Carpenters, cabinetmakers, and woodworkers generally know that there are many ways to butt, splice, or assemble parts for a given project. The key is choosing the right joint for the application at hand.
Sometimes a wooden object can be subjected to great efforts during its useful life (for example, a dining chair, a table, a stool, etc.) and in those cases we can resort to the solidity of the traditional methods of dices, tenon and mortise, or other sturdy joints. At other times, we can make the joints become the “star” of the project, choosing the beauty and symmetry of the joints. dovetails or the unions finger. But when we are looking for a fast, simple and strong enough method for applications subject to light or medium-term stresses, the embossed it is a wise choice.
What is caulking in carpentry?
It is neither more nor less than a join method that uses biscuits. The term may seem unusual to newbies, but, although they closely resemble a real one, in carpentry matters a cracker like the ones we present in this photo, by the way it is not for eating.
The biscuits, also known as flat studs, they are shaped like an oval disc 4 mm thick, they can be made of beech wood, ash wood or compressed plywood and they are sold in various sizes, the most common of which are those shown in the illustration above.
Basically they work in the same way as the dowels or dowels used in other types of joints. The difference is that they are inserted into a groove in the workpiece, previously made with a disc or cutter.
Now why are cookies better than wheat ears? In short, because of the size and shape of the groove. The oversized slot causes the cookie to move slightly, allowing the user to adjust the pieces to be joined so that they are perfectly aligned. When the groove is filled with a polyvinyl acetate (PVA) glue and a pre-soaked cookie in water is introduced, the cookie expands, occupying the entire groove, resulting in an extremely strong joint.
Experts assure that a biscuit board It is ideal for but not limited to table tops, boxes, drawers, cabinet front shells and frames, chamfered corners, edge covering, and as a quick and easy replacement for tenon and mortise joint.
We simply have to mill the grooves in both pieces to be joined, soak the cookies in water, apply glue, place the cookies in the grooves of one of the pieces, assemble, clamp and go. In about a minute, the gasket will be perfectly aligned and strong enough to be used in multiple applications.
So far, everything is great. But now comes an interesting question.
How are grooves milled in wood?
There are some variants to do it. Some workers use circular table saws with dicing blades, while others use portable routers and / or routers equipped with lowered profile cutters for assemblies. All these methods can provide good performances depending on the final use of the obtained gasket.
On the other hand, certain manufacturers offer special accessories that include a disc cutter and a sawdust collection bag, on which a common grinder without its guard and abrasive disc can be mounted. This accessory + grinder combination finds its fans in occasional use, particularly among DIY enthusiasts.
However, many are still unaware that there is a professional electric machine expressly designed to mill grooves in pieces of wood that will be subjected to a biscuit joint. That machine is called joint milling machine or, in other regions and unsurprisingly, simply cookie-cutter. And it’s not new: the professional biscuit joiner was introduced to the market more than 60 years ago and is the tool indicated for this type of work, so it is important that we know it in detail.
What is a biscuit and how does it work?
It is simply a machine fitted with a retractable disc cutter measuring approximately 100mm x 4mm which is protected by a metal casing. The cutter rotates at approximately 10,000 rpm driven by an electric motor, and the cutter guard housing is held securely in its forward position by a spring mechanism. The spring is released by pressing a button to allow the bur to protrude from the tool when in operational mode. The distance the cutter protrudes is adjustable and it is this setting that determines the depth of the groove obtained in the workpiece, which in turn will depend on the size of the cookie used. The grooves produced are arches of the same radius as the cutter, so the more the cutter protrudes, and consequently the more it penetrates into the wood, the deeper and wider the groove becomes.
Main components of the biscuit machine
Let’s take a brief look at the most important elements of a typical biscuit machine and learn what each one does.
1. ON / OFF switch: turns the machine on or off. On some models it is designed to disconnect power more quickly in an emergency.
