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ELI5 - How forged irons work


TBS
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I understand, on a surface level, how woods, or GI irons work with a thinner face and a trampoline effect, but how does this work with a 1 piece forged iron?

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7 hours ago, TBS said:

I understand, on a surface level, how woods, or GI irons work with a thinner face and a trampoline effect, but how does this work with a 1 piece forged iron?

“Trampoline effect” depends on the properties of the face (metal or other), area and thickness. Many club makers offer iron sets that are forged with perimeter weighting and a thin face, e.g. a cavity back like the Mizuno JPX921 Forged, and that will provide some trampoline effect. A forged muscle back iron will have very, very little trampoline effect (essentially zero, but no metal is perfectly rigid). COR is probably the most common indicator of trampoline effect. The USGA regulates COR so there's a limit to what club manufacturers are allowed to do. Obviously the ball compresses far more than any club face.

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What he said.  I'll add that the higher the swing speed, the more relative increase in ball speed with a thin faced iron.  For someone like me with a slower swing speed, loft is by far the determining factor of ball speed and distance.  That means I get the same distance on a well struck shot with a 34 degree club whether than club is a solid body forged iron or a thin faced cast iron.  As far as the difference in a forged face and a cast face, I am convinced that the difference in feel, if any, is a product of the design of the club head, not whether it is forged or cast.  Others will disagree.

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14 of the following:

Ping G425 Max

Callaway Epic Max 5 wood

Cobra F9 Speedback 7/8 wood set at 23.5 degrees

Callaway Epic Max 11 wood

PXG 0311P Gen. 3  6-GW

PXG 0211 5-GW

PXG 0211 sand wedge bent to 53 degrees

Maltby M Series+ 54 degree

Ping Glide 3.0 Eye2 58 degree

Ping Glide 3.0 60 degree

Evnroll ER2

Ping Sigma 2 Anser

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Also, the type of club construction will have an impact on the material properties of the steel used.  In general, cast construction allows for a greater variety of material to be used opposed to say a forged club.  For example, the steel used in forged clubs might not be as strong as in a cast club simply because the stronger steel does not lend itself to the forging process.  The result is that you have to make the face thicker in the forged club than in a cast one, which would decrease that trampoline effect further. 

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5 hours ago, Hook DeLoft said:

What he said.  I'll add that the higher the swing speed, the more relative increase in ball speed with a thin faced iron.  For someone like me with a slower swing speed, loft is by far the determining factor of ball speed and distance.  That means I get the same distance on a well struck shot with a 34 degree club whether than club is a solid body forged iron or a thin faced cast iron.  As far as the difference in a forged face and a cast face, I am convinced that the difference in feel, if any, is a product of the design of the club head, not whether it is forged or cast.  Others will disagree.

I have some agreement and some disagreement.

  • Agreement: "What he said." What Middler said is spot-on!
  • Agreement: "The difference in feel, if any, is a product of the design of the club head, not whether it is forged or cast." Mostly agree. It's hard -- and expensive -- to forge a deep-cavity clubhead, so you don't see many forged clubs with thin clubfaces. There have been experiments proving that feel comes with the design, not the forming process. Where I disagree is that the softer and perhaps denser metallurgy of a forged head probably makes a different sound from a typical cast head. It has been repeatedly determined with controlled experiments that about half of what we sense as "feel" is really sound.
  • Disagreement: "The higher the swing speed, the more relative increase in ball speed with a thin faced iron." The higher the swing speed, the higher the absolute ball speed increase -- that is, the difference in yards. But the relative ball speed increase -- the difference in percent -- is just about the same. In fact, I have seen at least one analysis that shows the low-speed golfer to have ever so slightly more percent increase from a thin face.
Edited by Dave Tutelman
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2 hours ago, Dave Tutelman said:

I have some agreement and some disagreement.

