Some strange 12L14 bar stock...

Some strange 12L14 bar stock...

Post by Spehro Pefhan » Mon, 28 Aug 2000 04:00:00



(I crossposted this to a couple more groups because it is interesting,
maybe even useful. BTW, 12L14 is a common free-machining resulfurized and
rephosporized steel alloy with some lead added to improve machinability.

Composition: Carbon: 0.15% max, Mn: 0.85~1.15%, P: 0.04~0.09% max,
S: 0.26~0.35% max, Pb: 0.15~0.35%)

Quote:
> We run 12L14 in a bar fed CNC lathe.
> Every once in a long while I get a delivery of 12L14 that has a poor
> surface finish, kind of micro pitted.  It machines and chip breaks just
> like you'd expect except for one strange thing.  The chips are hyper
> magnetic.  They stick to the cutoff tool and when the drills and taps
> pull out they look almost like magnets in iron filings.
> These magnetic chips cause a couple of problems.  First, they sometimes
> stick to the face of stock stop and cause part length variation (we
> can't face the part after feed out because it's too long and slender).
> Second, we have to clean the chips off the parts before we can do the
> second-op work on them.  And lastly, the parts don't have a very nice
> appearance where the mill finish shows.
> First time I noticed this strange happening, I thought maybe the
> machine spindle was somehow magnetizing the stock.  No, I've tried
> running a "regular" bar of 12L14 between bars of the strange stuff.
> The regular stuff performed normally, it's only the funny stuff that
> has the magnetic chips.
> My supplier, of course, says I'm the only one that's mentioned this and
> they don't see any thing wrong with the stock.  Seems like whenever I
> get this funny stuff, all the other suppliers in town have the same
> stock.  I assume they all buy from the same mills.
> Has anyone else seen this?
> Sent via Deja.com http://www.deja.com/
> Before you buy.