Effects of Clubhead Features:
Material and Manufacturing Process
This section is mostly about steel: carbon (forged) vs various forms of
stainless (cast). But we will also mention composites, wood, and
titanium where they are relevant.
There are quite a few dimensions to the choice of material
for a clubhead:
The "feel" and "playabiity" of
- The distance
the clubhead can hit the ball.
- The weight of the
or the peripheral weighting (forgivingness) that can be achieved.
required for the clubhead.
- How much can the clubhead be adjusted
to achieve different playing characteristics (e.g.- bending for loft
Forgivingness and workability
has been a lot of controversy about the ability of forged vs cast
stainless steel (the usual cast clubhead) vs chromed carbon steel (the
usual forged clubhead), with respect to how they forgive off-center
hits. Alternative, it is framed as how "workable" the shot is by
deliberately hitting off center. On the basis of the published results
controlled tests, I believe that material has very little to do with
it. The difference is mostly in the design
of the head. That is, usually
The few studies that played mix-and-match with these
relationships (for instance, cast stainless musclebacks) came away
concluding that the difference in "feel" was really the difference
between a cavity back (big sweet spot) and a muscle back (small,
critical sweet spot). The material had nothing to do with it.
Still, a lot of golfers seem to believe that a softer
clubhead material changes the feel of the club, and there are
manufacturers out there encouraging this belief and producing clubheads
to sell to it. So let's analyze whether there's anything at all to it...
The "softness" of feel is a combination of the softness
of the clubhead and that of the ball. More precisely, the softness of
feel is the inverse of the total
stiffness of the collision between
ball and clubhead. Stiffness is measured as a force divided by the
deflection produced by the force,
designated "force/deflection". The lower this ratio (either due to
reduced force or a longer compression), the softer the collision feels.
During impact, both
the ball and the clubhead deform and produce elastic
Consider the compression stiffness of each of the two materials:
In an "elastic collision" like that of the ball and clubhead, the
overall stiffness of the collision is:
- Force/deflection for the clubhead material is Kh.
- Force/deflection for the ball is Kb.
Of course, steel -- any kind of steel -- is much stiffer
in compression than a golf ball. That is, Kh
is greater than Kb,
factor somewhere between a hundred and a thousand. A little algebra
will show us where this is going. The overall stiffness of the
collision is completely dominated by the stiffness of the ball; the
metal of the clubhead has very little to do with it.
many times larger than Kb, Kb+Kh ≈ Kh , so:
How about a few examples to
show us that the stiffness of the collision is dominated by the ball's
construction, not the clubhead's. Let's assume the ratio of Kh to
100, just to give the greatest possible chance to show that clubhead
material does matter.
Actually, the domination is even more marked than the above numbers
suggest, because steel is more
100 times stiffer than a golf ball. Bottom line: if you want a softer
feel, get a softer ball; the clubhead material won't do anything for
- From the softest steel to the hardest, the range
is only a 10% range. Suppose forged carbon steel were a full 10% softer
than cast stainless. Then wouldn't the collision feel 10% softer? No,
it wouldn't. From the equation, a 10% reduction in Kh
in only a 0.2% reduction in overall stiffness of the collision.
- Well then, let's choose a really
soft metal like copper, and use it as an insert. (As I originally wrote this in the 1990s, such
a set of irons had appeared on the market.) Even copper, at only half
the stiffness of steel, results in only a 1.0% reduction in the overall
stiffness of the collision. Not even the most practiced pro could feel
this; even if he/she could, ball-to-ball variation is considerably
greater than this.
- Finally, suppose we reduced the ball's
compression by 10%. This time, the collision is in fact 10% softer. So
the compressibility of the ball dominates the feel of the collision.
Feel again, but really sound
look at another rationale for believing that clubhead material can
affect feel. And this one, as counterintuitive as it is, has the best
chance at being real. More than one study has concluded that sound
is a major
component of what golfers call "feel". These studies typically used
various sound "shapers", from a low-pass filter (removes the high
frequencies) to complete blockers of all sound. A couple of interesting
I have an anecdote about this. Admittedly not a controlled
experiment, but it adds a data point. A member of my regular foursome
-- in fact, our "A" player -- wears a hearing aid, which he rather
needs. One round, the his hearing aid broke late in the front nine. (I
think the battery ran down, but I'm not sure.) After the round was
over, he told me that he got no feel from his clubs the entire back
nine. Take it for what it's worth.
- Clubs tested with low-pass earplugs were reported by
golfers to have a softer feel
than clubs tested without earplugs.
- Clubs tested with high-pass earplugs were reported to feel
harsh or hard.
- With complete sound-blocking earplugs, the golfers
were unable to consistently distinguish the feel of the various clubs.
