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From a six metre steel rod heated up to 1200°C to an elegant and precise golf club ground by eye and hand, our forging process guarantees that the metals natural grain is preserved in every step of the process.


The Grain Flow Forging process was patented in 1998 – to create a precise iron head through multiple forging stages from a single billet of steel. Begin exploring what makes Grain Flow Forging a unique process…

What is grain flow forged


  • Grain Flow Forging allows for a highly precise iron head to be crafted through multiple forging stages from a single billet of steel.
  • The method uses the metal's natural grain to enhance the head's integrity, consistency and durability.
  • Mizuno is the only company to arrange and control this flow to pass on a performance benefit to the golfer.


Cast Head

Cast or ‘form forged’ head with loss of internal grain structure

Forged Head

Mizuno Grain Flow Forged with tight, reinforced grain structure.


One piece Grain Flow Forging
Neck and head are forged from the same single billet of steel, ensuring continuous grain through the head.

Competitor forged iron with welded neck
Unlike a Mizuno Grain Flow Forged iron the iron is made with two parts – with no continuous grain through the head.

Sound Test

Watch the video to hear the difference between cast and forged club heads


Crucial to the calibre and feedback of Mizuno clubs is the quality of materials selected for their forging…

Dedicated research into continuously improving our golf clubs led to our progression from 1025 Mild Carbon Steel to 1025E Pure Select, Boron infused steel and Chromoly Forged.


The steel behind Mizuno's softest feeling irons. Used in our one piece irons for higher level players seeking the ultimate in precision and feedback. 1025 is used for its balance of strength, bend‐ability and feel. The evolution to 1025E reduces unnecessary elements that occur during the forging process – phosphorus and sulphur.

Boron Infused Steel

Introduced in 2014 to combine the precision of a forged iron with the ball speed of a distance iron. Widely used in other industries, the smallest trace of boron to the steel mix increases its strength during manufacture, allowing Mizuno to create more complex one piece Grain Flow Forged irons.

Chromoly Forged

Initially applied in Mizuno's high ball speed Hot Metal irons ‐ Chromoly made the cross over to a Mizuno's forgings with staggering results in the JPX919 Forged. Allowing even more complex face geometry and Mizuno's first forged distance iron.


In 1968, Mizuno moved the production of its forged irons to the Chuo plant in Hiroshima – on the west coast of Japan.

Still made in the same exclusive plant today, the partnership has allowed Mizuno to evolve and perfect its forging expertise over many years.

Please tour our forging factory and follow the complete process of manufacturing a Grain Flow Forged iron.

Step 1

Uncut Japanese steel rods are delivered into the forging plant – ready to be sheared into single 10 inch billets for every Grain Flow Forged iron.

The six‐metre steel rod are sheared into 10in length.

Billets traveling down a chute.
Dirty billets in a container.

The raw steel rods are abrasion cleaned of any surface weathering prior to heating.

Clean billets in a container.

Buffered billets are ready for heating and bending process.

Step 2

Each Billet gets heated to 1200°C before being stretched and bent to the angle that will roughly form the head and hosel.

The bending stage ensures that the hosel and clubhead are forged from a single billet – to ensure a perfect grain flow throughout.

Step 3

primary forging stage

The bent billet is placed onto a forging mould and hit four times by a 1,000‐ton hammer press to tightly align grains in the metal.

To control the thickness and weight of each clubhead, the hammer operator uses a foot pedal – the process requires Chuo's most experienced staff.

The operators will work for 3 years before allowed onto the Mizuno hammers. Once on the hammers, they work 5 more years under the watch of a master operator until they can work alone.

Every head in each model (both A and B headweights) has its own forging master mould for that specific set of clubs.

Heads immediately after primary forging riding the conveyor during cool down.

Step 4


Cookie cutter roughly trims off the excess metal from the cooled heads, known as the flash…

…before being reheated for the precision forging stage.

Step 5

Precision Forging Stage

Each clubhead is reheated and pressure squeezed to create precise head shape before trimming.

With each stage of precision forging the billet is looking more and more like a useable golf club.

30 pairs of hands and eyes ensure each forged irons quality.

Until ready for grinding and plating.

Step 6


Final Grain Flow Forged head ready for stamping, polishing, plating and assembly.


After plating the finished clubs are then shipped to their assembly plants ready to be custom assembled.

The finished MP18 club

With industry-leading R&D, cutting‐edge technology and precise manufacturing, Mizuno supplies the same iron heads to its professional golf tour workshops and custom assembly lines. A PGA Tour professional and local amateur could be playing iron heads from the same production run.
We call this 'Tour Ready.'