This is the most common and wide family, which can be divided in two groups: the sulphur-only steels, such as 11SMn30 and 11SMn37, characterized by good machinability, and their versions with lead, 11SMnPb30 and 11SMnPb37 with a significant increase in machinability , up to steels with tellurium and bismuth, such as 11SMnPb30+Te+Bi and 11SMnPb37+Te+Bi, which take machinability to the highest levels with the addition of cold deformability, thanks to the presence of tellurium.
For those who want highly machinable free-cutting steels but with a lead content below the limits set by the REACH regulation and the RoHS Directive, we recommend GFast30 and GFast37 steels.