A recent dispute in the woodworking world centered on a jig that turns a handheld floating tenon cutter into a table-mounted station. The tool maker and an independent designer disagreed publicly about who originated the idea, and the argument produced a useful side effect: it forced a close look at what actually makes mortise and tenon joinery accurate. This article treats the dispute as background and focuses on the techniques, because the same principles apply whether you cut joints with a chisel, a router, a benchtop mortiser, or a floating tenon machine.
The name of the tool brand in the original story has nothing to do with birds. If you arrived here looking for help with woodpecker damage to siding or trim, that problem is covered separately in our guide to preventing woodpeckers from damaging houses, which covers deterrents and repair options.
Mortise and Tenon Joinery Basics
A mortise and tenon joint connects two pieces of wood with a projecting tongue, the tenon, that fits into a matching slot, the mortise. In traditional work the tenon is cut on the end of one piece and the mortise is chopped into the face or edge of the other. The joint is strong because the tenon carries load across a large glued surface and the shoulders transfer compression directly. Framed doors, table legs, window sashes, and heavy shelving all rely on the same geometry.
A floating tenon, also called a loose tenon, works the same way, but the tenon is a separate piece. You cut a mortise in both parts and glue one tenon into the pair. Floating tenons have practical advantages: both mortises can be cut with the same setup, the tenon grain can run in the optimal direction, and a damaged tenon is replaced without remaking the whole rail. Production shops favor the method because it turns a difficult joint into a repeatable machine operation.
When to choose which: for furniture and cabinetry, either method works; for doors and window frames that carry weight and see movement, traditional through-tenons with wedges add mechanical strength; for production runs, floating tenons win on speed and consistency. The choice is driven by the joint’s job, the wood, and the equipment on hand.
Evaluating Jig Designs and Performance Claims
The dispute that inspired this article is instructive for another reason: it shows how much of the value in a jig lives in the workflow, not the hardware. The independent designer argued that his contribution was not the table itself but a fast, repeatable way to flip the fence so the two mating mortises align precisely, and a method for handling stock of different thicknesses. The tool maker responded that similar designs existed nearly two decades earlier, and that its product added features the earlier designs lacked, such as height adjustment.
For a buyer, the lesson is to evaluate the operation, not the origin story. A jig earns its price through setup speed, repeatability, and the accuracy it holds across a run of parts. Ask how it locates the work, how it sets depth, how it handles offcuts and different thicknesses, and whether the setup survives repeated use. The answers tell you more than the marketing ever will.
Construction is full of similar debates over performance claims, and the same skepticism applies. The discussion of R-values controversy and performance values in insulation, for example, shows how much disagreement can surround a single published number. Apply the same discipline, check the method behind the claim, when a jig maker promises accuracy to a fraction of a millimeter.
Workholding and Setup for Accurate Mortises
Accuracy in mortise and tenon work is mostly setup. A mortise that is straight and square to the reference face will align with its mating part; one that wanders produces a joint that racks or needs shims. The common failure is not the cutting tool but the workholding: if the workpiece moves between cuts, every measurement is wasted.
Setting up for repeatability
- Choose a reference face on each workpiece and mark it; every setup references that face.
- Set the fence so the mortise is located from the reference face, and lock it firmly.
- Set the depth stop and cut a test mortise in scrap of the same thickness.
- Fit the test tenon and check the alignment with a square before cutting the real parts.
- Re-check the setup after every blade or bit change.
The fence-flip method used in floating tenon work deserves attention because it solves a real problem. When you cut the mortise in the first piece with the fence in one position and the second piece with the fence flipped, both mortises land the same distance from the reference face, so the joint centers correctly in the thickness of the stock. The same trick applies whether you use a purpose-built jig or a router with an edge guide.
Handling different thicknesses
Stock rarely comes in one thickness. A jig that cannot adjust for 1/2-inch, 3/4-inch, and 1-inch material forces you to shim the work or accept joints that are not centered. Adjustable-height tables, removable spacers, or a fence that indexes off the table surface rather than the base solve the problem. Whatever the mechanism, test it: cut joints in all the thicknesses you actually use before you commit to a setup.
Mortise Dimensions and Sizing Rules
Sizing the joint correctly is as important as cutting it accurately. A tenon that is too thick splits the stock; one that is too thin leaves a weak glue line. The proportions below are traditional starting points that work for most furniture and framing applications. Adjust them for the wood species and for the load the joint will carry.
| Stock thickness | Tenon thickness | Tenon length | Mortise depth |
|---|---|---|---|
| 3/4 inch | 1/4 inch | 1-1/2 to 2 inches | 1-1/2 to 2 inches |
| 1 inch | about 5/16 inch | 2 inches | 2 inches |
| 1-1/2 inches | 1/2 inch | 2-1/2 to 3 inches | 2-1/2 to 3 inches |
| 2 inches | 5/8 to 3/4 inch | 3 to 4 inches | 3 to 4 inches |
Three rules cover most situations:
- Tenon thickness should be about one third of the stock thickness.
- Tenon length should be at least five times the tenon thickness, up to about half the width of the rail.
- Mortise depth should match tenon length, with a little room for glue and for the tenon to seat fully.
Production Workflow for Repeated Joinery
When a project needs a dozen identical joints, the workflow matters more than the individual cut. Batch the operations: cut all the rails to length first, then cut all the tenons, then all the mortises, then dry-fit the whole assembly before gluing anything.
- Cut a sample joint first and keep it as a reference for the run.
- Mark each piece with its position in the assembly; joints cut at slightly different times can drift.
- Dry-fit every joint before glue-up; a tight joint that will not close fully is easier to fix before adhesive is involved.
- Clean the dust out of the mortises before assembly so the glue does not push a plug of sawdust to the bottom.
- Clamp across the joint line, not just around the assembly, to close the joint evenly.
Time spent on layout pays back at the clamps. Numbering parts, keeping the reference faces consistent, and writing the sizes on a wall chart are the difference between an afternoon of assembly and a day of fighting misfits.
Production joinery also rewards a fixed order of operations. Measure and mark from the same reference face every time, cut all identical parts in one setup, and resist the urge to adjust the fence between pieces. Each adjustment introduces a new chance for error, and the parts that drift are the ones you will not notice until assembly.
Choosing the Right Approach for Your Shop
The right tool for mortise and tenon work depends on volume and accuracy needs. A chisel and mallet handle a handful of joints with almost no equipment cost. A router with a straight bit and an edge guide speeds up simple mortises. A benchtop mortiser or a floating tenon machine shines when a project repeats the same joint many times, because the setup time is amortized across every cut.
Budget is a factor, but so is the cost of errors. A misaligned joint on a production run can waste an entire component, which is worth more than the price difference between a simple jig and a purpose-built machine. Buy the setup that matches the volume you actually produce, not the one that looks most impressive in the catalogue. A simple jig used correctly beats an expensive machine set up poorly, and that is true at every price point.
Whatever the method, the discipline is the same: reference faces, repeatable setup, test cuts, and dry-fit before glue. A jig is only as accurate as the workflow around it, and the workflow is what separates joints that fit from joints that fight you at assembly.