My mallet head slips

a little beeswax to glue the head to the shaft should help

Umm a spot of glue on one surface.

You shouldn't need a wedge. The wedging action of the tapered shaft in the tapered mortice should be sufficient.

Try driving the shaft further home with a heavy block of wood.

HTH

Frank

Try holding the narrow end and rapping the broad end of the handle firmly on a bench a few times to drive the head down onto the wedge end.

Come higher humidity, you won't have the problem

What you really want is a carver's mallet. Turn one on your lathe.

I don't know how the humidity could get any higher; it's been raining for 3 days here; hasn't seemed to affect the mallet. Anyway, I contacted Lee Valley and they are sending a replacement without hesitation (I did not ask for a replacement). Once again I can't say enough kind words about L.V. If you haven't bought anything from them before, don't hesitate to do so. (Not affiliated, just a happy customer...)

Cheers! Duke