Gary Beals wrote on extrusion dwell in last week's E-Sylum. There are other metalworking terms that apply to making coins andmedals. Few numismatists know of these concepts let alone the terms.

Think of a mint as a large metalworking plant. The terms of this industry are a part of coin and medal manufacture. I have included relevant metalworking terms in my Encyclopedia of Coin and Medal Technology.

Many of these terms concern dies and their use. An important part of making dies is heat treating where dies have to be hardened and softened as needed. One of these terms is normalizing, returning a die to to a normal state after some heat treating process.

As an example, a private die maker told me the story of a client who ordered a Columbus medal die. He was in a hurry to obtain the die. Over the objection of the die maker he left with die in hand. It was wintertime and the die cracked in the cold temperature. He sheepishly returned an hour later, stating the die maker was right and to order a new one. The die had not been normalized, returned to room temperature.

Another metalworking term is strain ageing, failure in a die after a period of use. No one knows in advance when a die will break. This can happen with the first blow, or two hundred years later. Although in recent times the quality of steel is much better than years ago.

This is a major reason why it is often impractical to restrike from old dies. Age often makes old dies break because of strain ageing. Yet we have Papal dies still serviceable after two hundred years. The Paris Mint wisely struck a series of old dies side-by-side obverse and reverse on a strip of tin. It displayed the image on both dies without fear of breaking.

Many instances can be recalled of old dies breaking. Bob Bashlow acquired the Confederate Cent dies, took them to August Frank in Philadelphia and ordered restrikes. Of course, they broke. August Frank had to bind the broken parts together enough to withstand the pressure of making hubs. It worked and striking dies were made from the hubs after the diecrack on the surface of the hubs were chased off.

Pressmen learn to respect the dies they work with. For instance, it was observed dies were breaking on a Monday morning more so than other days of the week. The dies strain aged in two days over a weekend where they didn't overnight. If dies are to be stored knowledgeable pressmen will perform stress relieving on the dies before they go to the die vault.

Many of these terms are concerned with the interior of the die stock, which, of course, no one can observe. The crystalline structure of the iron effects hardness, tensile strength and ductility of iron the dies are made from.

While the artist and the numismatist are concerned with the image on dies, there is considerable technology to create and use dies correctly.

To read the earlier E-Sylum article, see:
BOOK REVIEW: ENCYCLOPEDIA OF COIN AND MEDAL TECHNOLOGY (www.coinbooks.org/esylum_v19n20a05.html)