|Fine Woodworking (www.finewoodworking.com) reviewed the Keller 1600 and 2400 (now models 1601 and 2401). This review is © 1989 Fine Woodworking.
Keller is the only manufacturer I know that makes jigs specifically for routing through dovetails. The Keller templates, shown in the photo at right (not shown here; see Models for photos of the templates), are designed solely for through dovetails, and I found them uncomplicated and easy to use. The ruggedly constructed, ½-in.-thick, machined aluminum templates aren't inexpensive, but you may want all three models to work on a ful range of wood thicknesses.
Each model comes with two template, one for cutting pitns and the other for cutting tails, as well as router bits that have pilot bears mounted on the shanks above the cutters, eliminating the need for guide bushings. The smallest bits have ¼-in.-dia. shanks; the largest, ½-in.-dia. shanks. Each template is screwed to wooden backing blocks (not supplied), and then the workpiece is clamped to the back blocks, which prevent wood tearout as the router bit exits the cut.
Working with the templates is straightforward. The tails are cut first using the dovetail bit. Then, one or two of the tail lovations are transferred to the pin board in the same manner as if you were making hand-cut dovetails. During production runs, stop blocks can be clamped to the backing blocks to eliminate any need for transferring marks, and to make it even simpler to align th pin board to the pin template. After the pin board is clamped, the pins are cut with the straight bit. The photos on p. 47 (not shown here; see Performance for photos of the templates in operation) show the Keller model #2400 set up to cut the pins and tails. There's no restriction on the width of the wood: You just have to reposition the template and continue routing. If you're setting up the templates for the first time, cut a trial joint in scrap piece to check the fit. You can adjust the fit of the joint in either of two ways: by changing the router bit depth or adjusting the pin template location. The pin template has slots for the mounting screws to allow this adjustment.
Shortly after I evaluted these jigs, Keller introduced revised versions of its templates for both the #1600 adn #2400 models, which are now models #1601 and #2401. Keller is also supplying additional router bits with these templates, as well as for the unchanged model #3600 template, which inreases the range of wood thickness these templates can accommodate.