Advanced Router TechniquesUpdated: Nov. 29, 2022
Go beyond the basics: Use your router to make strong joints, plane edges, cut smooth curves and more
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Biscuit joinery without a biscuit joiner
Cutting biscuit slots
Cut slots for biscuits with a slot cutter mounted on an arbor that’s equipped with a bearing. Cut a continuous slot on boards thicker than 3/4 in.
If you want to make biscuit joints, you don’t have to buy a biscuit joiner. In most cases, a router equipped with a 5/32-in. slot bit can cut perfect slots to fit the biscuits. Mark the biscuit positions on both adjoining boards as you would with a biscuit joiner. Then cut a slot that’s about 1/2 in. longer than the biscuit. On thick boards, you don’t even have to mark out anything; just cut one quick, continuous slot on each board. Add glue and biscuits and then clamp it to create a strong joint.
There are two situations where a router can’t substitute for a biscuit joiner: A wood router can cut slots only along the edges of a board, not across its face; and it can only cut along square edges, not beveled ones. Most slot cutters cut slots about 1/2 in. deep, which suits No. 20 biscuits. If you want to use smaller biscuits, buy a kit that includes three bearing sizes for No. 0, No. 10 and No. 20 biscuits (available online and at woodworking stores).
Homemade base plates add versatility
Custom base plate
Make a base plate for use with a trammel, stretcher or other jig from 1/4-in. acrylic.
When I get a new router, the first thing I do is explain to my wife why I need yet another power tool. The second thing I do is remove the plastic base plate. Then I make a plate that’s a few inches larger than the original from 1/4-in.-thick acrylic. I use the original plate as a template to position the screw holes and the center hole. Acrylic has sharp edges, so I round them slightly with sandpaper. In about five minutes, I have an oversized plate that I can fasten to a trammel, stretchers, or any other jigs I dream up. One of my routers is mounted on a 12 x 12-in. piece of 3/8-in.-thick acrylic and does double duty. Although it’s a bit big and clumsy, I can use it as a handheld router. Or I can screw it to a pair of sawhorses, attach a primitive fence, and use it as a portable job-site router table.
Plane a straight edge
Photo 1: Use a straight guide
Run a pattern bit along a guide to cut a straight edge. For thick boards, remove the guide after the first pass.
When you have a crooked board, the best tool for creating a straight, smooth edge is a “jointer.” When you want to shave down a door just a little—more than a sander can handle, but not enough for a saw—a handheld power planer is best.
If you don’t have these tools, try the second-best solution for either of these jobs: a router with a “pattern” bit (a straight bit guided by a bearing). Just clamp or screw a straight guide to the workpiece. The router’s bearing rolls along the guide, and the bit cuts a straight, smooth edge. Use plywood, MDF or a perfectly straight board as your guide. Inspect the edge of the guide before you rout; any bump or crater in the guide will transfer to the workpiece. If you’re shaving off more than 1/8 in. of wood, make multiple passes no more than 1/4 in. deep. Choose a pattern bit that’s at least 1/2 in. in diameter. The larger the diameter, the less risk there is of chipped, splintered cuts. “Top bearing” bits are more versatile than versions that have a bearing below the cutter.
Flatten a bowed surface
Plane boards or panels flat with a straight bit. To keep the cutting depth uniform, screw your router base to stretchers that ride on rails. Hold the workpiece with blocks.
Whether it’s a cupped board or a panel that was misaligned during glue-up, the best way to flatten wood is to run it through a planer. But even if you have a planer, you’ve probably encountered situations where it’s not wide enough to handle the job. Here’s how you can use your router with a straight bit to plane wide material: Mount an oversized base plate on your router and screw the base plate to a pair of stiff, straight “stretchers.” Make your stretchers at least twice as long as the width of the workpiece, plus 8 in. Make a pair of rails at least 8 in. longer than the workpiece. The height of your rails depends on the length of your router bit. Plane the “crowned” side of the workpiece first. To do this, slide the stretchers back and forth across the rails. This is a slow process; you may have to make several passes, lowering the bit about 1/8 in. after each pass. When the crowned side is flat, flip the workpiece over and flatten the “dished” side. Routers leave a rough surface, so both sides will need sanding.
Smooth cuts on complex shapes
Create a smooth pattern from 1/2-in. MDF. Clamp or screw the pattern to a rough-cut workpiece and cut the final smooth shape with a pattern bit.
Cutting shapes with a pattern bit has two advantages over cutting with a jigsaw, band saw or scroll saw: Because you perfect the pattern first, you won’t make mistakes when you cut the workpiece. And when you’re making several identical parts, a pattern saves time, since you do the fussy shaping work only once.
