Mizuno JPX919 iron series finds new distance, feel and forgiveness in new metals and manufacturing

August 29, 2018

It would be easy to say the new Mizuno JPX919 series of irons are all about the metal. The company is legendary for its jewel-like and tour-proven forged irons and most recently for its uniquely hot cast game-improvement designs, always with an attention to appearance. But suggesting that its latest lineup of three new irons is just another exercise in metallurgy and manufacturing is overlooking another crucial component of the Mizuno approach, another “m” word, said the company’s David Llewellyn, director of research and development.

“At some point that cosmetic design has to meet up with the engineering design. That’s kind of where the magic really happens,” he said. Llewellyn refers to the new line as “a merging of dynamism and simplicity,” but drawings are only an inspiration, he said.

“Ultimately the goal was to meld the engineering side with the aesthetic design side.”

The company’s profile has been bolstered over the last two years with an increase in tour use, largely by players suddenly finding themselves free to choose any iron they wanted following Nike’s departure from the club business. The highest profile non-Mizuno staffer using its clubs has been Brooks Koepka, who has won three majors in the last two years using the JPX 900 Tour irons, clubs originally designed for Koepka before he signed with Nike.

With more players’ opinions to build upon, Mizuno’s team set about developing the followup not only to the 900 Tour, but also to Mizuno’s most commercially successful iron in recent memory, the JPX 900 Hot Metal. The result of those deliberations are the three new models that make up the JPX919 series. They include the pro-ready JPX919 Tour, the players-distance JPX919 Forged and the fast-faced game-improvement JPX919 Hot Metal. Each reflects a unified look with engineering efforts geared to three distinct player types that range from the elite to the mainstream.

The JPX919 Tour takes off from the 900 Tour’s foundation first by incorporating the company’s “HD grain flow forging” technique first seen in last year’s MP-18 line. That manufacturing technique uses a special frame to concentrate the flow of the 1025E carbon steel in the hitting area for a tighter grain structure to improve feel.

The JPX919 Tour is designed to produce a more forgiving forged cavity shape by selectively thinning the topline and redistributing mass toward the toe. Its structure was driven by answering familiar questions in new ways, said Chris Voshall, senior design engineer.

“Where is the weight most necessary, where would you like to have weight, where do you not need the weight, where can you move it around,” he said.

That meant a thinner topline, but one with a slight bevel and distinct draft angle so that it still stabilizes the iron’s frame. The thinner topline also allows extra weight to go towards the toe and the sole, two areas that also make the JPX919 more forgiving than a typical better players iron, even those that use multiple materials like tungsten to boost stability, or moment of inertia.

“It’s living right there with some bigger, perceived-to-be more forgiving golf clubs,” Voshall said. “The secondary benefit from more toe weight beyond increasing moment of inertia is a more centralized sweet spot.”

Next in the lineup is the latest iteration of Mizuno’s forged players distance iron. The new JPX919 Forged uses a boron-infused version of the company’s trademark 1025E carbon steel. The boron strengthens the steel, allowing for a thinner face and better weight distribution.

But that’s only half the story behind its faster performance. Hidden in the JPX919 Forged’s sole is CNC-milled cut-through slot (covered by a welded strip of steel). The slot creates more spring-like effect through a larger thin area of the face, while at the same time making room for a deeper undercut cavity. The design feature also creates a lower center of gravity to help increase launch angle. Voshall said the JPX919 Forged, which also features the “HD Grain Flow Forging” technique, was a challenging project with a special appeal.

“Using the CNC milling to go through the sole side allows us to focus more mass low and deep and at the same time this cut now runs parallel to the face so that thin area is now thinner for a longer span,” he said. “This is the golf club we’ve always said internally that if we were to make and sell only one club at Mizuno, it would be this one. This really checks every box in terms of performance, feel and look.”

Of course, the one iron that’s sold the most in Mizuno’s lineup and the one that might be most beneficial to more golfers would be the upgrade of the JPX 900 Hot Metal. Like its predecessor, the new JPX919 Hot Metal again uses Chromoly 4140M, a high-strength steel alloy that creates a thin, fast-flexing face.

“It allows us to go very thin on the face but maintain a certain amount of malleability in terms of the hosel in order to be able to do what we do best, which is custom fitting to get your appropriate lie angle,” Llewellyn said. (Toward that end, Mizuno has also updated its Shaft Optimizer fitting club. The company’s fitting software analyzes sensors in the fitting club to now not only diagnose the ideal shafts for a player in just a few swings, but also the correct lie angle, too.)

The the JPX919 Hot Metal is a complicated, one-piece casting with a 360-degree undercut. It controls sound and optimizes vibration through a series of supporting ribs within the topline without raising the iron’s sweet spot. Llewellyn said the sweet spot is about half a millimeter lower from 4-iron through 9-iron compared to the JPX 900. That allows for stronger lofts in the 4- through 7-iron, a combination that produces more velocity for a similar launch angle for more distance.

Available in stores next month, but on pre-order now, the three new JPX919 irons are offered with no upcharges for the company’s vast menu of custom steel shafts and grips. The JPX919 Tour will retail for $1,200 (3-iron through pitching wedge, eight pieces, right-hand only). The JPX919 Forged is $1,300 (4-iron through gap wedge, eight pieces), and the JPX919 Hot Metal is $1,000 (4-iron through gap wedge, optional sand and lob wedges, eight pieces).