Miura uses raw material called S25C, 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.
The Miura grinding process ensures that each club head and model is ground to perfection.
The grinding process has many stages, the first being the outline grind. Miura has developed a unique procedure that grinds each model and club head profile with precision. This process ensures there is a consistent look to each individual head which would be difficult to achieve if done by hand.
The face grind is done with a machine that adjusts the depth and grooves. During this process, the Miura craftsmen ensure the groove shape and subsequent performance specs are produced to meet the R&A and USGA requirements. For Miura wedges, the CNC milling machine is used to refine the grooves. This allows Miura wedges to produce the maximum spin permitted.
Blade and Hosel Grinding
An accurate top line is created during this step. Once the top line is complete, the grinding of the hosel follows. Since the player’s eye will move from the top line, to the hosel, and up the shaft—the grind must be precise. Each worker on the grinding line must ensure this stage is completed to perfection.
Shaping is most important step of the grinding process. It is responsible for the seamless transition from short to long irons. Each iron has its own build and there are many components that go into shaping a particular iron. Adjustments to the top line, leading edge, or toe profile can help a golfer gain confidence, but requires the grinder to make those changes without altering the club head’s performance.
Shaping is the most important step of the grinding process. It is responsible for the seamless transition from short to long irons. Each iron has its own build and there are many components that go into shaping a particular iron. Adjustments to the top line, leading edge, or toe profile can help a golfer gain confidence, but requires the grinder to make those changes without altering the club head’s performance.
An integral part of the grinding process involves ensuring the lie, loft, and offset of each club head is balanced. Although these weights are measured during the manufacturing process, confirmation at this stage allows the Miura craftsmen to complete the grinding process with confidence.
Any changes to the lie or loft will have an inevitable effect on the club head. When an adjustment will have a negative impact, additional alterations will be made.
This final step produces a smooth club head without any sharp, harsh edges.
Dynamic Barrel Polishing
Once the grinding process is complete, the club heads are placed in the dynamic barrel polishing machine with small, smooth stones. The movement and vibrations of the machine polishes the club heads to a degree that is unachievable by hand. Each club spends eight hours in the barrel in order to achieve the best result.
Using belts and brushes, the finishing polish eliminates any imperfections that remain from barrel polishing. In order to polish the club head without changing its shape, the attention and precision of a Miura craftsman is needed during this step.
Centrifuge Barrel Polishing
Similar to dynamic barrel polishing, small polished stones are used and combined with a finishing additive. The centrifugal barrel machine runs for two hours, producing a fine film that is necessary for plating and coating.
Last polishing prepares the irons to receive their finishes. Chrome, satin, and matte finishes demand different polishing preparations and are created using specific buffing wheels.
Sandblasting is used to create contrast and definition on the club head. An iron such as the CB-57 has a sandblasted inner cavity with visible contrast on the back of the club head.
The final step in the polishing process is filling the club head. This includes painting the logos, numbers, and colors on each product. Once the final check is complete, the factory ships a finished product that the Miura family can be proud of.