Dave Plowman (News) explained :
It's a bit of a fine line between blades which are hard enough for a long
life and don't break too easily. There are probably expensive ones with
different steel etc for the teeth and blade.

There are, but they tend to start to split at the teeth.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk