In the sport of golf, an iron is a class of golf club used to hit a golf ball. The situations in which irons are used vary widely, but are most often used when hitting an approach shot onto the putting green, a shot from the fairway on a long hole, and for "odd" shots such as hitting out of the rough, out from underneath trees or over the tops of trees, or out of hazards.
Some irons
Irons are generally used for shorter shots than woods. The set of irons has the widest range of uses of the clubs in any bag, and an iron in general is the most versatile club in terms of the variety of different shots that can be made with the same club. Irons range from numbers 1 (commonly called a "driving iron") to 9, and like woods, a lower number has less loft and a longer shaft. Irons with higher loft than a 9 are called wedges. The most common iron set consists of all numbered irons from 3 to 9 plus a pitching wedge and/or sand wedge, though many variations exist as with other clubs.
Irons are generally classified by their shaft length (which coincides with their range). The 1 to 4 irons are usually considered 'long irons', the 5 to 7 irons 'mid irons' and the 8-iron through the various wedges 'short irons'. This classification may differ from person to person, depending on skill level and preference. Longer irons are generally used for low, straight distance shots on long holes or from the rough, while shorter irons are used for approach and chip shots and rarely even for putting.
Design
The face of an iron is a flat wedge shape, taller at the toe of the club than the heel. The design of the back of an iron varies widely, though they fall into two types, cavity-back irons and muscle-back irons. Muscle-back irons have a solid back with a thick base, while cavity back irons have a hollowed out back, a 'cavity'. Mizuno's 'cut-muscle' design lies somewhere in between, neither fully muscle- nor cavity-backed, with behavior also lying in between the two design classes.
The muscle back design is the older style. These designs are also called 'blades' for their low amounts of offset and thinner edge-on profile. This nickname has become synonymous with difficult-to-hit irons, though modern blade design has made them slightly easier to hit. It is often said that "if you can hit a blade, you can hit any kind of iron". Despite this, muscle-back irons are preferred by players whose swing launches the ball on a higher trajectory, as the raised center of gravity lowers the flight path of the ball compared to other clubhead designs.
Cavity-back irons remove mass from the back of the club and move it lower and to the perimeter of the iron. This lowers the center of gravity and increases the moment of inertia (the resistance to turning due to mass distribution) of the clubhead, making irons more forgiving on off-center hits and launching the ball higher. This is not the same as an "enlarged sweet spot", which is technically the center of gravity, at which the force at contact is greatest. It merely gives less variation between a centered hit and an off-center hit, while increasing hangtime which generally increases distance. The tradeoff paid is greatly reduced "feel" of the club; because the clubhead resists twisting on an off-center hit, the player receives less feedback through the shaft about the clubface's position and angle at contact.
The typical lofts for numbered irons range from 16 to 48 degrees. Modern irons tend to have lower lofts than their older counterparts. This trend is partly due to the desire of average golfers to increase their distance with each iron. The design of modern cavity-back irons targeted for average golfers also demands less loft as compared to muscle-back irons designed for players of higher skill levels. The center of gravity in a number of modern cavity-back iron designs is so low that the trajectory produced by such an iron could be so high as to actually reduce the distance of the shot if the loft remained at the older standard for each iron. For example, modern pitching wedges may have lofts up to 45 degrees, similar to a traditional 8-iron.
Construction
Shaft
Shaft lengths on irons typically range from 36 to 40 inches (90-100 cm) in length. Iron shafts are most often made from steel, which has lower torque than a graphite shaft for less clubhead twisting and better accuracy. Graphite shafts for numbered irons are not uncommon however, as the increased distance conferred by the shaft is advantageous to many players especially ladies and seniors. Wedges however virtually always have steel shafts as the accuracy and consistency of a wedge shot is of foremost importance over raw distance. The shafts of higher-numbered irons, like that of higher-numbered woods, is shorter, allowing the player a more controlled and consistent swing. The resulting reduction in clubhead velocity is overcome by an increase in clubhead mass.
An alternative to the varying shaft lengths in irons as shown above was developed by David Lake of 1 Iron Golf, Inc. in 1998. Commonly referred to as single-length irons, same-length irons, or the 1 Iron Golf System, David Lake's concept was that all of the irons within a set should be the same length and incorporate the same clubhead lie angle. The only difference between irons within a set of single-length irons would be the clubface loft angles which would have the same progression as those within a conventional set. The basis of this concept is that the golfer needs to learn only one swing and use one ball position for all of the irons within a set as opposed to the 10+ swings and varying ball positions required with a conventional set of irons. [1]
Hosel
For irons, the hosel is very noticeable, forming a barrel shape on the inside face of the club and the "heel" of the sole of the club. It can be an annoyance to golfers who "shank" a shot off of the hosel, but many modern irons have a more offset hosel, integrated into the clubhead at a lower point and further from the hitting area of the club. This, combined with the perimeter weighting of modern irons, gives a club with the lowest possible center of gravity and the highest possible useable club face.
