Biscuit joints are less popular among the types of woodworking joinery. These joints do not have many applications compared to other wood joints. The name derives from its ability to form timber into biscuit shapes, where the joints connect. Its primary purpose is to connect large boards like in constructing table tops. The biscuit-like timber keeps large wood pieces from swaying. The wood pieces prevent racking by adding strength to the woodworking project. The outcome of your project looks aesthetically appealing if the biscuit joints are correctly tight.
What is a Biscuit Joint?
A biscuit joint is a joinery technique popularized in the 1950s. It refers to a piece of oval-shaped timber that woodworkers insert into slots of two wood pieces where the biscuit connects.
The biscuit looks like a football that expands after gluing to create a snug fit and seamless joint. It would be best if you had a biscuit or plate joiner to cut the slots to fit in the biscuits. The biscuit joiner consists of a small circular blade that dives into the timber, creating a crescent-moon slot.
Biscuit joints look stunning with their concealed joinery if you align the biscuit joinery properly. It is one of the perks that attract woodworkers to choose it for some applications. Biscuit joint works similarly with a butt joint, in which the latter is a product of butting two timbers.
The biscuit and butt joint are weak joineries, but you can reinforce them by combining them with glue. Biscuit joints rarely malfunction if you carefully align the tool, and they could be more robust than wood pieces.
You can use laminated wood products or solid wood to create biscuit joints. If you want a good quality biscuit, laminated woods are a good choice as the glue’s moisture encourages the biscuit layers to swell and expand.
What are the Sizes & Settings of Biscuit Joints?
Biscuit joinery works best if you use beechwood, though you can use other types of wood. Beechwood is robust and excellent for creating different standard biscuit sizes, such as number 0, number 10, and number 20. The bigger the size is, the stronger the biscuit. All biscuit joineries have the same thickness, which is 5/32 inches, and they come in four sizes (width/length), such as:
- No. 0: 5/8-inch x 1 3/4 inches (5/8 inch wide, 1 7/8 inches long)
- No. 10: 3/4-inch x 2 1/8 inches
- No. 20: 1 inch x 2 3/8 inches (15/16” wide, 2 ¼” long)
- No. FF: 1/2-inch x 1 3/8 inches long
Number 10 biscuit joiners are a standard size suitable for framing. They are always available in hardware stores as they are more saleable than other sizes.
Number 20 biscuit joiners are famous when working on particleboard and plywood. Most tabletop projects use the number 20. Projects that carry a lot of weight and undergo stress are perfect for this size.
Number 0 biscuit joiners are excellent for joining small workpieces or in areas that do not require a lot of stress. Some projects that can benefit number zero size include picture frames and narrow applications like narrow cabinet door stiles and rails.
Number FF biscuit joiners are usually for small workpieces that do not need a biscuit joiner tool. The standard biscuit joiners can adjust to create a small size for slots. Biscuit joiners are usually adjustable to give way for the three popular biscuit sizes, such as numbers 10, 20, and 0.
Note: An adequately aligned biscuit cutter produces accurate and strong biscuit joints. Biscuit joints are a better alternative than miter joints, corner joints, T-joints, and edge-to-edge joints, especially when creating slots using a plate joiner or biscuit joiner.
What is the Ideal Biscuit Size?
If you want a strong joint, choose the largest biscuit size, number 20. This biscuit size offers extra strength to the biscuit joint, especially if you are working on a large workpiece. Using a narrow workpiece, use a smaller biscuit size for good results. Number 20 is a practical option, but remember that tiny wood and small joints require a smaller number, number 10 or zero.
What is the Ideal Spacing for Biscuit Joints?
The spacing requirements of biscuit joints depend on the woodworking preference. It would help if you placed the plate joints correctly to have the biscuit’s edge at least two to three inches away from the workpiece edge. The workpiece tends to split or crack if it is too close to the edge. If it is too far, it will impact the strength property at the workpiece ends.
After determining the edge biscuits’ position, it would be easier to calculate the spacing between the biscuits’ edges. The ideal spacing should be six to twelve inches from the centerline to keep them strong, especially high-stress joints for cabinet carcasses, small boxes, and accent tables.
It is better to refrain from using biscuit joints if you doubt their strength or want peace of mind. Those woodworkers who have used biscuit joints say they have never experienced joint failure.
Tabletops, boxes, face frames, drawers, cabinets, edge banding, and miters use biscuit joints by using different biscuit sizes to join wood thicknesses. This wood joiner is a good alternative for mortise and tenon joints as they are quick and easy to make concealed wood joints. They are efficient in connecting end to end of wood planks.
Biscuit joiners are excellent for joining fiberboard with medium density, particle board, and plywood. They are suitable for small and medium-sized projects like small cabinets, boxes, and drawers. You can opt for biscuit joiners to connect ninety-degree angled workpieces.
Tips on How to Create Biscuit Joiners
Here are some hacks on how to get started with biscuit joints:
1. Prepare wood planks or timber. Line them up precisely on a workbench. Scribble some lines on the wood using a pencil to mark the area to cut the joints.
2. Clamp the wood piece to a workbench/vice after scribbling the cut’s position. It ensures that the wood does not move when cutting into the biscuit joint.
3. Adjust the biscuit joiner according to the biscuit size of your choice and begin cutting into the wood piece along the area you have marked.
4. Double-check if the wood has appropriately joined before inserting the wood biscuits. Bond the wood pieces together with glue, ensuring the timber clamps well.
