Over time my mallet handles appear to tighten into the head by drifting deeper into the mortise.
If the handle gets loose a drop or two of wood glue helps to hold it in.
One my latest mallet > https://sawmillcreek.org/showthread....7-Mallet-Mania < experience helped to get the mortise in the head and the handle taper fit much better than any of my other mallets including a manufactured mallet, Footprint, bought ~30 years ago.
The taper for this one is 8º, or 4º on each side. The edges cut off of the handle were used to support the head when boring the mortise on a drill press. This allowed drilling close to the corners while staying inside the layout top and bottom. A pad saw was also used to clear some of the waste:
Pad Saw.jpg
Another tool that helped at removing bumps on the end grain in the mortise was an old chisel ground to a 90º bevel. It works like a one tooth float.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)