Thank you all for your replies - it seems I was right to be concerned.
Lead is added to encourage the chips to break off, rather than form a
big spinning ribbon of razor wire. This is what is meant by free
machining. It is important for high speed automatic operations, not
for what you're doing. After all, there are plenty of alloys and
applications where lead can't be used, but machining is done anyway.
You might want to experiment with different materials, for they well
have different machining characteristics important to you. BTW, alloys
have specifications that account for likely sources of scrap, so many
may have significant allowances for lead.
Ouch! It seems that even 'lead free' cz108 can have up to 0.3% Pb. It took
a bit of searching to find this - most of the specs imply that there is no
lead in it, or just a trace. I guess the ultimate question is, 'at what
point do I stop worrying?'
I don't know, but perhaps
there are some that are considered food grade and some that are not.
I think I'm going to have to talk to the metal dealers over this one. I
hope they have more information than they put on the web.
Thanks again,
Kit
Curt Austin (ex-metallurgist)
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