We are going through the club fitting variables in Golf Club Fitting with PGA Professional Gary Balliet. Over the first few weeks, we’ve covered length, lie angle, and shaft flex. Club fitting variable No. 4 is head design.
Different players prefer different clubs based on the way they look, but there’s a lot that goes into designing a club head, and the design influences both distance and direction.
Irons Only
There are several types of irons on the market: blade or muscleback, cavity back or perimeter-weighted, low profile, and sole-weighted blades.
Irons are made of 17-4, 304, or 431 stainless steel or they are made of carbon steel through one of two processes: forging or investment casting. Of the two, forging is more expensive. That’s because each iron head is made using a series of forging dies and stamping to get the head to its final shape. Forged clubs are easy to adjust for lie angle because the metal is softer.
Investment casting, which is commonly used to make irons, putters, and metal heads, uses a master mold, liquid metal, and then a cooling process. This makes adjusting the clubs for lie angle nearly impossible because the metal is so hard. PING is famous for its cast metal clubs, and the process is a lot less expensive than forging. Players either have to send their clubs to PING or go directly to the factory in Phoenix to have their irons adjusted. Here is a video of Mizuno’s iron forging process:
Center of Gravity
All clubs are designed with the center of gravity (CG) in mind. A low or back center of gravity produces a high ball flight, and a high or forward center of gravity produces a low ball flight. Irons can be low or high profile, offset, non-offset or on-set, and even progressive. Offset heads, which are the most common, produce a high ball flight. Non-offset heads like drivers and putters produce a low ball flight. Progressive sets literally “progress” from traditional short irons to more hybrid-type long irons.
Drivers, Fairway Woods, and Hybrids
Metal heads can have deep or shallow faces, be bi-metal or tri-metal, and can be made of stainless steel or titanium. The USGA limits the size of a metal head to 470cc’s (cubic centimeters). A deep face has a high center of gravity and produces a low ball flight, while a shallow face has a low center of gravity and produces a high ball flight. The type of head a player should use is best determined by looking at the centeredness of hit during a dynamic fit.
In Review
Low and/or push in ball flight
On-set, deep face, high profile, high or forward CG, and CG toward the toe
High and/or pull in ball flight
Offset, shallow face, low profile, low or back CG, and CG toward the heel
Did You Know?
Gear effect is the term used to describe the action of the clubhead during impact with the ball. A shot hit off the toe of the club (for the right-handed golfer) will generate counterclockwise spin and will curve in a draw or hooking in what is commonly referred to as a “toe hook.” A shot hit off the heel of the club will generate clockwise spin and will curve in a fade or slicing motion.
Terms of Endearment
Coefficient of Restitution (COR) = The relationship between the rebound velocity and the initial velocity (also known as the trampoline effect) of the ball off the clubface.
Characteristic Time (CT) = how long the ball stays on the face based on the COR. The USGA sets a limit of 257-microseconds (millionths of a second), but it’s characteristic time is 239-microseconds.
Moment of Inertia (MOI) = the resistance of twisting of any club head when that head is impacted off center. The higher the MOI, the better. Manufacturers don’t actually ever increase the size of the sweet spot on a golf club, which is about the side of a pin needle. Instead, they create clubheads with a higher MOI.
Portions of this post courtesy of Wishon Golf.