[Illustration: LIMBER HOOKS: ILLUSTRATING DUPLEX METHOD OF DROP FORGING.]
[Illustration: TRUNNION BRACKETS FOR 6-INCH HOWITZER GUN, DROP FORGING. [_To face p. 145._]
Significant, and sufficiently expressive of appreciation, if not of actual open-mouthed astonishment, is the following letter received by Mr. Cooke from a well-known Government Department: "I have to thank you and your staff on behalf of the Ministry of Munitions for the excellent work you have done in producing stampings of trunnion brackets. The part in question has hitherto been considered almost impossible to produce as a stamping, and the work you have now produced will add materially to the efficiency of this important equipment. I should be glad if this letter could be brought to the notice of your subordinate staff who carried out the work." From the same source, but at a later date, came this further little note of esteem: "Your previous production of the trunnion bracket has been the means of great saving to the State, and it is with great satisfaction that I am able to again congratulate your operating staff on a renewed success in your stamping department."
For the benefit of those uninitiated in the fascinating art of drop-stamping or forging, it may not be considered superfluous if a brief explanation is given of the principles embodied in the system, and for this purpose one cannot do better than read and inwardly digest the opinion which has been advanced by Mr. Brett, founder of the Brett Patent Lifter Company of Coventry and inventor and patentee of the hammer in question.[8] "Having in mind," he says, "that the plastic or forgeable condition of wrought-iron or steel, when obtained, cannot be retained beyond limited periods, especially in the case of articles having thin or light parts, when its duration is very brief," it rests with the engineer "to provide for the forger a suitable form of power for actuating the dies or tools by means of which properly-formed forgings may be obtained." Further, "this power must be capable of instantaneous application," similar in all essentials to that produced by the smith "with hand hammer or sledge; that is to say, a perfectly elastic blow of sufficient force to produce an immediate and substantial effect upon the material."