The Miura forging process is unmatched, producing premium golf clubs that are in a league of their own.
Miura uses raw material called S20C, which is also referred to as premium soft carbon steel. This premium steel is delivered to the Miura factory in various girths and lengths from which billets of steel are measured and cut to correspond with the desired weight of the individual models. Achieving the highest tolerances in the industry starts here.
Once prepared to the desired length and thickness, the billets are heated to 1200°C. The first strike compresses the billet into a flat shape which allows the raw material to be placed easily into a die. The proprietary Miura process forges the club head without a hosel attached. This technique allows the Miura craftsmen to manipulate the grain structure and create the renowned Miura look and feel.
Within seconds of the first strike, the heated steel is placed into a second die where the subsequent strike forges the steel into the golf head.
The innovation of the deburring technique is what separates Miura from its competition. Following the second strike, the club head is placed in a tray where it cools before beginning its journey to the next stage. Heating the club head once while delivering the first two strikes significantly improves the precision of the forging process.
During this stage, the club head is reheated to a temperature of 800-900°C. By allowing it to cool and then be reheated, the shape of the head is maintained while still allowing the grain structure to be manipulated. This is an additional and time-consuming step but is responsible for what Miura refers to as W.D.D. Accurate Forged. During this step the weight, distribution, and density of the club head are defined.
In order to reach this stage, the Miura factory has produced three individual sets of dies for each model and loft. Dies alone will not deliver a quality iron—each model needs a precise amount of heat and force. Forging also requires the skill, patience, and experience of a Miura craftsman.
Stamping an iron includes marking the Miura logo, numbers, and scoring lines. A variety of proprietary machines and techniques are used to perform the steps without compromising the club head’s integrity.
The most critical part of this process is the stamping of grooves and scoring lines. Due to the golf industry’s dimensional standards, the Miura craftsmen must be precise. Additionally, the scoring lines become the foundations for the lie, loft, and offset of each iron. If the scoring lines are imperfect, they affect the club head’s integrity.
Pressing is the most characteristic aspect of the Miura forging process. Constructed separately, the head and hosel are attached using a proprietary spin forged technique. The friction between the head and the hosel melds the two components and creates precise lies, lofts, and offsets. During this stage, the club head will take shape and the weight tolerance of =/- .5 g will be maintained throughout the remainder of the process.
Miura-san believed the manufacturing process of forging irons was fundamentally flawed. He felt the traditional way of forging irons, with the hosel attached, meant that the hosel had to be protected from damage throughout the process. The precise amount of heat and pressure needed to create the tightest tolerances had to be compromised, which did not allow the grain structure within the club head to be properly refined.
In order to manipulate the grain structure without damaging the hosel, Miura-san decided to separate the manufacturing of both components. Additionally, he created a hosel that was CNC milled, and would therefore be perfect. With each hosel manufactured to the tightest tolerances, they would enable a shaft to be installed perfectly—centered and to the perfect depth. With a club head and hosel made from the same soft carbon steel, the result of the spin forge technique is a forged club head manufactured to the industry’s highest standards.