John Middendorf started developing the A5 hammer in 1986. After research, design, and experimenting to refine the design, he had Ajax Forge in Los Angeles forge 540 heads out of 4130 steel. Each head required milling the face, drilling the carabiner hole, and shaping the pick tip before the heads were sent for heat treatment. A test batch of ten heads treated yto RC42/43 proved too soft, so the production run was treated to RC45/46. Handles came from the OP Link handle company.
The A5 hammers proved popular and they sold out in a few years. John made a second batch of 250 hammers in 1996. These also sold out quickly. These were made from 4340 and were hardened to about RC48, similar to the Black Diamond investment cast hammers. Second-batch hammers are easily identified by their yellow handles.
Source: Middendorf, John, 2022. A5 hammer production forge process. Downloaded from https://www.bigwallgear.com/p/a5-hammer-production-forge-process on 2025-03-28. I recommend this article for those seeking more details than I've presented here.
 |  |
↑ 018: A5