Does anyone know how to mount a DW660 to the C-beam gantry plate with out having to take it apart every time I want to switch out the spindle? Because of the hole spacing, every mount I've found is designed for the Shapeoko or X-carve and requires the mounting screws inserted from the back. Even the one recommended in the forums from Inventables is a Shapeoko mount. I would prefer a solution I can 3D print.
I assume you are referring to the Inventables mount. This mount is easily adapted to V-slot by either drilling holes top to bottom 60mm apart about 10mm from the rear edge of the mount and mounting with corner connectors above and below like you would with the OpenBuilds router mount or by using a transition plate. A transition plate need be nothing more than a 1/4" aluminum plate 60mm high x 80mm wide with a couple recessed holes drilled from the back side for screws mounted into the mount holes and two rows of holes 10mm from the top and bottom edges with a 60mm horizontal spacing for attachment to the V-slot.
