Iron (golf)

Irons in a golf bag

An iron is a type of club used in the sport of golf to propel the ball towards the hole. They are so-called because historically the clubhead was generally made from iron. Whilst the vast majority of modern irons are still made from iron, it is almost always its stronger and more durable alloy, steel.

There are three main components to an iron, the club head, the shaft and the grip. The face of the clubhead, used to strike the ball, is scored with grooves designed to impart spin, enabling the skilled player to more easily control the ball.

A standard set of 14 golf clubs will contain many irons, which are customarily differentiated by the angle of loft on the clubface, although they will also vary in clubhead size, shaft length, and hence lie angle. Irons are usually numbered, with the 1 iron having the lowest loft, smallest clubhead and longest shaft, through to the 9 iron and wedges, which have the greatest loft, largest heads and shortest shafts. These different characteristics allow different irons to be used from a variety of situations, from the teeing ground, fairway, rough, or from within hazards, such as bunkers.

Design and manufacture

Historically all irons were forged from a flat piece of metal, which produced a thin clubhead that resembled a blade. Modern investment casting processes enabled manufacturers to easily mass produce clubs with consistent properties. This manufacturing process was first used by PING,^[1] and also made it possible to take weight out of the back of the clubhead and distribute it around the perimeter. These perimeter weighted, or cavity back, irons made it much easier to achieve consistent results even when striking the ball outside the "sweet spot", when compared with traditional bladed, or muscle back, irons.

Although most irons are now produced by investment casting, many high end, particularly muscle back, irons are still produced by forging, as it is believed that the resulting club has an improved "feel". Manufacturers sometimes try to combine the characteristics of both muscle and cavity backed irons, which has resulted in terminology such as cut-muscle, or split-cavity.

There are also many hybrid clubs, so-called because they combine some of the characteristics of irons and woods, that closely resemble standard irons. Indeed, many sets of clubs, especially those marketed for beginners, now include hybrids to replace the more traditional 3 and 4 irons.

Muscle back

A muscle back is the more traditional design and consists of a solid head with little or none of the weight being distributed around the perimeter of the head. As such they require a great deal of skill in order to hit the ball consistently because the "sweetspot" is fairly small. In addition, any shot that is struck "off-center" may be severely compromised in terms of distance and direction.

Perceived advantages of muscle backs are that, when hit correctly, they provide greater distance than cavity backs, and much improved feel, although this is most likely due to the forging process by which they are usually made.

Cavity back

Cavity back, or perimeter weighted, irons are usually made by investment casting. They are so called because of the cavity created by the redistribution of the weight from the middle to the perimeter of the clubhead when compared with a traditional muscle back.

The perimeter weighting increases the size of the sweetspot and the moment of inertia of the clubhead, which reduces twisting when the ball is struck off-center, allowing such shots to lose less distance and accuracy when compared with a muscle back iron. More weight is often put into the sole of the clubhead, which lowers the center of gravity and increases the launch angle of the ball.

The forgiving nature of cavity backs combined with the ease with which they enable the average golfer to get the ball airborne, make them the most popular design of iron with amateurs.

Components

Clubhead

Investment casting, while allowing for a greater range of design options, produces a very stiff and inflexible head that can be difficult to adjust for a player's desired lie and loft. Forged irons, while they allow for easier and a greater range of adjustments are limited in the designs they may be achieved.

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.

Over the years, groove technology has changed the playability of irons. For the past 80 years, little has changed about grooves. However, a new rule by the USGA and the R&A^[2] has changed the way that grooves are to be made starting in 2010. In general, the deeper the groove, the more grass can be dispersed behind the ball at impact. This allows control over the amount of spin, which is crucial to flight characteristics of the shot as well as how well received the ball is on the green. The less that is between the ball and the club at impact, the more spin that will be produced which increases the flight trajectory and allows stopping quicker upon hitting the green. Better players benefit the most from deep, sharp grooves as the more clubhead speed is generated, the more spin the player is able to introduce. By forcing manufacturers to lessen the depth and cut on the grooves, the new rules will penalize shots from longer grass slightly more and put a premium on hitting the fairway.

