Plastic dovetail keys from Hoffman are used in miter joints and for unusual angled projects, like banister rails.
Plastic dovetail keys from Hoffman are used in miter joints and for unusual angled projects, like banister rails.

Polymer Joinery For Dovetails, Miter Joints

At the Woodworking Machinery & Supply Expo in Toronto,  Hoffmann showed its dovetail joining system. It uses a dedicated router to punch butterfly-shaped dovetail “keyway” openings; then a matching polymer dovetail key is inserted to created a strong joint, glue free. It can join wood and wood related materials like MDF, plywood, particle board, etc. Mostly used for miter joints, (applied moulding to mitered cabinet doors, base frames,  furniture components, etc.)  it also works for difficult to assemble compound miter joints, like crown moulding around the top of cabinets, or on custom store fixtures. Square or butt-joints from face-frame assembly to trim carpentry (plinth or corner block-to-casing joint).

Polymer Joinery For Dovetails, Miter JointsHoffmann says the system has found its way into all types of operations, from one-man custom woodshops to large furniture factories, shutter manufacturers, architectural millworks, even stair and boat builders.

The Hoffmann routers range from foot-powered and benchtop versions, to more automated versions. Polymer Dovetail keys are available from 0.25- to 4-inch in length, in four different widths. The standard color is medium brown but custom colors and solid hardwood keys in cherry, oak, walnut, mahogany and maple and aluminum  are sold by the linear foot, to be cut to size by the customer.  

Here's a video of the Hoffman MU2 router for placing butterfly dovetail keys.

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