Posted 01 February 2006 - 05:00 PM
Here is what is stated in the rules of golf appendix II:
Appendix II, 5a states that:
The material and construction of, or any treatment to, the face or clubhead must not have the effect at impact of a spring (test on file), or impart significantly more or less spin to the ball than a standard steel face, or have any other effect which would unduly influence the movement of the ball. The face of the club must be hard and rigid (some exceptions may be made for putters) and, except for such markings listed below, must be smooth and must not have any degree of concavity.
If claims of added spin are made by the manufacturer, or if there is strong supporting evidence of added spin, then the club would be deemed to be non-conforming.
With respect to woods and irons, if a club does not appear on the USGA’s current non-conforming list, it will be deemed non-conforming if the manufacturer clearly claims it is non-conforming, exceeds USGA limits, or makes other statements of non-conformance.
The “hardness” rule is particularly relevant to putters which have a urethane or other “soft” material inserted into the face.
The measure for ‘hardness’ is made using a durometer. A putter face must have a hardness of no less than 85 on a Shore A scale durometer. A simple measure of hardness “in the field” would be to use a fingernail. If pressing a fingernail leaves a significant imprint in the face of a club, please consult the USGA and offer a Duration of Competition or Duration of Round ruling. The face of a wood or iron club must be substantially harder than a putter face, i.e., no less than 75 on a Shore D scale.
In the field, ‘rigidity’ is interpreted to mean that the face should not have any visible signs of movement or flex when pressure is exerted.
b. Impact Area Roughness and Material
Except for markings specified in the following paragraphs, the surface roughness within the area where impact is intended (the “impact area”) must not exceed that of decorative sandblasting, or of fine milling. The whole of the impact area must be of the same material. Exceptions may be made for wooden clubs.
For iron clubs, the ‘impact area’ is deemed to be that part of the face which lies within 0.80 inches (20mm) on either side of the vertical center line of the face, but excluding strips 0.25 inches (6.35mm) wide from the top and bottom edges (see Figure 38 — Design of Clubs, Section 5d).
For metal wood clubs, the shape of the impact area is generally based on the traditional inserts used in persimmon type wood clubs. The shape and dimensions of this area can best be illustrated as follows:
The height (h) of the trapezoid is used to fix the horizontal dimensions — namely “½h” at the top and ‘h’ at the base. This ensures that all impact areas are similar.
Metal wood club faces which have inserts of different material, not trapezoidal in shape, may be permitted if the height of the insert meets the above requirement and the width of the insert is the same height in at least one point. However, in order to preserve the intent of the ‘same material’ rule (further explanation follows), clubs which have unusually shaped inserts of different material (i.e., other than circular, oval, square or rectangular) would not normally be permitted.
If an insert of different material is permitted under the above guideline, the insert would be considered the ‘impact area’ for that club. Therefore, any markings outside that area need not conform to the specifications provided in Appendix II, 5c. However, such markings must not be designed to unduly influence the movement of the ball.
When dealing with the surface roughness of a club face (not including putters, see Design of Clubs, Section 5f), the claims made by the manufacturer must be taken into account — especially if there is a claim that the roughness of the face influences the movement of the ball. In the absence of such claims, the ruling would be made purely on the amount of roughness in the impact area. Sandblasting or other treatments of roughness greater than 180 micro inches are not permitted. Additionally, milling is not permitted if the crest to trough depth exceeds 0.001 inches (0.025 mm). A reasonable toleranceis allowed for both of these measurements. Non-conforming sandblasting or milling usually feels rough to the touch.
The requirement that the whole of the ‘impact area’ must be of the same material does not apply to clubs made of wood or putters (see Design of Clubs, Section 5f). The reason why it does not apply to wooden headed clubs is to allow the continued use of wooden clubs which have plastic inserts and brass screws in the center of the face. This design was commonly used in old persimmon woods, which may still be in use. However, a club face or insert made of a composite material would be considered to be of a single material, and therefore would not be contrary to this rule.
c. Impact Area Markings
All of the specifications for club face grooves are set out in Supplement A along with a complete guide as to the procedure for measuring width, depth and separation. For putters, see Design of Clubs, Section 5f.