Note: Timber biscuits are available at hardware stores. Sand the workpiece if the area where you joined the wood piece is uneven. A handy belt sander works best for this task.
Pros & Cons of Biscuit Joints
Biscuit joints may not be the strongest wood joints, yet they also have some characteristics that make them usable in some woodworking projects. Here are the advantages:
- Quick & Simple: The simplicity of biscuit joints makes them easy to create, even for newbies in woodworking. This technique does not require an accurate measurement compared to other joinery types. Some projects do not even ask you to measure the workpieces. The task does not take long since you only implement two cuts, a little clamping, and gluing.
- Clean Concealed Joints: Biscuit joints look impressive if you do it correctly. The joints are hardly visible even to meticulous people, which leads to a neat and stunning result. This joiner is ideal if you are looking for a perfect alignment, though it does not require you to have an accurate measurement.
- Relatively Strong Alternative: Don’t mind those debates regarding the biscuit’s durability. Woodworkers can attest that if you carefully cut, biscuit joints can offer strength and enduring properties to your wood construction. Use a biscuit joiner to create a sturdy workpiece. It is a good material for some projects that use plywood or fiberwood for cabinetry, picture frames, and boxes. Incorporate a high-quality water-based adhesive to fit the joints properly.
- Affordable: Biscuits are inexpensive joints in various sizes and settings, making them perfect for all projects. They are easy to work on as they are pre-made.
- Offers Natural Look: With the right joinery tools, the biscuit joints look natural once the workpieces join together. Aside from a clean, concealed joint, your project will have a natural finish.
Take a look at the disadvantages of biscuit joints:
- Inaccurate Measurement: Since biscuit joints do not need accurate measurements; it does not yield good results. The biscuits lag in popularity as the strength is questionable, though some woodworkers say the joints succeed if they apply glue.
- Misalignment Issues: This problem stems from the fact that the joints do not need an accurate measurement. It leads to weak joints due to pressure in daily use.
- Split and Cracks: Improper positioning of the biscuit, which is too far or close to the edge, can expose the biscuit from splitting or cracks. You have to follow the allowable distance of the biscuit from the edges of the workpieces.
- Not Strong Enough: The reason biscuit joints are unstable is because they cannot penetrate the wood’s depth after joining the workpieces together. It is inferior to dowel strength, in which the depth comes from drilling deep into the workpiece. Biscuit joinery draws power from expansion and gluing, while dowels get it from the wood’s tensile strength, penetration depth, and adhesive.
Popular Types of Biscuit Joints
1) Miter Joints
A miter joint can hide end-to-end grain when constructing plywood cabinets or solid wood boxes. If cutting long miters, it could be challenging to reinforce and glue.
Using several biscuits can resolve these issues by registering the ends of workpieces to prevent the corners from slipping while clamping them. It also helps reinforce the end grain joint. If your miter has reinforcement from a biscuit, its strength is as muscular as table-saw cut workpieces.
You can hide the biscuits within the miter for an aesthetic and clean look. Miter joints are ideal for picture frames, window and door casings, and cabinetry.
2) End-to-Edge Joints
This type of biscuit joint is a popular option for gluing up tabletops with exact thickness but different width boards. This method provides a solution to join sections of the solid wood end as the workpiece absorbs the glue towards the end grain of the timber.
Incorporating a biscuit joint help increase the gluing surface area by cutting the slot along the wood grain. Wainscoting and furniture use end-to-end joints for efficient contact between two wood sections. Place the timber along the sides of the timber’s end grain in the opposite direction of the first wood piece.
Make a center line for the slots by marking across the biscuit joints with a pencil in every three to six inches. Adjust the biscuit joiner after separating the piece of timber to get the accurate biscuit size. If cutting an edge-to-edge joint, choose the number 20 size.
Align your cutting guide by following the pencil mark after placing the guide fence on the wood’s top. Start sawing while holding the guide fence when the motor runs at full speed. Slowly plunge the blade into the timber until there is no more space to push and withdraw the blade thoroughly.
Apply a thin layer of glue to one edge of the slots, then insert the biscuits. Apply glue on the opposite edge of the spaces to connect the two wood pieces. Repeat the step for the next pencil mark.
3) Offset Joints
This biscuit joinery type creates a clean look if you join a rail to a leg. To make an offset biscuit:
1. Use a biscuit joiner guide fence to mark the apron and leg for the slot. The spacer should have the same thickness for your desired offset.
2. Place the spacer beneath the jointer, place the leg’s show face against the workbench, and start cutting the slot.
3. When you cut the apron’s matching slot, take out the space, and create a slot at the board’s end, ensuring that the show face is in direct contact with the bench.
Other types of biscuit joints are edge grain to edge grain, butt joints, and double joints. Edge grain to edge grain is the most popular biscuit joineries, especially in joining the flat parts of tabletops.
Double joints add extra strength to the joint by cutting the slot twice and adjusting the jointer after cutting each slot to give way to the two biscuits that belong to the same slot.
Butt joints are less popular as they are weak. Adding biscuit to the end-to-end butt joint help reinforce the joint due to the sizeable gluing surface.
Biscuit joints have different types of strengthening weak joints. They come in various sizes and setting for your desired joinery—the larger the size number, the better the quality of the joints. Working on small workpieces requires a small size number. Biscuit joinery is an alternative if you are looking for quick and well-aligned joinery.