2. Engine: typically 800-1000 W or 6.5 A (depending on the model), it spins up to 11,000 rpm. The motor housing also acts as a handle to push the tool forward and mill the groove in the wood.
3. Motherboard: on some models, it is designed to be screwed onto a workbench, so that the biscuit joiner can be used as a tool stationary for milling grooves in a large stack of parts using jigs.
4. Angle scale: shows the angle of inclination of the fence, which can be between 0º and 90º, as indicated in the following figures.
5. Screw for adjusting the angle of the fence: locks the fence at the angle indicated on scale 4 to mill the grooves.
6. Vertical center mark: indicates the vertical center of the cutter, that is, the center of its axis.
7. Stop-guide: It can be adjusted in height (screw 8) or in angle (screw 5). It rests on the top of the workpiece, keeping the tool stable and placing it at the right height to mill the wood. It also has markings to facilitate alignment with the markings made on the workpiece.
8. Screw for adjusting the height of the fence: the height is indicated on a scale starting at the center of the cutter’s thickness. On some machines, the fence must be adjusted manually and then locked with a lever. Other models have a screw that raises the fence using a rack and pinion system.
9. Depth of cut adjusting screw: The depth of cut can be adjusted according to the size of the cookie used. It ranges from 8mm to 12.3mm for the most common cookie sizes and can go up to 22mm using specialty cutters.
10. Cutter lock button: prevents the bur from rotating when changing.
11. Handle: provides a secure grip and precise control of the tool.
12. Adapter for suction system: Allows you to connect a dust bag or vacuum cleaner to the dust collection port on the side of the tool, to collect sawdust while working.
13. Dust bag: on many models it is supplied with the tool.
Cutter: usually has 6 to 8 teeth and remains within the tool when not in use. Connected to a spring mechanism, it comes out of its slot when the body of the tool it is pushed into the workpiece, and then automatically retracts.
Types of cuts made with a biscuit machine
We can use a biscuit maker to make a variety of invisible joints quickly and accurately. Some examples are those provided in the figure below.
1. 90 degree joint: ideal for joining parts to be stressed in a certain direction, for example a drawer.
2. Miter joint (45º): The advantage of this type of joint is that it provides a clean finish, ideal for the construction of furniture, boxes, frames, etc.
3. Butt and parallel joint: It is used to join pieces at their ends (butt) and to widen them (parallel), for example, when we assemble the board for a table.
4. Frame joint: provides a solid, professional-looking bond.
5. T-joint: It is used to fix a shelf or a center section to a piece of furniture.
Accessories of a biscuit machine
Since we will be making joints with biscuits, it is therefore essential to have the correct biscuits before starting to work. We can buy them in bags or tubes / jars, classified according to their size.
To obtain a solid joint, it is advisable that we always use the largest possible biscuit size for the thickness of the wood, that is:
- Number 0: for pieces 8-12 mm thick
- Number 10: for pieces 12-15 mm thick
- Number 20: for parts thicker than 15 mm
If the piece is more than 25 mm thick, the ideal is to make two slots, one on top of the other, and use two cookies.
We must also have the right glue, and a pair of clamps will certainly be very useful to keep the pieces that we have just joined firmly together.
Why should I use a biscuit joiner and not a portable router or router?
First of all, because it is difficult to insert a cutter with a recessed profile (the cutting tool used in routers to mill grooves) into the edge of the part to be grooved in such a way as to achieve forever a perfect perpendicularity to said edge. In addition, many experts consider this method not only too slow, but also extremely dangerous.
Instead, a biscuit maker Eliminate these concerns. The cutter, which rotates at high speed, as we have seen, is completely housed within the protection of the tool until it enters the workpiece. Second, the guidance system of the biscuit maker it practically guarantees that the milling is always perpendicular to the edge of the piece, which ensures a consistent and fast fit.
For those who want to see in detail a biscuit maker, know its parts and especially check its operation, this video provides an excellent illustration.