Screw driven Router Table Jig With DRO for Dovetail and Box Joints
This is my shop built router jig that can accurately cut dovetail slots and pins, as well box finger joints.
The jig is shown in Fig. 1-3 and its key features include
• Box frame of ½” MDT: approximately 6” X 6” X 18” overall
• ¼” thick 6" X 6" Aluminum carriage plate
• 3/8” X 16 screw attached to carriage plate with angle brackets carriage plate
• 1/8” X 2” steel angle clamping mechanism
• V-groove bearings that support the carriage on V-rails
• 12” Digital read-out
• 1/8” X 2” guide bar with a pivot hole and three holes to align the guide bar at 90⁰ for box joints and dovetail slots, and 90⁰+8⁰ for cutting dovetail pins
The jig can cut workpieces up to 6" wide.
The box frame provides for a rigid frame for the V-rails and associated V-bearings (4 for $14 on eBay). The ½” MDF frame is assembled with ½” Al angle and machine screws; the screw holes are drilled a little oversized so the fit and alignment of the carriage plate and V-bearing can be adjusted resulting in the carriage plate being square with the bottom of the frame, and no wobble of the carriage as it moves along the rails.
The slides below show the details of the jig. In use, the DRO (Igaging, Amazon) is used to accurately position the carriage and attached workpiece according the the desired dimensions. For box joints with uniform spacings, this is pretty simple; for dovetail pins and slots, I make a diagram as shown in Figs 7 and 8. Thankfully, all you need is simple arithimetic to determine dovetail dimensions -- no need to dust off those trigonometric brain cells!