Can this play back into cast vs forged steel clubheads? Very
possibly. The forged clubheads are "softer" in the sense that they are
more malleable. That is, they can be made to take a permanent bend more
easily. (More on that below.) Consequently, it might be expected that
they would damp out the higher frequency sound components.
Time on clubface
In the late 1990s, golf club companies (probably Callaway first) started increasing the coefficient of restitution (COR) of
their drivers by making the clubface thinner so it would flex more. The
result was an increase in distance.This was in violation of the rules, but it wasn't discovered until
there were many thousands of the non-conforming clubs in the hands of
golfers. By 2003, the ruling bodies (USGA
and R&A) agreed to regulate COR to a maximum of 0.83. Measuring COR directly is an expensive proposition; it needs a
precise-velocity cannon for golf balls and the ability to
measure the golf ball's velocity. So a few years later, the ruling
bodies agreed on an indirect measurement that was strongly correlated
to COR. They bounced a pendulum bob off the clubface and measured the
time the pendulum was in contact with the face. The longer the pendulum
was on the clubface, the higher the COR.
Since the inception of this "characteristic time" test (CT), the belief has
grown that keeping the ball (not a steel pendulum bob, but a
golf ball) on the clubface longer imparts some mystical, magical
properties to the golf shot. I have seen claims of more distance, more
energy transferred to the ball, more spin, and better control. Of
course, some club manufacturers and instructors are selling all sorts of snake
oil purporting to keep the ball on the clubface longer.
It is time to debunk this. Note that it takes two leaps of reasoning to sell the improvement: (1) a longer time on the clubface
imparts these magical properties, and (2) my product/technique will
keep the ball on the clubface longer. Do away with either #1 or #2, and
you debunk it.
- No extra distance nor energy transfer occur just because
the ball is on the clubface longer. The myth comes from the correlation
with the COR test. But, as everybody is saying the last couple of years
(as science has come more publicly into golf), correlation is not the
same as causation. And it is particularly silly when it is in fact cause
and effect -- but the proponents have gotten it backwards. As they have in this
case. Something that does in fact increase energy transfer and distance
-- thinning the clubface for a spring effect -- will as a by-product
increase the time the ball stays on the clubface. That hardly means
that keeping the ball on the clubface will in general improve energy
transfer. Let's look at clubhead material, for instance. Consider two
- Titanium can increase energy transfer, but not just
because it's titanium. Titanium allows the construction of thinner faces
than steel, which flex more and thus add to COR. The increase
in contact time is a by-product, not the cause of the higher ball speed.
- Forged irons are more malleable than cast irons. Let's
suppose they are enough softer to make a noticeable difference in the
time on the clubface. (They
are not that much softer! But let's just assume, and see
where it takes us.) They are softer because they are more malleable. To
that extent, they absorb energy during impact; they do not give back
all the energy of their spring deformation. So any increased
time-on-clubface due to soft, malleable iron faces would result in lower COR, not
- OK then, how about spin? For a full shot, spin is almost
entirely a function of the ball. In fact, high spin balls might
spin if you could keep them on the clubface significantly longer. (As
we did above, we will assume a longer contact time to see what would
happen, even though it is contrary to fact.) According to an article by Bill Gobush
of Titleist, high-spin balls are "tuned" to give maximum spin for a
particular time in contact with the clubface. The internal shear
stresses between and within the layers of the ball get relieved, ideally, as the ball leaves
the clubface. If we could keep it on the clubface significantly longer,
the stresses would build in the opposite direction and retard spin.
This is mostly an argument based on face hardness. Here's a
more on why that is not really an issue.
If you're a fan of lighter-than-standard weight or
peripheral weighting, then graphite and titanium may hold some exciting
appeal for you. Both these materials are lighter for a given volume
than steel, so they offer the possibility of lighter overall clubheads,
or at least lighter faces or inserts.
The whole clubhead can be made of graphite or titanium.
We see quite a bit of this now in metalwood clubheads. There is the
opportunity to make performance improvements with the lighter material:
Another approach is to use a combination of materials in the clubhead.
Here are a few real-world examples:
- Overall lighter clubhead, for lower swingweight or
longer clubs. Theoretically this should give more distance. There are now oversize
driver heads on the market with weights as low as 190 grams, and even
lower is feasible with titanium.
- Bigger clubhead, for more forgiveness. This seems to
be where everyone is putting their titanium, and some are putting their
- Thicker cross sections, for a stronger clubhead. This
is where some of the titanium is going.
- Titanium clubfaces in otherwise steel clubs have several
advantages. They allow more peripheral weighting for forgivingness. And
they allow a springier face for a higher COR. In the 1990s, when
titanium clubheads were very expensive, we saw some steel metalwoods
with titanium faces for these reasons. And today we see irons with
faces of either titanium or specially treated steel to give a higher
COR than we normally think of for an iron.
- Most clubs perform better with a lower center of gravity.