  • Agreement: "The difference in feel, if any, is a product of the design of the club head, not whether it is forged or cast." Mostly agree. It's hard -- and expensive -- to forge a deep-cavity clubhead, so you don't see many forged clubs with thin clubfaces. There have been experiments proving that feel comes with the design, not the forming process. Where I disagree is that the softer and perhaps denser metallurgy of a forged head probably makes a different sound from a typical cast head. It has been repeatedly determined with controlled experiments that about half of what we sense as "feel" is really sound.

As I think you’re noting, the alloys used for most/many muscle backs can’t be used for casting club heads, and feel is in part a result of the properties of one alloy versus another. Furthermore, the forging process alters the grain structure and can “aim” or “point” it in a particular direction creating a directionally strong component. Forged parts are anisotropic (contains different property-measurement values in different directions) while castings are isotropic (contains similar property-measurement values in all directions). Forgings generally have higher mechanical properties and better ductility (depending on alloy). Through dramatically improved now vs early cast clubs, cast clubs have more porosity, shrinkage, cavities, and cold pour issues.

Forging is more expensive than casting. If there was no difference in feel, there wouldn’t be any forged clubs! And if there’s no difference, why aren’t there cast tour muscleback irons? They’d be much easier casting shapes than GI/SGI irons - and a great opportunity for club makers.

It’s simply not true there’s no difference between a forged and a cast head even if they’re the same geometry.

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There have been cast muscle back irons.  Cleveland made some at one time.  IIRC, Vijay Singh used them.  I think (not certain) the Feel irons were cast.  I think Dave is right that the sound of the soft metal used in forged clubs is a large part of their perceived feel.  I wonder if you had a golfer with ear plugs blocking his hearing hit a forged iron and a cast iron of exactly the same design if he would notice any difference.  In my experience, I have hit both forged and cast irons that "felt like butter" when hit on the sweet spot.

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14 of the following:

Ping G425 Max

Callaway Epic Max 5 wood

Cobra F9 Speedback 7/8 wood set at 23.5 degrees

Callaway Epic Max 11 wood

PXG 0311P Gen. 3  6-GW

PXG 0211 5-GW

PXG 0211 sand wedge bent to 53 degrees

Maltby M Series+ 54 degree

Ping Glide 3.0 Eye2 58 degree

Ping Glide 3.0 60 degree

Evnroll ER2

Ping Sigma 2 Anser

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6 hours ago, Hook DeLoft said:

There have been cast muscle back irons.  Cleveland made some at one time.  IIRC, Vijay Singh used them.  I think (not certain) the Feel irons were cast.  I think Dave is right that the sound of the soft metal used in forged clubs is a large part of their perceived feel.  I wonder if you had a golfer with ear plugs blocking his hearing hit a forged iron and a cast iron of exactly the same design if he would notice any difference.  In my experience, I have hit both forged and cast irons that "felt like butter" when hit on the sweet spot.

Proof by exception? The fact remains tour muscleback irons are overwhelmingly forged. The fact remains casting yields different properties than forging. And the fact remains casting is cheaper than forging, so club makers would cast every iron club if there was no difference due to the alloys and material properties available in forging. Casting has a place in the golf world, they make more forgiving shapes possible that could not be achieved through forging - and some players value forgiveness/distance over feel. And I couldn't find evidence of a Cleveland cast muscle back, but I will take your word for it they were once manufactured.

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  • Titleist TSR2 16.5º HZRDUS Red 60 6.0 & TSR2 21º HZRDUS Black 4G 70 6.0 w Lamkin UTx Midsize
  • Mizuno JPX900 Forged 4-GW, S18 56.10, S18 60.06 w MCC+4 Midsize
  • Evnroll ER5B Fit@TrueSpec w P2 Touch Tour
  • Maxfli Tour & ProV1
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Rebound or trampoline effect is a small component of distance or feel. As indicated design that allows you to hit the “sweet spot”  consistently is more important than metallurgy. The feel of forged irons is however a real phenomenon and for highly skilled players can make a difference in performance. I’m not sure where that level starts but it has to be near scratch. For those of us less skilled players less feel & more forgiveness is likely to lower scores. My old forged clubs from the 70’s & earlier gave more feedback on Mis-hits in the form of shorter off line shots & more vibration as did the old persimmon woods.