To make the bracket pattern shown here, we cut 1/2-in. MDF with a jigsaw and perfected the shape with a belt sander. We traced the pattern onto boards and rough-cut each bracket, leaving about 1/8 in. excess to be removed by the router. We made the pattern and each rough bracket about an inch too long so we could drive screws through them rather than use clamps, which often get in the way of the router. The screw holes were cut off when we cut the brackets to their final length. As with straight-guide cuts, you may have to make several shallow passes and then a final pass after you remove the pattern.
Mill trim in a pinch
Make your own trim
Duplicate thin trim by first routing the profile on a wide board. Then sand the profile smooth and cut off the finished piece with a table saw.
If you need to replace a piece of trim but can’t find a match for the wood species or profile at a home center, walk over to the tool aisle and check out the router bits. Sometimes a router bit—or a combination of two bits—can reproduce a trim profile. Rounded edges and coves are the easiest to match. A 1/2-in. round-over bit, for example, produces perfect base shoe molding.
Finding the right router bit
Most home centers and hardware stores carry only common bits. For slot cutters or pattern bits, visit a supplier that caters to woodworkers. To buy online, type ìrouter bitsî into any search engine and you’ll find dozens of sources.
Many bits are available with either 1/4-in. or 1/2-in. shanks. If your router takes both shank sizes, go with the beefier 1/2-in. bit. It’s not much more expensive, and because it’s a thicker, stronger bit (more than four times the mass of a 1/4-in. bit), it will be less prone to breaking, wobbling or vibrating. A more solid bit means a cleaner cut. And the additional mass will also do a better job of dissipating heat and lessen the chance of burning a profile.
If you have a 1/4-in. router that doesn’t come with an optional 1/2-in. collet (the part that receives the bit), you may be tempted to buy an adapter so it can take a bigger bit. Don’t. It doesn’t have the same power and torque to run 1/2-in. bits. Save your 1/4-in. router for light stuff such as profiling edges and laminate work. Buy a router designed to accept 1/2-in. bits for heavier work.
Repair and reinforce cracks
When a table top or chair seat splits, you might be able glue the crack back together. But often the crack is too dirty and splintered to form a strong glue joint. And even with a good glue joint, the stresses that caused the split in the first place may crack it open again.
Here’s how to make a stronger repair: Cut a recess in the back side of the wood with a 1/2- or 3/4-in. straight bit and glue in a plywood “scab.” Make the recess deep enough to accept plywood that’s about half the thickness of the wooden part. When cutting the recess, start at the crack and work outward, gradually enlarging the recess. If you have to deepen the recess with a second pass, you may have to make a homemade base plate large enough to span the recess.
Cut perfect arcs and circles
Connect your router to a trammel and screw the trammel to a block. Cut the arc by making repeated shallow passes with a straight or spiral bit.
Often, you can create a curve that’s “good enough” using a jigsaw followed by a belt sander. But when an arc or a circle has to be flawless, a router is the perfect tool. Some careful setup is required, but the results are worth it. Mount an oversized base plate on your router so you can screw it to a 1×4 trammel. Before you start cutting the arc, raise the bit just above the wood. Then position it at the top of the arc and at both ends to make sure the cutting path is correct. When you cut, make shallow passes no more than 1/4 in. deep. Keep the router moving to avoid burn marks. You can use a 1/2-in. or smaller straight bit or a spiral bit to cut arcs. Spiral bits cut faster with less chipping, but they cost about twice as much as standard straight bits. Don’t use a spiral bit that’s smaller than 3/8 in. diameter. Small spiral bits break easily when you’re making deep cuts.
Ease sharp edges with a round-over bit
Round sharp wood edges with a small round-over bit. Run a 1/8-in. round-over bit along door bottoms to prevent splinters and snags on carpet.
Whether you’re building furniture or installing trim, avoid leaving sharp edges on wood. They’re more likely to chip, splinter or dent with everyday use. Sharp edges also create weak spots in paint and other finishes, leading to cracking and peeling, especially outdoors. Fussy carpenters often ease sharp edges with sandpaper or a file. But a 1/16- or 1/8-in. round-over bit does the job more consistently and neatly. These small-profile bits are difficult to set at the correct cutting depth, so always test the cut on scrap wood first.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- 4-in-1 screwdriver
- Cordless drill
- Safety glasses
- Table saw
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 1 x 4 for trammel
- 1/4-in. acrylic
- 3/8-in. acrylic
- Straight pieces of wood for jigs