Tool review: Biscuit Joiners

If you're looking for a power tool that quickly and accurately joins two pieces of wood, get a biscuit joiner. Among the many joints these machines help you tackle: edge-to-edge, end-to-edge, and miter-to-miter. Biscuit joiners have been around since the late 1960s and continue to help craftsmen create strong joints held with pressed-wood biscuits and glue. We tested six popular machines, and here's what we found.

Depending on the thickness of the wood and type of joint, you can cut the slots one of two ways. Read on to learn what you need to know to be successful at either method.

— Referencing from the base. For all the biscuit joiners we tested, this method works perfectly when using ³⁄₄ "-thick stock: You just rest both the tool and board on your workbench, and the tool cuts slots centered and parallel to the base. But if you want to position a slot somewhere other than ³⁄₈ " from the face—in the center of a 1-¹⁄₂ "-thick piece, for example—you must either elevate the joiner with shims under the base or use the fence as your reference surface. (By the way, don't reference from the fence and base at the same time; it could cause misalignments.)

— Referencing from the fence. Not only is this the preferred method for stock thicker than ³⁄₄ ", it's also the only option for slotting miter joints. As important as this is, the fences proved to be the breaking point for four of the six tested models.

For example, the fences on the DeWalt DW682K and Porter-Cable 557 move up and down on a rack-and-pinion gear that makes adjustments easy and holds the fence parallel to the blade. The other joiners' fences struggled to maintain a parallel plane without further tinkering and fine-tuning, resulting in various degrees of unparallel cuts and misaligned joints.

Scales on the sides of the fences help you position them accurately; if you select 1", for example, your slot will be 1" from the top of the board. Only Triton's front-mounted fence scale proved too inaccurate to rely on [photo].

As you see in the photos below, you cut slots in mitered boards by tilting the joiner's fence to your desired setting. Porter-Cable's fence, our favorite, tilts from 0° to 135° with positive stops at 45° and 90°, as well as an easy-to-read scale. The 135° setting allows you to capture the acute angle of a mitered workpiece for a secure grip [Photo A]. Fences on the Craftsman 17539 and Ryobi JM82K also tilt to 135°, but plastic support plates restrict movement and won't work in stock less than ³⁄₄ " thick.

The Makita 3901 and Triton TC9BJM each use an included right-angle attachment [Photo B] that slides onto the fence, which tilts up to 90°. With this accessory attached and the fence tilted to 45°, you can wrap around an acute miter, but both machines proved difficult to use and damaged the fragile wood fibers at the miter's point.

With these two machines and the DeWalt (which does not tilt beyond 90°) we found it easier to cut miter slots by tilting the fences to 45° and cutting instead from the obtuse side of the miter. But to position slots nearer the heel end of the miter rather than the center—where a #20 cut will break through the opposite face—you have to attach an auxiliary fence [Photos C, D]. None of the owner's manuals for these tools mention this, however.

— Aim for snug-fitting slots. Sometimes a little looseness in the fit between slot and biscuit can help you overcome minor misalignment of mating slots as you create a joint. (The pressed-wood biscuits expand after absorbing the glue's moisture, tightening the fit.) But too often in our tests, sloppy slots led to uneven joints. We'd rather just get it right the first time with a well-machined slot, and the DeWalt and Porter-Cable best delivered these.

— Plunge with precision. All six joiners feature microadjustable stops for setting the plunge depth for the most common biscuit sizes: #0, #10, and #20. For most woodworkers, those three settings will suffice. Porter-Cable includes a setting (and special blade) for 1¹⁄₄ "-long face-frame biscuits. The other settings are geared more for the professional user than the home woodworker and accommodate 3-³⁄₈ " biscuits (for greater strength) and metal knockdown fasteners.

For this article, we reviewed the Craftsman 17539, DeWalt DW682K, Makita 3901, Porter-Cable 557, and Triton TC9BJM.

To buy a biscuit joiner you'll be able to use accurately and efficiently with little stress, you have to spend at least $200. We simply couldn't get the $100 units to perform without great frustration. (If you buy one of these, expect to do a lot more planing and sanding on the glued-up joints to get them smooth and even.)

By now you've probably figured out that two biscuit joiners stand out from this field of six: the DeWalt DW682K and Porter-Cable 557. They both make accurate cuts, and, aside from a few minor quirks that we can live with, prove easy to use. That's why they share our Top Tool honors. But if you intend to make face-frame joints or want the ease of cutting acute-angle miters, then go with the Porter-Cable.