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The sound of a long drive is so much cooler when your playing partner says “Wow”

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Some of you have forced me to question my thoughts on the topic.  I think you are right that sound is different for different types of steel.  Based on that, there probably are players who can feel differences but, for me, the difference is in sound.

14 of the following:

Ping G425 Max

Callaway Epic Max 5 wood

Cobra F9 Speedback 7/8 wood set at 23.5 degrees

Callaway Epic Max 11 wood

PXG 0311P Gen. 3  6-GW

PXG 0211 5-GW

PXG 0211 sand wedge bent to 53 degrees

Maltby M Series+ 54 degree

Ping Glide 3.0 Eye2 58 degree

Ping Glide 3.0 60 degree

Evnroll ER2

Ping Sigma 2 Anser

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Lots of interesting info on this thread. The real world difference between forged and cast clubs isn't something to really be worried about. Forged irons are simply clubs that have been made by beating a piece of metal into the shape of the head or in some cases face of the club. Cast clubs are simply molded. This is a very simplistic answer that doesn't answer all the different types of club making but to go any deeper would be losing sight of the forest from the trees.

In terms of real world performance between the two, there isn't any measurable difference. The things that causes clubs to perform differently is design choices and not so much the method they are made. Clubs with variable thickness faces (VFT) kind of help with off center distance using the "trampoline effect". However, the trampoline effect on irons (6 iron and shorter) is minimal since most people generally don't swing fast enough for faces to flex much and irons themselves are much shorter than a driver or 3-wood. The largest factor when it comes to distance is loft. 

Regarding feel, this is where confusion sets in. Forged irons generally are considered to feel and sound better when struck well but this is arguable. I personally think forgings can feel better but I even question it sometimes. The design of the club has more of an impact on feel and sound than how it's made. What makes a club feel solid is when we hit the ball with the center of gravity (COG) of the club head below the ball's center of gravity. This is why many game improvement (GI) cast clubs actually feel better to golfers who aren't the best ball strikers (most of us). GI irons typically (not always) have a lower COG than that of forged players irons. So generally speaking, GI clubs that are usually cast will actually feel more solid to more golfers. Cast or forged doesn't matter. 

When it comes to the pros, they tend to play less forgiving blades and players irons that are forged. They can probably feel and hear the difference between a forged and cast club but it's not really a determining factor of performance. Bubba won lots of PGA events using his cast Ping S59s and several other pros have won using the cast Ping i-series irons. For pros, the biggest performance factor is consistency and that typically means they aren't looking for irons that can give a significant "trampoline" effect because they don't need the ball the go farther, they just need it to go the same distance every time. So for pros, cast vs. forged is mostly a feel or preference issue but even then, it's not as big of an factor as many would lead you to believe.

So at the end of the day, don't let forged vs. cast be a determining factor. Choose clubs that have the best design for you and appeal to you. Trying to split hairs on feel between the two is getting into the minutia of golf and is more of a question for keyboard warrior enthusiasts that thinks it makes a material real world difference. 

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On 5/17/2021 at 4:26 AM, Specneeds said:

Rebound or trampoline effect is a small component of distance or feel. As indicated design that allows you to hit the “sweet spot”  consistently is more important than metallurgy. The feel of forged irons is however a real phenomenon and for highly skilled players can make a difference in performance. I’m not sure where that level starts but it has to be near scratch. For those of us less skilled players less feel & more forgiveness is likely to lower scores. My old forged clubs from the 70’s & earlier gave more feedback on Mis-hits in the form of shorter off line shots & more vibration as did the old persimmon woods.

True--- Anyone who does not believe it should hit a blade 2 iron on a cold day with a range rock-- Better pure it because if not the sting and vibration is enough to shake your teeth out of your head

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