Rabbeted-corner joint simplifies frame construction
If you want to make a lot of picture frames fast, try this technique. With one setup you cut the corner joints and the rabbet for the picture and glass.
This joint works great for pictures up to 8×10" or so. Larger than that, because of the weight of the glass, I recommend a reinforced miter or half-lap joint instead.
Set the bit's cutting edge
Set the top of the bit’s cutting edge just below the center of a test piece that matches thte thickness of your project pieces.
Position both fence faces
Position both fence faces flush with the bit’s bearing. A steel rule run along the fence should barely graze the bearing.
Rout a rabbet
Rout a rabbet on one end of two test pieces. Use a backer board to steady the material.
Check the fit
Check the fit. If it looks like this, raise the bit in tiny increments until the faces align flush. Because you’re taking material off both pieces, raise the bit by half the amount of the offset.
Machine both ends
With the bit height adjusted precisely, machine both ends of the horizontal rails with their good faces down.
Add featherboards and rabbet the inside edges of the rails as shown, face (rabbeted) side up.
Rabbet the inside edges
Rabbet the inside edges of the vertical frame pieces (the stiles) with the good face up.
Assemble the frame
Assemble the frame by gluing the rails into the rabbets in the stiles. Use spring clamps to close the joint vertically, and bar clamps to make sure the stiles seat against the rails.