Anyone who's spent much time in a machine shop will be familiar with the hardware commonly used for work-holding and fixtures on a machine tool. In particular, the flange nut is a common item used with strap clamps and other work-holding devices. TeCo is a well-known manufacturer of these items.
I just happened to be shopping for some of these flange nuts for a fixture and noticed that some of these are specified as being made from 12L14 (leaded steel). This detail is not buried in the data sheet, but appears where I would interpret it as a feature, meaning a purchaser might have reasons for choosing one in this material, as opposed to one in a stronger steel for example.
My question is why 12L14 might be a preferred material in this application. I've understood leaded steels to be free-machining, which would make manufacturing easier (although making the part non-weldable), but I can't imagine that would be a driving factor in high-volume parts like this and in any case wouldn't rise to the level of a feature to be advertised if that were all it was.
I have two theories:
- The lead in 12L14 somehow increases the lubricity of the fastener, making it less likely to bind (or perhaps gall) in a frequently used fastener like one in a manufacturing fixture.
- Lower tensile strength (although not that much lower) is a plus, because if over-tensioned, it's better for the fastener to give than the t-slots machined into an expensive machine table.
Can anyone enlighten me?