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Some Technical Terms Defined
BOUNCE
The amount of space between the leading edge and the groundline when the club is in the square address position. In general, more bounce is better for soft sand, lush grass and for golfers with a steeper angle of attack into the ball; less bounce is better for firm sand, short cropped turf and golfers with a more level angle of attack into the ball. A slight amount of bounce on all the irons is also helpful when playing on fairways of creeping type grasses typical in hot weather areas such as Bermuda or Kikuyu, etc.
BULGE
The face curvature from heel to toe on drivers and fairway woods. Bulge is required on all woodheads to offset the natural draw or fade action of the ball when impact occurs off center toward the toe (draw shot shape) or heel (fade shot shape) side of the face.
CAMBER or SOLE RADIUS
The radius measurement of the sole from front to back, or heel to toe.
CAST
Two Types of castings - see below
DIE CAST
A method of clubhead manufacture in which the molten metal from which the head is to be made is poured/injected directly into a hard steel mold. Die casting is typically used to make clubheads which are made of softer metals such as aluminum or zinc and used to make heads of lower cost or which do not have a high strength requirement, such as thick face aluminum woodheads, cheap low end ironheads or putter heads.
INVESTMENT CAST
A method of clubhead manufacture employed to make heads from higher strength and higher hardness metals and/or when greater head to head repeatability in head shape and style features is required. The process starts with a special wax material injected into the clubhead mold to make multiple numbers of wax heads. Like wax heads are melt attached to a wax frame, then coated with successive layers of heat resistant ceramic material. Upon completion of the ceramic shell, the wax heads are melted out of the shell, after which the molten metal chosen to make the heads is poured into the empty shell. Upon cooling and solidification of the metal, the ceramic shell is broken away, the heads are sawed from their frame and then subjected to polishing and finishing procedures to complete the clubhead.
CC
A cubic centimeter is the unit of measurement for clubhead volume.
CENTER OF GRAVITY (CG)
The single point of equilibrium inside a clubhead. Also defined as the intersection of all possible balance points inside the body of the clubhead. It's the internal point about which the head rotates when impact with the ball is off center. A low CG helps to launch the ball slightly higher.
CNC MILLED
Computer Numeric Code Milling. Refers to the process by which an automated milling machine cuts and shapes the clubhead from solid blocks of metal by reading a special programming code. Scoreline grooves and clubfaces are often made this way to ensure accuracy and tight tolerances.
COEFFICIENT OF RESTITUTION (COR)
Used by manufacturers to define the spring like effect of a clubface. The USGA limit for the COR is .83, which refers to the efficiency of energy transfer between two colliding bodies (clubhead and ball). For example, if a ball is projected at a face at 100 miles per hour, it must bounce off at 83 mph or less for the club to be conforming within the 0.83 COR limit in the Rules of GOlf.
CUPFACE
In this construction the faceplate is part of the front portion of the crown, sole and skirt. This pushes the joining seam that attaches the face to the body of the clubhead farther from the face, thus allowing a slightly greater area around the perimeter of the face to be eligible for face flexing.
FLANGE
The part of a putter closer to the ground that projects back from the rear side face.
FORGED
A way of manufacturing a clubhead in which heated metal is stamped, pressed or hammered into the desired shape. The perceived advantage of forging is to more tightly pack the grain structure of the metal.
LEADING EDGE
The most forward part of the sole, at the very bottom of the face,
MOMENT OF INERTIA (MOI)
The amount of resistance of an object to being set in motion to rotate about some defined axis. In golf, the clubhead itself as well as the entire assembled club both have defined Moments of Inertia. For the clubhead, the most pertinent MOI to shot performance is the measurement of resistance to the head twisting around its Center of Gravity when impact with the ball occurs off center. The MOI of the clubhead may also be thought of as “off-center hit forgiveness,” because the higher this MOI, the less energy loss occurs from an off center hit. The USGA limit for this particular MOI for drivers is 5,900 grams/cmē. The MOI of the fully assembled club is defined as the amount of resistance the assembled club has to being swung around the golfer’s spine axis in the full swing motion, or to being swung through impact around the axis of the unhinging of the golfer’s wrist-cock release. Golfers who are physically weaker and who swing with much less downswing acceleration and force typically hit the ball more consistently with clubs that have a lower MOI. Golfers who are physically stronger and who swing with greater downswing acceleration and force typically hit the ball more consistently with clubs that have a higher MOI.
TOE HANG
The angle the putter head from toe to heel deviates from vertical when the assembled putter is laid on a flat surface such as a table top. In general, the greater this angle, the more suited the head is to an arced putting stroke as opposed to a putting stroke that is straight back and straight through the ball.
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