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. 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 usable club face.

A stroke in which the ball comes directly off the hosel is known as a "shank", and the ball will usually veer off almost at right angles to the intended target line.

Shaft

Main article: Shaft (golf)

The shaft is the true engine of the iron. A shaft that is perfectly suited to the individual golfer increases distance and improves accuracy, while a poorly suited shaft can lead to inconsistent, wayward shots and reduced distance.

Although graphite shafts, made from composite materials such as carbon fiber, are now standard in woods, especially drivers, shafts for irons are still most often made from steel, which has lower torque than graphite, allowing less clubhead twisting, which gives better accuracy. Graphite shafts are not uncommon for numbered irons however, as the increased distance conferred by the shaft is advantageous to many players, especially shorter hitters such as ladies and seniors. Wedges virtually always have steel shafts as the accuracy and consistency is of primary importance.

The higher the number of the iron, the shorter its shaft will be, allowing the player a more controlled and consistent swing. The resulting reduction in clubhead velocity is overcome by an increase in clubhead mass.

Grip

The grip covers the top of the shaft enabling the golfer to hold the club comfortably. Modern grips are generally made from rubber, sometimes inlaid with cord, but some players still prefer a traditional leather wrap. Even though materials advances have resulted in more durable, longer-lasting soft grips, they still require frequent replacement as they wear, dry out or harden.

By the rules of golf, all iron grips must have a circular cross-section. They may taper from thick to thin along their length (and virtually all do), but are not allowed to have any waisting (a thinner section of the grip surrounded by thicker sections above and below it) or bulges (thicker sections of the grip surrounded by thinner sections). Minor variations in surface texture (such as the natural variation of a "wrap"-style grip) are not counted unless significant.

Types of irons

Numbered irons

The 1 iron, or driving iron, is the lowest lofted and longest iron, although Wilson did make a 0 iron for John Daly. Often called a butter knife because of its looks, the 1 iron is commonly regarded as the hardest club in the bag to hit, and is now virtually obsolete. Lee Trevino is famously quoted, after he had almost been struck by lightning at the 1975 Western Open, that if he were out on the course and it began to storm again he would take out his 1 iron and point it to the sky, "because not even God can hit a 1 iron."^[3]

The 2 to 9 irons traditionally made up a standard set of irons, although with technological advances, changes to specifications and preferences of the average golfer, the 2 iron is now generally omitted, and a pitching wedge included. A modern matched set of irons will often also have a sand wedge. The 2 iron's place in the bag is often taken by a third wedge. Increasingly, with the introduction of hybrid clubs that are easier to hit than the longer irons, the 3 and 4 irons are also omitted.

Due to the average golfer's desire to hit the ball farther, the loft on modern irons is much less than that on irons from even the late 20th century. For example a modern 9 iron has comparable loft to a 7 iron from the 1990s. Manufacturers have been able to reduce loft without compromising usability, by moving weight into the sole of the clubhead, thereby lowering the center of gravity and enabling the ball to be launched on a higher trajectory than would otherwise be the case.

Wedges

Main article: Wedge (golf)

Wedges are a subclass of irons which are designed for an array of specialist situations. Although similar in design and construction to other irons, they can generally be differentiated by having higher loft than the numbered irons, and a much wider sole, which provides more "bounce", enabling the club to easily cut through long grass, turf and sand without digging in. It is this wide sole that gives the wedge its name, alluding to the profile of its clubhead.

Wedges are used mostly for approach shots to the putting green, getting the ball out of tough situations, and to escape from hazards. They are designed to produce a high, short trajectory with a high degree of spin, all of which cuts down on the distance the ball will roll after landing. Most golfers will generally have at least two wedges, traditionally a pitching wedge and a sand wedge, with a lob wedge or a gap wedge commonly being added to provide additional options. Wedges are usually identified by their loft (56°, 62°, etc.) or letter denoting their function (PW, GW, SW, LW, etc.).

