On Wed, 5 May 2021 14:33:26 +0100, newshound
wrote:

snip

Maybe they have gone the other way then, making them too hard or
hardening them throughout, rather than case hardening them?


They won't be case-hardened: inappropriate for mass produced and "thin"
components like this.

Ok.

They may be through hardened or, perhaps more
likely, have the teeth induction hardened. That will, potentially, leave
the tooth side harder and more prone to cracking than the back.

Ah, so I was closer on that then. ;-)

I'm sure they come from China, India, or Korea or some other low labour
cost region.

Not much in the way of cheap tools doesn't these days. ;-(

Low quality carbon steel is not significantly more
expensive to produce than mild steel.

Ok.

Cheers, T i m