Alloying Yellow brass to create free machining brass

Alloy 'regular brass' to be free cutting brass. Looks like adding 3% lead to yellow brass will do the trick. My lead is most likely the Linotype alloy 4% Tin, 12% Antimony, and 84% Lead.

LL = Pb + Sb + Sn
Lets restate this as
LL = 84% Pb + 16% other

Calculate amount of LL, Linotype Lead,that contains 1g of Pb

84/100 LL  = 1
LL = 1*(100/84)
LL = 1.19
working backwards to check
.84 * 1.19 = 0.9996

So we need to use 1.19g of printers lead to get 1 gram of lead

A 1000g batch of free cutting brass will need 30 grams of Pb.
So we use 1.19 * 30g = 35.7g of printers lead.
Combined with 1000g - 35.7g or 964.3g of yellow brass.

Found this on the addition of antimony to brass.

Arsenic and antimony can be added in small quantities, up to about 0.05 wt%, to all brass alloys containing less than 80% copper to inhibit the dezincification types of corrosion in yellow brass alloys.

Thinking is that .05 is only a limit in that
 more will not help with the dezincification.  Going to give it a try.