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Trimming Tool

Trimming Tool.  A cutting tool used to remove the flash or overflow of metal from around the edge of a fully struck medal, and to give it a finished shape. A trimming tool

can be used to trim round medals (other methods are more efficient for large round medals however) and a few pieces can be cut to shape by hand (by jigsawing), but trimming tools are most useful for long runs and necessary for unusual shaped medals. A trimming tool has two parts:  a punch and a cutting plate. While the punch is similar to a blanking punch it must have a hollow area in the end to keep from mashing the relief of the medal being trimmed.

Trimming tools came into use in the medallic field with the advent of open

face dies. This allowed designers to create a wide latitude of unusual shaped medals, but required a trimming tool to be made for each new shape. The odd shapes could be struck on blanks of any size (or shape) as long as they were larger than the image size of the die. Trimming then was a final step before the item left the pressroom. The use of trimming tools became useful also for small round medals and particularly for medals with an integral loop.

The punch and cutter plate are made by tool and die makers, who must machine the two to mate perfectly. The cutter plate must be thick enough for the walls to accomplish their shearing action, and beneath that to have sloping sides for the sheared piece to exit without hanging up (see drawing). The punch is formed on the end of a rod or bar. The matched set must be suitable for mounting on a press for trimming.

How trimming is accomplished.  A punch and its matching cutter plate are mounted in a press, usually a drop hammer press. A fully struck up piece is placed in position on top of the cutter plate over its aperture; it should "seat" on the nest there (and, obviously, it is larger than the aperture so it does not fall through). The press is actuated and the punch comes down and in effect pushes the piece through the opening in the cutter plate. The piece takes the configuration of the exact shape of the aperture in the cutter plate.

The piece to be trimmed is softer than the cutter plate that is made of hardened steel. The sides of the aperture in the cutter plate is where the shearing action occurs.

The trimmed piece falls into a hopper below; the flash or skeleton of the unwanted excess metal remains on top of the cutter plate. It must be removed (by hand) before the next piece is seated in position (by hand).

As with all shearing operations in metalworking the trimmed piece may show

evidence of the shearing with striations on the edge, and also have burrs formed on the last side to pass through the aperture, said to be the burr side. All pieces must be deburred for a finished appearance but in most instances this is accomplished by a typical abrasive blasting during finish and finishing.

Design requirements for trimming.  If a medallic piece is designed in any shape other than round for a long run it must be made to accommodate the trimming tool. As such it must have a border on one side wide enough to accommodate the sides of the punch. This border can be on either side of the medal but it should be remembered that the burrs will occur on the side which comes in contact with the punch (burr

side). Some astute designers therefore place the border on the reverse to allow grater design area for the obverse.

Also the shape of the design should be such that no tiny projections are created on any side; not only would these easily break off the finished piece, it is impossible to create a cutter plate with such projections.

excerpted with permission from

An Encyclopedia of Coin and Medal Technology

For Artists, Makers, Collectors and Curators


Roger W. Burdette, Editor

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