• The pitching wedge is the most similar in design and function to other short irons, sometimes even designated as a "10-iron", and is usually included in a set of matched irons.
• The gap wedge was created to fill the gap between the pitching and sand wedges. With modern pitching wedges having much less loft than previous generations, and because sand wedges had generally remained the same, another wedge was needed to fill this gap that had opened up between clubs. The gap wedge has a loft similar to that of an old pitching wedge, around 52°, and can also be found labelled as an "Approach", "Dual", "Utility", or "Attack" wedge.
• The sand wedge, or sand iron, is primarily designed for use out of sand bunkers. It has the widest sole of the wedges that provides the greatest amount of "bounce", which allows the clubhead to glide through sand and avoid digging in.
• The lob wedge has a high degree of loft designed to produce shots with a very high arc, and are most often used for shots over hazards and other obstructions.

• The ultra lob wedge is a highly specialized, extremely high-lofted lob wedge, that is designed for situations where an almost vertical launch is required. They are generally only made by speciality companies, and are not in common usage.

Given the choices available to the modern golfer, the traditional pair of pitching wedge and sand iron is starting to become less common as players opt for a selection wedges with an array of different lofts and bounce angles. For example, a player may pick two gap wedges, one with low bounce but greater loft than a pitching wedge, and the other with similar bounce but less loft than a sand wedge, then add a lob wedge and forgo both of the traditional wedges.

Specifications

The following table provides a guide to the typical specifications of modern irons.

Iron	0	1	2	3	4	5	6	7	8	9	PW	AW	SW	LW	ULW
Loft[nb 1]	11°	14°	17°	20°	23°	26°	29°	33°	37°	41°	45°	50°	55°	60°	64°
Lie[nb 2]	59°	59.5°	60°	60.5°	61°	61.5°	62°	62.5°	63°	64°	65°	65°	65°	65°	65°
Length (in)[nb 3]	40.5	40	39.5	39	38.5	38	37.5	37	36.5	36	35.5	35.5	35.25	35	35

The following table provides a guide to the typical specifications of irons through to the mid 1990s.

Iron	0	1	2	3	4	5	6	7	8	9	PW	SW
Loft	14°	17°	20°	24°	28°	32°	36°	40°	44°	48°	52°	56°
Lie	54°	55°	56°	57°	58°	59°	60°	61°	62°	63°	63°	63°
Length (in)	39.5	39	38.5	38	37.5	37	36.5	36	35.5	35	35	35

1. ^ Standard loft angles vary slightly between models of club.
2. ^ Different golfers require lie angles that may be as much as +/- 3 degrees than the standard ones listed.
3. ^ Standard lengths. Golfers may have different shaft lengths to suit their game.

References

1. ^ Brown, Clifton (February 18, 2000). "Karsten Solheim, 88, Is Dead; Creator of the Ping Golf Club". The New York Times. http://www.nytimes.com/2000/02/18/sports/karsten-solheim-88-is-dead-creator-of-the-ping-golf-club.html. Retrieved 2009-06-30. 
2. ^ "New Rules Will Impact Club Grooves". The Washington Post. August 6, 2008. http://www.washingtonpost.com/wp-dyn/content/article/2008/08/05/AR2008080503291.html. Retrieved May 5, 2010. 
3. ^ "1-iron clinging to life ... but barely". ESPN. December 15, 2005. http://sports.espn.go.com/golf/news/story?id=2258661. Retrieved 2009-07-01. 

External links

Golf portal

• Blade Irons Vs Cavity-Back Irons
• Public patent information on muscle-back iron
• Public patent information on cavity-back iron
• Public patent information on hybrid iron
• Golf FAQ