25:43
Just another couple of little things. A while back, Craftsman made a wonderful little mini biscuit joiner, which is still kind of legendary, actually
25:54
The last time I looked, they weren't making this anymore, but you could still buy them on the secondary market, like eBay and things like that
26:02
The beauty of this is that it's very well suited to fine work, where the regular biscuits would be too large
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So fine, small woodworking, or even fairly large model making, where you're building, say, a radio-controlled airplane out of small pieces of wood
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these biscuits can do a great job. You can see they're much smaller than the biscuits I showed you before
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Smaller in size and thinner in cross-section. And they only work with this tool here
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But it's worth looking for, and you should know about it in case you run into situations where you need some small biscuits and the regular ones are just too large
26:46
This is kind of interesting. Remember I told you Lamello invented biscuit joinery
26:50
They have a lot of accessories. This is something that I only use when I'm going to be doing a lot of biscuit joinery, because it does speed assembly quite a bit
27:00
It's a glue injection bottle that actually goes into the slots right here, and you pump the glue in
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So it gets the glue right in nice and quick, so that you have as short an assembly time as possible
27:19
But there you have it. Biscuit joinery, definitely something a beginner should look at
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