[TheForge] Re: Air Hammers Paul

[Mike Spencer]

> 1.) What is nitride steel?

>> ams 6487 (h-11 tool steel) not that that means much

Not to me.  I once worked for Michelin in their wire rolling/drawing
mill.  They had capstan drums for one stage of the process, about 10"
in diameter and 14" long.  For reasons I can explain in boring detail
if anyone cares, they had to have perfectly uniform OD.

They were ground to tolerance using an optical comparator and then put
in a sealed oven in a pure nitrogen atmosphere and held at some fairly
high temp for many hours.  Theory was that a very thin layer of the
surface converted to iron nitride, an extremely hard substance.  Then
many miles of wire rolling across it it high speed would take much
longer to begin to score the surface and make the drum unusable and a
candidate for regrinding. (Now that I think of it, I don't know what
kind of steel the drums were made of and I forget if they ran in a
corrsive environment but I think they did so they might have been some
kind of chrome or nickel alloy.)

As an aside, some of their tech was very ingenious but some of the
machinery was unchanged from circa 1910.  And they had a pair of
braided boot lace machines fed with spools of fine wire for both braid
and core.  A 3" or 4" length of braid (with the core removed) made a
springy thing like a Chinese finger puzzle that could be used to butt
splice wire in the process of feeding the machines that made the tire
belting.  Lovely machines, works of art, clever splice.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada 
                                 
mspencer@tallships.ca            
http://home.tallships.ca/mspencer/