I am making a frame for a heavy antique mirror that is 54" by 16" by 1/4" thick. Currently, I have glued up the frame. It consists of four lap jointed 2x4's.
After the glue had dried, the frame did not sit flat on the bench. When I held one corner down, the adjacent corner rose 5/8" off the bench. This indicated the frame was not square, so I investigated further with winding sticks.
The frame is indeed out of square. It is twisted. The next step in the in the build process is to use a router to cut a 1/4" rabbet that will accept the mirror. This rabbet will be cut with an upcut bit spun by a plunge router with an edge guide. Before I proceed with cutting the rabbet, should I fix the twist in the frame? I have identified several options, but as I have never dealt a work piece that is this far out of square, I am not sure what to do.
- Do nothing, force the mirror to flex to adapt to the twisted frame.
- Use a router and jointing plane to remove material until the winding stick are parallel.
- Cut the rabbet deeper in the corners that are twisted up to accommodate the mirror.
What is the best option, is there an option that I have overlooked?
I decided to proceed with this twisted work-piece. The next step was to cut a rabbet for the mirror to sit in. After cutting this rabbet, the frame was noticeably less twisted. Lots of material was removed, apparently some internal stresses in the wood were twisting the frame:
After cutting the rabbet, I gave the mirror a test fit. It looked pretty good. The mirror weights around 40 lbs, and after test fitting the mirror, I decided that the frame needed a brace. When gluing the brace, I warped the frame a little past level:
Checking again with the winding sticks, the frame looks like it's nearly perfect:
In retrospect, I definitely recommend trying to salvage a twisted glue up.