Shop-Made Router Jig for Cutting Flutes, Grooves & Mortises
Control is one of the keys to getting accurate results with a handheld router. Whether you're cutting decorative flutes, routing grooves, or making mortises, keeping the router moving in a straight line can be a challenge.
While building a Tower Bookcase, I needed a reliable way to rout long, straight flutes in a series of columns. Rather than struggle with a straightedge and multiple setups, I built a simple adjustable router jig that guides the router along the workpiece.
The jig worked so well for fluting that I started using it for other routing tasks, including grooves, dadoes, and mortises.
Best of all, it's made from a few pieces of plywood and hardboard, along with some basic hardware.
How This Adjustable Router Jig Works
The secret to this jig is its pair of sliding fences.
Unlike a conventional router edge guide that references only one side of a workpiece, this jig uses two fences that register against opposite edges.
This keeps the router aligned as it travels along the board.
The fences can be repositioned to accommodate different workpiece widths, making the jig useful for everything from narrow columns to wider boards.
Once the fences are adjusted and locked in place, the router follows a straight path without wandering from side to side.
That makes it particularly handy for routing long decorative flutes, where even a small deviation would be noticeable.
The same setup can also be used for cutting grooves, dadoes, and mortises, provided the workpiece offers suitable edges for the fences to register against.
Build the Router Jig from Baltic Birch Plywood
The jig consists of three main plywood components: a base and two adjustable fences.
I used 1/2" Baltic birch plywood because it's stable, strong, and well suited for shop-made jigs.
The fences ride on hardboard runners and are secured with bolts, washers, and knobs.
Cut the Base and Fence Components
Start with an extra-long plywood blank cut to the required width.
Before separating the components, cut the grooves that will receive the hardboard runners.
Making these grooves while the blank is still one piece helps keep the layout and machining consistent.
Then cut the two fences free from the blank.
The remaining piece forms the jig's base.
Drill the Router Mounting Holes
The router mounts directly to the plywood base.
Remove the router's existing baseplate and use it as a template to mark the mounting screw locations and the opening for the router bit.
Drill and countersink the mounting holes as needed so the fasteners sit flush with the underside of the jig.
Then cut the opening for the router bit.
Check that the opening provides adequate clearance for the bits you plan to use.
Before mounting the router, verify that the screws are the correct length and won't interfere with the router's internal components.
Rout the Fence Adjustment Slots
The next step is to cut the slots that allow the fences to slide across the base.
I used a router table to make these slots.
The slots work with the fence bolts and knobs, allowing you to reposition the fences and lock them securely against the workpiece.
I also drew a centerline across the top face and both edges of the jig.
These reference marks make it easier to align the router bit with layout lines when setting up a cut.
Make the Adjustable Router Fences
The two sliding fences are what make this jig so versatile.
Each fence has a hardboard runner glued into a groove.
These runners guide the fences as they slide across the plywood base.
A bolt, washer, and knob secure each fence in position.
The three counterbored holes in the fence arrangement provide adjustment for a wide range of workpiece widths.
After assembling the fences, I applied a little paste wax to the sliding surfaces.
This helps the fences move smoothly during adjustment without binding.
Before using the jig, check that both fences move freely and lock securely.
You want the jig to slide smoothly along the workpiece without allowing the router to shift sideways.
Using the Router Jig to Cut Straight Flutes
Decorative fluting is where this jig really shines.
Long, evenly spaced flutes can add a traditional detail to columns, pilasters, and furniture components.
But keeping a handheld router on a perfectly straight path can be difficult without a reliable guide.
With this jig, the process is straightforward.
First, mark the flute locations on the workpiece.
Then position the jig so the router bit aligns with the first layout line.
Adjust the sliding fences until they register against the edges of the board, then tighten the knobs.
With the workpiece securely clamped, you can guide the router along its length while the fences maintain alignment.
For deeper flutes, make several shallow passes rather than attempting to remove all the material at once.
If you're cutting multiple flutes, reposition the jig for each layout line and repeat the process.
The result is a series of straight, consistent flutes without the need to set up a separate guide for every cut.
Use the Same Jig for Grooves, Dadoes & Mortises
Although I originally built this jig for decorative fluting, it quickly proved useful for other routing operations.
Routing Straight Grooves
Grooves are one of the most common joints in cabinetmaking and furniture construction.
With the router jig adjusted to fit the workpiece, you can guide the bit along a straight path to create grooves for panels, dividers, and other components.
The two fences help maintain alignment throughout the cut.
Cutting Dadoes
The jig can also help guide a handheld router when cutting dadoes across a workpiece.
As with grooves, the important part is keeping the router aligned with the layout marks and securely supported during the cut.
For through dadoes, use a sacrificial backer when appropriate to reduce tearout where the bit exits the workpiece.
Routing Mortises
Mortises are another useful application for this jig.
With the fences adjusted to center the bit on the workpiece, the router can be guided along a straight path to remove the mortise waste.
Mark the ends of the mortise and use controlled, shallow passes to reach the desired depth.
For repeatable mortises, additional stops can help establish the start and end of the cut.
The jig provides lateral guidance, but you'll still need to control the length and depth of the mortise carefully.
A Simple Router Jig with Plenty of Uses
Some shop-made jigs are designed to perform one specific task. Others earn a permanent place in the shop because they can handle several different jobs.
This adjustable router jig falls into the second category.
It started as a solution for routing decorative flutes in a Tower Bookcase, but its sliding fences make it equally useful for grooves, dadoes, and mortises.
With a little plywood, hardboard, and common hardware, you can build a router accessory that improves control and makes accurate routing easier.
And once you have it in your shop, you'll probably find a few more uses for it.
Learn More Woodworking Joinery Techniques
A good router jig is just one way to improve your woodworking joints. From cutting grooves and dadoes to making mortises, tenons, and other traditional joints, the right techniques make a big difference.
Explore our Joinery collection for practical woodworking tips, techniques, and shop-made solutions to help you build stronger, more accurate projects.
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