Find a Chicago Cutlery cleaver.
The kind with a hole in the blade.
(It's for hangin' it on a nail

)
They have a VERY heavy spine.
(At least ours does)
Corningware/Revere outlets and Kitchen Collection
carry them in our area.
I've seen them as low as $9.99!
Quite a piece of steel for the money.
Make a ring with a damp towel.
Put the squash in the ring.
Place the business end of the cleaver
against the squash and smack it with
a 16 oz. rubber mallet.
Works great for Acorn, Butternut (our fav!) and other
hard skinned veggies.
The spine works like a charm for cracking open coconuts!