Part of this can be done by designing the shape. But the last two
decades have seen designers get really creative in the use of materials
to lower the CG of a clubhead. Cases in point:
- Historically, I date this trend to the TaylorMade Rescue
club from the late 1990s. Most people consider the originality of this
innovative club to be the hybrid shape. (Even today, I hear a lot of
non-TaylorMade hybrids incorrectly referred to as "Rescues".) But one
of the reasons it was such a superior design was the use of materials.
The top half of the body was made of titanium (the lightest of the
clubhead metals) and the bottom half of tungsten (the heaviest). The
result was a standard clubhead weight, but an extremely low CG; it could get the
ball airborne much more easily than its competitors. Incidentally, the
Orlimar metalwood of about the same vintage advertised tungsten sole
weights; they were just thin tungsten foil, and were but a fraction of
the weight needed to make a significant lowering of the CG.
- We have seen "composite" driver heads -- mostly-titanium
bodies with carbon fiber crowns -- intended to lower the CG. Carbon
fiber is not as strong nor stiff as titanium, but considerably lighter.
As long as the shock of impact is absorbed by the titanium, the thin
carbon crown keeps the club together and streamlined while minimizing weight high in
- Finally, let's look at the Acer XS titanium 3-wood from Hireko Golf. In 2013 designer Jeff Summitt
asked himself, "What if I built a low-profile 3-wood out of titanium
and gave it a spring face?" With a much smaller head than a driver, it
it turned out not to need much material for strength. You could easily
build it to a weight under 130 grams. But, since a
properly-performing 3-wood head is about 210 grams, that sounds pretty
useless. It isn't! Jeff used the 80g difference for discretionary
weight (probably stainless steel) to be put in the sole, as low as it
could be placed. The result is in my own bag, and it is by far the best
3-wood I have ever hit.
There are several maintenance issues that separate the
The most obvious of these is rust. The carbon steel of a
forged head needs to be chrome plated to prevent the head from being
destroyed by rust. Scratches in the chrome show oxidation fairly
quickly. The other materials (stainless steel, graphite, and titanium)
are quite inert and don't rust.
brings up a potential problem: some kinds of maintenance of forged
irons will just invite rust. For instance, a regrooving tool, used to
restore worn grooves, is likely to remove the plating and the grooves
will quickly rust. And I do mean quickly;
it is hard to clean and dry the grooves, so they stay moist when you
put the clubs away. Even worse is grinding the sole, which is a common
modification to wedges; better golfers want their wedge soles shaped to
facilitate shots they like to play. If you're going to do this, you
should probably have the clubhead re-chromed afterwards.
Wood and fiber composites scratch and abrade more easily than
titanium or steel. Wood is pretty straightforward to maintain, for
anyone who got through high school woodworking shop, but graphite
(carbon fiber) is
Of the stainless steels, 18-8 and 304 are the softest
(most "scratchable"), and 17-4 the hardest (most scratch-resistant).
I have never tried to refinish a metalwood head, but
that's only cosmetic anyway. I'm less concerned about the club's looks
than its playability or integrity. But for those who do worry about
cosmetic issues, metalwood refinishing kits are available.
What happens when you need to adjust the loft or lie of
the club? Most irons can be adjusted by bending them at the hosel. But
thinking of adjusting a carbon fiber ("graphite") or wooden head, stop
it. (Well, I have adjusted the loft of wooden heads with a file and
then refinished them. But those heads are rare and becoming more so.)
As for the various kinds of metal used in golf clubs:
- Carbon steel (as used in forged
irons) is very bendable.
- 18-8 and 304 stainless steel (used
in a small and decreasing number of cast iron heads) is similarly
- 431 stainless steel (the most
common material for casting iron heads) can be bent a limited amount.
The usual rule of thumb is no more than 2 degrees of bend.
- 17-4 stainless steel (used in
almost all metalwoods and a few iron heads) shouldn't be bent without
"special equipment", according to the 1995 Golfsmith catalog. (I have
been successful myself on one occasion at bending a 17-4 clubhead 2.5
degrees. I have also seen broken 17-4 clubheads after an attempted bend
of only 1 degree.)
- 15-5 stainless steel I have only
seen in metalwood heads, and have never heard of its being successfully
in metalwood heads may be bendable. According to Mitchell Golf
(which makes the best-known bending machines), forged titanium has a
softer structure than cast. BTW, there is lots of good information
about bending in the Mitchell article.
The reason for this is the hardness of the material. The
less sure you are of your loft/lie, the higher on this list you want to
be. By the same token, harder clubheads will not nick as easily and
will probably last longer; if you ARE sure of your loft/lie, move
toward the bottom of this list for a club that will look better longer.
Last modified Aug 26,
My thanks to Bob
for asking questions that led me to rewrite this page,
it not having been
touched since 1998.