When it comes to installing shiplap wall panels, having the right router bit is key to getting perfectly milled boards that fit together seamlessly. Shiplap panels have a lip cut along one edge that fits into the corresponding groove cut on the next panel, creating tight, clean lines. Choosing the wrong router bit can result in shiplap boards that don’t interlock properly, leaving unsightly gaps in the finished wall.
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What is Shiplap?
Shiplap is a type of decorative wall covering made from wooden boards with a horizontal lap joint. The boards are milled with a lip or rabbet cut along one long edge, and a corresponding groove cut along the opposite long edge. This allows the boards to be installed overlapping one another to create a flush, even surface. Shiplap can be made from various wood species, but pine, poplar and cedar are common choices for interior use.
The overlapping joint design of shiplap covers any gaps between boards, creating a smooth, continuous look. It provides an attractive, rustic aesthetic popular in farmhouse, cottage, and industrial decor styles. Shiplap is commonly used on walls but can also be installed on ceilings as a wood accent.
Router Bits for Cutting Shiplap Boards
When milling your own shiplap from raw lumber, using the correct router bit is crucial to get boards that fit tightly together. There are a few different router bit profiles that can be used to create the interlocking shiplap joint.
1. Tongue and Groove Router Bit Set
A tongue and groove bit set is the most common choice for milling shiplap. This includes two matched router bits:
- Tongue bit – cuts the protruding lip or “tongue” on one edge of the board.
- Groove bit – cuts the recessed “groove” on the opposite edge to accept the tongue.
When used together, these T&G bits produce the classic shiplap interlocking shape. Tongue and groove sets are available in different sizes to accommodate various board thicknesses.
2. Rabbeted Shiplap Router Bit
Another option is a dedicated rabbeted shiplap bit. This single bit has stacked cutting edges that shape both the tongue and groove in one pass. The top bearings guide the tongue cut, while the bottom bearings outline the groove. This produces a rabbet-style shiplap joint.
A rabbeted shiplap bit simplifies the milling process since a single bit makes both edge cuts. They work well for producing uniform shiplap boards in batch. These bits also come in sizes to match common lumber thicknesses.
3. Dado Stack Shiplap Blade Set
On a table saw, shiplap boards can be shaped with a set of stacked dado blades. You’ll need a blade set intended for cutting rabbets and grooves. Arrange the blades to make a tongue cutting profile on one side of the workpiece. Then flip the wood over and re-stack the blades to cut the groove side.
Table saw dado stacks allow very precise width control for custom sizing the tongue and groove to fit your lumber dimensions. This method requires careful setup but can produce accurate shiplap boards.
Choosing the Right Bit Size
When selecting a router bit for cutting shiplap, the most important factor is choosing the appropriate size for your lumber boards. The bit must be scaled to work with the actual thickness of the wood stock you’re using to achieve a tight interlocking joint.
Standard shiplap board sizes include:
| Shiplap Board Thickness | Router Bit Size |
|---|---|
| 5/8″ | 5/8″ or metric 16mm |
| 3/4″ | 3/4″ or metric 20mm |
| 1″ | 1″ or metric 25mm |
Matching the bit size to the lumber thickness ensures the boards join snugly without unsightly gaps or interference. The tongue and groove should interlock cleanly, forming a flat shiplap surface when installed.
Router Bit Materials
Carbide-tipped router bits stay sharper than high-speed steel bits. They’re ideal for shiplap milling where tear-out and fraying of the wood edge is undesirable. The carbide cutters make smooth, splinter-free cuts in pine, cedar and other shiplap lumber.
For DIYers, solid carbide bits are more economical than carbide-tipped. While not as durable as tipped bits, solid carbide provides adequate edge life for occasional shiplap projects. They produce clean tongue and groove cuts in most common shiplap woods.
Router Bit Shank Size
A 1/2″ shank size is recommended for router bits used to mill shiplap. Large shanks minimize vibration for cleaner, more accurate cuts. This reduces bit wobble that can cause poor interlocking between shiplap boards.
Larger shank bits also feature beefier cutting heads that stand up better for production milling. They remove material faster with less stress for extended bit life.
Chipbreakers and Anti-Kickback Designs
Since shiplap milling involves lengthwise cuts in lumber, look for router bits with features to control chip buildup. Bits with small notches or serrations along the cutting edges help break off waste material during the cut. This chipbreaking action improves chip ejection and bit performance.
Some shiplap router bits also incorporate grooved shoulders or other anti-kickback designs. These reduce the chance of workpiece kickback for safer milling. Combined chipbreakers and anti-kickback features allow smoother planing of tongue and groove cuts.
Bearing Guided Bits
For the most precision results, use router bits with bearings to guide the cut. The bearing rides along the edge of the workpiece or a guide to pattern the profile. This prevents any wandering of the bit for clean, accurate tongue and groove cuts.
On rabbeted shiplap bits, bearings both above and below the cutters maintain proper positioning through the full cutting depth. Guided shank and bottom-bearing bits also ensure consistency when milling batches of shiplap boards.
Best Router Bit Brands for Shiplap
Leading router bit manufacturers offer quality options tailored for shiplap milling, including:
Freud
Freud’s tongue and groove sets provide two perfectly matched bits scaled for common shiplap sizes. Their premier Hi-ATB grind cuts smoothly across changing grain patterns.
Whiteside
Whiteside’s UD2100 series features solid carbide tongue and groove bit sets with excellent edge life ratings for the occasional user. Up-shear spiral bits are also available.
CMT
CMT’s shiplap sets include anti-kickback options ideal for safe production milling. They also offer tongue and groove bits with CMT’s proprietary orange coating for extra smooth finished cuts.
Amana
Known for durable carbide cutters, Amana’s rabbeted shiplap bits make quick work of grooving and tongue cuts in a single pass. Bottom bearings provide workpiece guidance.
Using a Router Table
For best results milling shiplap, use a router table instead of a handheld router. Working on a table provides control and stability when making the lengthwise tongue and groove cuts. Use an adjustable fence to set the exact cutting depth for the profile.
On a router table, the workpiece is stationary while the bit moves, allowing more precise feed control. The stationary setup also allows safer handling of longer boards. Make multiple passes taking light depths of cut to achieve the tongue and groove profile.
Use featherboards to hold boards tight to the fence when cutting. Always feed stock flat against the table surface to prevent rocking and uneven cuts. Work slowly with even pressure to complete the full cut.
Jointing Lumber
For proper shiplap installation, the boards must have straight, square edges. Any cupping, bowing or winding of the lumber will prevent tight seams. Resurface and straightline boards as needed before milling.
Pass boards over the jointer to flatten one face and one edge serving as a reference surface. Then set boards on edge and joint again to square the adjacent edge. This joints both edges perfectly perpendicular for mating the tongue and groove cuts.
Conclusion
A properly shaped tongue and groove is essential for creating beautiful, seamless shiplap walls. Investing in a quality tongue and groove router bit set designed for shiplap will get professional results. Match the profile dimensions to your exact lumber thickness for a perfect fit. Carbide cutters provide a smooth finish, while anti-kickback options enhance safety. With the right router bits, you can achieve stunning interlocking shiplap boards to enhance your next wall project.