> I think the term "stamping" in the UK is the same as "forging"
> in the US. The Brits refer to "pressing" but we call it
> "stamping".
>
> Greg Wolf
In addition to British cars, I have a penchant for collecting vintage
engineering text books, as I feel they more clearly define a concept than
modern text books do (modern books get off track because of all the
technology now involved in what amounts to a very basic process). So I hope
what I write will clear this up, as it is mostly a technique difference in
two forging processes that gave way to the names we are having trouble
understanding. From a 1960s (best guess, no copyright) era textbook on
material science and manufacturing methods:
"More important is closed-die forging (Fig. 4), very widely used for mass
production in industry, in which the metal blank is shaped by pressing
between a pair of forging dies. The upper die is usually attached to the
ram of a forging press or a forging hammer while the lower die is
stationary. Together they form a closed die. Closed-die forging can
produce components of greater complexity and accuracy, with a better surface
finish, than the more traditional methods not using closed dies. The dies
are made of special heat-resistant and wear-resistant tool steels. A piece
of hot metal sufficient to slightly overfill the die shape is placed in the
bottom die, and the top die is forced against it, so that the metal takes
the internal shape of the die. In hammer forging, several blows are struck
in quick succession, forcing the metal evenly into the die impressions. The
surplus metal forms a "flash" at the meeting surface of the upper and lower
dies. This is subsequently trimmed off by special tools fixed in a press,
the forging being forced through a hollow tool which cuts off the flash.
Closed-die forging is used for the rapid production of large numbers of
fairly small parts and also for very large components. For the latter-e.g.,
modern jet-aircraft components (including complete wing and airframe
units)-giant hydraulically operated presses are used, which can develop
forces of 50,000 tons and more. Such presses are highly complex pieces of
machinery, equipped with elaborate electronic and other controlling and
monitoring instruments. Forgings produced in closed dies are known as "drop
forgings" or "stampings." For some purposes the forging operation is
performed in two stages, the blanks first being treated in preliminary
shaping dies and then formed in final shaping dies.
Here is a link to Fig 4, cited in the text, for a visual of the basic
procedure:
http://astro.temple.edu/~kmr/images/stamping.jpg
HTH,
Kai
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