I remember a nice clear X-radiograph of a die from Coppergate, York showing where a steel face had been welded on to a hefty chunk of iron. The easiest way of working would be to anneal the steel until it became relatively soft, cut the design, then quench to achieve the required hardness. In theory it might be possible to cut the design into iron then carburize the surface and quench. This was common practise for files, but I don't know if sufficient detail would be retained for a die.
David Starley PhD
Science Officer
Royal Armouries Museum
Conservation Department
Armouries Drive
Leeds LS10 1LT
United Kingdom
Tel. 0044 (0)113 220 1919
Fax 0044 (0)113 220 1917
-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
Peter Northover
Sent: 23 September 2005 11:56
To: [log in to unmask]
Subject: Re: [ARCH-METALS] Early minting technology
I very much doubt whether any coin die was made of cast iron. Ancient
and medieval coin dies have been made both of iron/steel and bronze.
Unfortunately their rarity means and/or numsimatic importance means that
they are rarely accessible for detailed technical study.
It is generally believed that the designs on dies were engraved; this is
certainly the case with medieval wrought iron/steel dies. I have
examined long cross coins of Cnut (early 11th century) where the
engraver's setting our marks as well as the actual design have
transferred to the coin.
Occasionally the metallurgy of dies could be quite sophisticated; a
counterfeiter's coin die from Mughal India I have analysed proved to be
a martensitic high tin bronze. Even so it's hardness was nowhere near
that of modern alloy steel coin dies with Vickers hardnesses around 900
- an overaged die steel was the first time I ever encountered a Vickers
hardness over 1000.
Yours,
Peter Northover
Edgar wrote:
> Early coins of gold and silver were minted
> from cast blanks using hammer struck dies.
>
> These dies - I read - were made from iron.
> http://www.neo-tech.com/businessmen/part4.html
>
> How did the ancients manage to produce iron dies
> since they did not have the technology to produce
> cast iron?
>
> Did they cast a reverse die in bronze which could
> then be stamped onto the head of a red hot piece
> of iron?
>
>
> Edgar
>
--
Dr Peter Northover,
Materials Science-Based Archaeology Group,
Department of Materials, University of Oxford
Tel +44 (0)1865 283721; Fax +44 (0)1865 841943 Mobile +44 (0)7785 501745
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