Equipment Rules

This publication contains guidelines to help manufacturers, rules officials and other interested parties interpret the Rules relating to the design and manufacture of golf clubs and balls, as set forth in Appendices II and III of "The Rules of Golf."

Similar to the Rules, these guidelines will be continually reviewed, and modifications may be made in the future. The principles and philosophies expressed within this publication are held by both the United States Golf Association and R&A Rules Limited ("The R&A").

 

 

 

 

 

 

 

Browse the 2012-2015 Rules

Supplement D

Determining the Conformance Status of Grooves in the Impact Area Effective January 1, 2010

The following algorithm will be used to determine the conformance of clubs to the new Rules on impact area markings, regardless of what method has been used to obtain the measurements.Within the following procedure, the inherent difficulty of manufacturing grooves has been taken into consideration.However, it should be noted that clubs must be designed and manufactured with the intent of conforming to the Rules.

Note that for all dimensional limitations described below, each measurement will be based on a confidence level of at least 95% as determined by standard Gage R&R procedures. All measurements will include appropriate outlier controls to ensure that rulings are not based on spurious or anomalous data. Improvements to measurement techniques and, consequently, the associated measurement tolerances may be introduced at any time.

(i) Groove Width

  • If 50% or more of the measured groove widths exceed 0.035 inches (0.889 mm), then the club is non-conforming.
  • If any single measured groove width exceeds 0.037 inches (0.940 mm), then the club is non-conforming.

(ii) Groove Depth

  • If 50% or more of the measured groove depths exceed 0.020 inches (0.508 mm), then the club is non-conforming.
  • If any single measured groove depth exceeds 0.022 inches (0.559 mm), then the club is non-conforming.

(iii) Groove Separation

  • If 50% or more of the measured groove separations are less than three times the maximum adjacent measured groove width, then the club is non-conforming.
  • If any single measured groove separation is less than three times the maximum adjacent measured groove width minus 0.008 inches (0.203 mm), then the club is non-conforming.
  • If 50% or more of the measured groove separations are less than 0.075 inches (1.905 mm), then the club is non-conforming.
  • If any single measured groove separation is less than 0.073 inches (1.854 mm), then the club is non-conforming.

(iv) Groove Consistency

  • The range of measured groove widths cannot exceed 0.010 inches (0.254 mm).
  • The range of measured groove depths cannot exceed 0.010 inches (0.254 mm).

Inconsistencies in the groove width, spacing or cross-section for the purpose of unduly influencing the movement of the ball are not permitted, regardless of whether the above requirements are satisfied.

(v) Area over Width Plus Separation

  • If 50% or more of the measured values of A/(W+S) are greater than 0.0030 in2/in (0.0762 mm2/mm), then the club is non-conforming.
  • If the measured value of A/(W+S) value for any single groove is greater than 0.0032 in2/in (0.0813 mm2/mm), then the club is non-conforming.

(vi) Groove Edge Radius

Rounding of groove and punch mark edges shall be in the form of a radius having an effective radius not less than 0.010 inches as determined by the two circles method described in Appendix C of the Test Protocol.The following two criteria are used for determining conformance:

  • If 50% or more of the upper groove edges or 50% or more of the lower groove edges fail the two circles method subject to a 10 degree angular allowance, then the club is non-conforming.
  • If any single groove edge protrudes more than 0.0003 inches (0.0076 mm) outside the outer circle (refer to Appendix C of the Test Protocol), then the club is non-conforming.

(vii) Punch Marks

  • If 50% or more of the punch mark edges fail the two circles method subject to a 10 degree angular allowance, then the club is non-conforming.
  • If any single punch mark edge protrudes more than 0.0003 inches (0.0076 mm) outside the outer circle (refer to Appendix C of the Test Protocol), then the club is non-conforming.

Note: For all clubs other than drivers and putters, the volume of punch marks in the impact area must not exceed the allowable area over width plus separation for an equivalent groove (i.e., 0.0030 in3/in2 per square inch of impact area covered by punch marks).

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