Can you do biscuit joints with a router?

Routers are versatile woodworking tools that can be used for many applications, including making strong and accurate wood joints. One type of joint that routers excel at is the biscuit joint. Biscuits are small football-shaped pieces of compressed wood that help align boards edge-to-edge and add strength to the joint.

What is a biscuit joint?

A biscuit joint is a type of wood joint made using an oval or football-shaped piece of compressed wood known as a biscuit. The biscuits slots are cut into the adjoining boards using a biscuit joiner or a straight bit in a router. Glue is applied in the slots and the biscuit is inserted, aligning and clamping the boards. Once the glue dries, the biscuits swell, creating a strong, invisible joint.

Biscuit joints are very useful for joining large panels such as tabletops and doors because they help align the boards perfectly. The swelling action of the biscuit also makes the joint stronger than just an edge-to-edge glue joint. Biscuits can also reinforce miter joints and allow for quick alignment of boards at 90 degree angles.

Benefits of biscuit joints

• Align panels and boards perfectly
• Add strength to joints
• Create quick 90 degree joints
• Reinforce miter joints
• Concealed joint

Making biscuit joints with a router

While biscuit joints are most commonly made with a specialized biscuit joiner tool, it is possible to make them with just a router and a straight bit. Here is the process:

Materials needed

• Router with straight bit
• Wood boards for joined panels
• Biscuits
• Clamps
• Wood glue

Cutting the slots

To cut the biscuit slots with a router, you need a straight bit with the correct diameter to match the size of biscuits you are using. Consult the biscuit package for slot width.

Mark the center points for all your biscuit slots on the boards. Be sure slots on adjoining boards align.

Set biscuit slot depth on router equal to half the thickness of the biscuit. Make test cuts on scrap first.

Clamp boards securely and cut slots by moving router across boards at center marks.

Slots on opposite boards should align and be consistent depth.

Gluing and clamping

Once all biscuit slots are cut, apply wood glue into the slots on both boards. Insert biscuits and align boards.

Use clamps to apply even pressure and ensure good alignment while glue dries.

Wipe away excess glue squeeze-out before it dries.

Tips for making biscuits joints with a router

Here are some helpful tips for successfully making biscuit joints with your router:

• Make sure your router bit and biscuits match in size
• Cut test slots in scrap first to dial in slot depth
• Mark all slot centers accurately before cutting
• Clamp boards securely and cut slots slowly
• Use care when aligning boards to keep slots matched
• Apply clamping pressure evenly to get good glue bonds
• Biscuits swell, so don’t overfill slots with too much glue

Common problems and solutions

Despite best efforts, there are some common problems that can occur when making biscuit joints with a router:

Slots not aligned

This is caused by inaccurate marking or movement of boards during routing. Use a biscuit alignment jig or double check marks.

Uneven depth of slots

Can be caused by wobble in router bit or inconsistent feed rate. Make sure bit is secure and move router smoothly across the board.

Loose joint

Results from poor glue coverage in slots or inadequate clamping. Brush glue thoroughly into slots before adding biscuits.

Excess glue squeeze-out

Happens when too much glue is applied. Wipe away excess glue before it dries to avoid having to sand later.

Conclusion

While biscuit joiners provide the most convenience and precision, it is certainly possible to make biscuit joints using just a router and some care. The keys are using an appropriate straight bit, accurate marking, and getting the proper fit when aligning and clamping the joint. With attention to detail and some practice, strong and invisible biscuit joints can be made with only a router.

Biscuit Size	Slot Width
0 (smallest)	5/32 in
10	13/64 in
20 (largest)	17/64 in

Related Questions

What is the best type of bit to use in a router for cutting biscuit slots?

The best type of router bit for cutting biscuit slots is a straight bit with multiple flutes. 2 or 3 flute straight bits work well. The diameter should match the size of the biscuits being used. Carbide tipped bits stay sharper longer when cutting across the grain.

Should I use a fence with my router when cutting biscuit slots?

It’s generally recommended to use a fence attachment on your router when cutting biscuit slots. The fence helps guide the router in a straight line and at a consistent depth across the workpiece. Clamp stop blocks on the fence to make multiple slots at the same width quickly and accurately.

What size biscuits should I use for jointing a tabletop?

For most tabletop panels made from 3/4 inch thick boards, #20 biscuits are recommended. The large size provides maximum strength to keep tabletops flat and rigid. Use at least 4 biscuits spaced evenly across the joint between boards for best results.

Can I make biscuit joints with a handheld power planer?

It is generally not recommended to try making biscuit joints with a handheld planer. These tools are designed for surface planing and do not offer the precision or depth control needed for cutting biscuit slots accurately. For best results, use a router or dedicated biscuit joiner.

Should the biscuit slots be centered in the board thickness?

For maximum strength, biscuit slots should be centered in the thickness of the adjoining boards. If using boards of two different thicknesses, center the slots in the thinner board and adjust slot depth accordingly. Centering allows even glue spread and swelling pressure.

Can I use a biscuit joiner to make mortise and tenon joints?

No, a biscuit joiner should not be used to make mortise and tenon joints. The plunge cutting action and oscillating blade are designed specifically for cutting biscuit slots, not mortises. For mortise and tenon joinery, use a router and straight bit or hollow chisel mortiser for best results.

Is there a quick way to mark the centers for all the biscuit slots at once?

Yes, you can make a spacing block to quickly mark multiple biscuit slot centers. Cut a block the length of your desired biscuit spacing. Then use this block between marks to speed up layout. Be sure to account for the offset of the biscuit joiner fence when marking with your spacing block.

Can I use wood glue to attach biscuits into the slots?

Yes, standard wood glue like PVA or polyurethane glue works well to adhere biscuits into their slots. The glue swelling action of the biscuits combined with a good wood glue bond makes a super strong joint. Just avoid getting excessive squeeze-out in the slots when gluing.