(ii) Punch Marks
Punch marks may be used.
* The area of any such mark must not exceed 0.0044 square inches (2.84 sq.mm).
* A mark must not be closer to an adjacent mark than 0.168 inches (4.27 mm) measured from center to center.
* The depth of a punch mark must not exceed 0.040 inches (1.02 mm).
* If punch marks are used in combination with grooves, a punch mark must not be closer to a groove than 0.168 inches (4.27 mm), measured from center to center.
Punch marks are almost always circular in shape, and therefore the area of the punch mark can be determined using the calculation πr2 (where π=3.142). The radius of the punch mark (circle) can be found using the same magnifier that is used for measuring grooves (see Supplement A), as can the separation of two punch marks — measured center to center. The depth gauge used for measuring groove depths would not be suitable for measuring the depth of a punch mark. This measurement would require the use of a depth probe. While the depth of a punch mark is limited to 0.040 inches (1.02mm) within the Rules, it is highly unlikely that this measurement would ever be asked “in the field.”
If punch marks are used in combination with grooves, the following guidelines apply:
(iii) Groove/Punch Mark Combinations
* Small punch marks which are in line with a conforming groove, and which would be totally contained within a continuation of the groove, do not have to meet the punch mark to groove specifications. However, if the diameter of such punch marks exceeds the width of the groove, then they must meet the specifications.
* When measuring the center to center distance between a punch mark and the end of an in-line groove, the center of the groove is deemed to be half a groove width from the end edge of the groove.
Metal Wood Clubs
* Provided the following three conditions are satisfied, the preceding interpretation of the specifications for punch marks in line with a groove may also be granted for metal woods, even if the punch marks would not be totally contained by the continuation of the groove:
* there must be no more than three in-line punch marks in the part of the groove that is missing (i.e., in the gap between the ends of the partial grooves);
* the combined area of all of the in-line punch marks in any one such gap must not exceed the area of the missing groove; and
* the separation of the in-line punch marks from adjacent parallel grooves — measured from center to center — must be at least four times the width of the groove.
The following diagram illustrates each of the above conditions:
d. Decorative Markings
The center of the impact area may be indicated by a design within the boundary of a square whose sides are 0.375 inches (9.53 mm) in length. Such a design must not unduly influence the movement of the ball. Decorative markings are permitted outside the impact area.
The reason for this rule is to permit small, decorative logos in the center of the face or at the side of the ‘impact area.’ Non-conforming markings or logos that marginally encroach on the impact area may be permitted. However, markings outside the ‘impact area’ which are designed to influence the movement of the ball would be contrary to this rule.
e. Non-metallic Club Face Markings
The specifications regarding grooves, punch marks and decorative markings that are applicable to metal faces, or faces made from similarly hard materials, do not apply to faces made from other materials and whose loft angle is 24 degrees or less. However, any markings which could influence the movement of the ball are not permitted on such clubs.
Clubs with non-metallic faces and lofts that exceed 24 degrees may have grooves of maximum width of 0.040 inches (1.02mm) and a maximum depth of 1.5 times the groove width, but otherwise they must conform to the marking specifications above.
f. Putter Face
The specifications in Appendix II, 5, with regard to roughness, material and markings in the impact area, do not usually apply to putters.
However, if a groove in the face of a putter exceeds 0.035 inches in width and 0.020 inches in depth, the following guidelines apply:
• The width may not exceed 0.06 inches.
• The width to spacing ratio must be no less than 1:1.
• The depth must be less than the width, and may not exceed 0.04 inches.
• As for the grooves on irons and woods, the grooves on a putter must not have sharp edges.
Supplement A includes a complete guide regarding the procedure for measuring groove width, depth and separation.
Based on that look at b. and this should give you the answer...