This gretsch was in the shop for a setup and small finish chip repair, but no mention was made of the damaged jack area! With a show the same day, an extensive woodworking repair wasn’t an option.
The thin hollowbody side was crushed, with chips of wood missing, and the old jack holding on by wood fibers that wanted to give way, causing a bigger problem.
The solution: pull together as much of the old wood as possible and reinforce with an external jack plate.
First I made a small caul lined with waxed paper and drilled to fit a piece of threaded rod.feeding the rod through the jack hole I attached the caul on the inside of the cavity.I tested the caul and could see that the fibers that had been pushed into the guitar pulled mostly back into place.
From the outside I added a large washer over waxed paper and another padded caul, essentially threading a spool clamp into the guitar.I waxed the threaded rod to prevent glue from sticking to it, then saturated the break area with medium ca glue, and tightened the clamp. with the rod holding space for the jack, the glue could bond the remaining wood while filling the gaps left by the missing pieces.
After letting the glue set for an hour, I removed the clamps and cleaned up the area, first level sanding the excess glue with 360, then wet sanding through the grits to 1200 and bringing a gloss finish back using micro mesh and novus polish.
Minus a little of the opaque black, the repair looked solid, but the side is still thin and prone to re break in the same area. A black plastic jack plate was added for reinforcement, and the cheap chinese jack replaced with a long threaded switchcraft jack.
In the end, the new jack is an upgrade, the guitar is stronger than before, and with a nice setup, will be back on stage, good as new!