Clubhead
Traditionally, most iron heads were made by forging, which involves the careful shaping of the club head through hammering and pressing of heated steel. Today, most modern golf club heads of all types, not just irons, are cast through a process known as investment casting. This process allows manufacturers to redistribute the weight into the perimeter of the club, known as perimeter weighting, which helps to increase the accuracy of mishit shots.
Casting, while allowing for a greater range of designs, produces a very inflexible head that can be difficult to adjust for a player's desired lie and loft. Forged heads, due to their manufacturing process, are much easier to adjust by several degrees in any direction, so much so that the lie and loft of the club can change during the course of normal play. Owners of forged clubs may have to periodically check and "re-calibrate" clubheads to their desired specs.
The shaft length of an iron decreases as the iron's number increases; therefore the iron number is disproportional to its length. This reduced length means that a clubhead of the same mass traveling at the same angular velocity (degrees per second, as swung by a golfer) has lower momentum because the clubhead's speed is slower. To combat this, higher-numbered iron clubheads are heavier than lower-numbered iron heads; there is generally a 4oz increase in mass between one clubhead and the next higher number.
Wedges
Wedges are a subclass of irons which have a loft greater than that of a 9-iron (generally more than 44°). Although highly similar in design and construction to other irons, the purpose of wedges is more specialized, and thus they are often regarded as a class unto themselves. They give a very high, short trajectory with a lot of backspin(when hit correctly), all of which cuts down on the rolling distance of a ball after its initial impact. Wedges are thus used for a variety of high-accuracy "utility" shots, such as lofting or chipping the ball onto the green, out of a sand trap, or over or around an obstruction such as trees, rocks or sudden changes in terrain level. A set will generally have two, sometimes three wedges: the traditional pair is a pitching wedge and a sand wedge, to which modern golfers generally add a lob wedge or a gap wedge. Wedges are seldom numbered, being identified instead by their loft (56°, 62°, etc.) or their function:
The pitching wedge (generally labeled "P", sometimes "W") has a loft of 44-50 degrees and is rather similar in design and function to other short irons. In fact, in older sets the pitching wedge often had the designation of "10-iron" and even today most matched sets of irons include a pitching wedge as if it were a numbered iron.
A sand wedge ("S") has a specially designed underside that provides "bounce", allowing the sole to skim over sand and avoid digging in, which combined with a loft of 54-58 degrees makes it suitable for shots from bunkers or from deep rough. Older sets sometimes called this the "11-iron" or "sand iron"; the purpose was the same.
The gap wedge (sometimes "G", but commonly "A", "D", or "U") has a loft somewhere between a pitching wedge and a sand wedge (50-54°). Modern pitching wedges have lower lofts than previous generations, while sand wedges have generally remained the same. The "gap wedge" was introduced to fill this gap between lofts, hence the name. This is the newest type of wedge and as such has little standardization of design, purpose or even name; Wedges in this general range of loft with varying amounts of bounce have been called "Approach", "Dual", "Utility", or "Attack" wedges and designed for a multitude of lies from sand to rough to fairway, depending on player preference.
The Lob wedge ("L") has a very high loft (up to 70 degrees, most commonly 60) and is used for the shortest lob shots (generally 10-45 yds) such as close approach shots, from sand, or difficult recovery shots requiring an extraordinarily high shot and short distance. The highest-loft variations (64° and over) are sometimes called "Ultra Lob", "Flop" or "Final" wedges, used for specialized, extremely high-angle shots such as from the "lip" of a bunker. These are generally made by specialty companies and some argue that their purpose is redundant, as a 60° lob wedge or even a sand wedge can be "opened" for extra loft in situations calling for such a high launch angle.
Given this wide array of choices, the traditional pair of pitching and sand wedges is starting to become less common as players can choose variations of gap wedges to fine-tune the spread of their wedges' lofts. A player may pick an "approach" wedge with low bounce but greater loft than a pitching wedge, say 50°, and a "dual" wedge with a similar bounce but less loft than a sand wedge (like 54°), then pick a 60-64° lob wedge and forgo both of the traditional wedges.
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