Somewhat embarrassingly, I believe that I was the first person to break their mallet from the first swap. I wasn't doing anything reckless, I was just tapping together some half-blind dovetails when I noticed the head begin to feel loose.
I finished what I was doing, then decided to investigate further. I wiggled the head some and then was able to pull it off.
Well crap. Unsure what to do, I use a chisel and start peeling away the glue in the mortise. I use my stationary belt sander with the belt adjusted to the edge to clean off and square up the tenon. I left it like this for a couple of weeks while I figured out a plan of attack.
A few weeks passed and I didn't come up with a plan. I asked a few of the great minds of WWT for their thoughts about how to best fix the joint. There were many suggestions, but the one that I went with was from firemedic: fox wedging
. Fox wedging involves a stopped mortise and a tenon with wedges. The wedges are pushed into place by the bottom of the mortise. This joint seemed to offer the most mechanical strength while also not changing the outward appearance of the mallet. There are downsides, though. For one, I was trying to make one joint into another kind of joint. Additionally, there is no chance to test fit a joint like this. Well, below are some pictures of my process. I cut away some of the shoulder of the top of the handle with a tenon saw to make a new, square surface for the handle to meet the base of the head and also make the tenon a little longer. The mortise was already somewhat wider on some sides at the top than at the opening. I pared away some material to make this more even on the sides that the wedges would be pushing the tenon wider. I cut and shaped two wedges from hard maple and estimated length. They may look a little on the long side for this application, but the bottom of the mortise isn't completely flat and is still deeper than the tenon. Having never cut a joint like this before, it was time to just, well, see what happens.
Well, it is together. I used some slow-set epoxy on the joint and coaxed it into place with my latest big bashing tool. I clamped it and left it for a few days. It feels solid now, but that may just be the epoxy talking and not my joint. I love the mallet and am really looking forward to using it. I still need to apply some finish to the bottom of t he head where I sanded away excess glue residue from the original glue-up before I consider this thing "done," but it is nearly there.
Thanks again to Tommie Hockett for a great looking mallet. If I didn't like the thing so much, I wouldn't have spent so much time working on it. Thanks as well to everyone who helped with ideas for re-attaching the head and reinforcing the joint.