New Specifications and Interpretations
From 1 January 2010, the Rules on club face markings include the following three additional specifications for clubs other than driving clubs and putters:
As previously intimated (see Section 5c), these new specifications only affect new models of clubs manufactured on or after 1 January 2010 and competitions where the Groove and Punch Mark Condition is in use.
Interpretation of a Plain Groove
Based on all of the above, the following images are illustrative examples of permissible groove geometries:
Determining the Status of Markings in the Impact Area Against 2010 Specifications
Full details of the procedure for measuring club face markings and determining their status against the 2010 specifications can be found on The R&A’s website. However, a summary is as follows:
The following algorithm will be used to determine the conformance status of clubs to the new Rules on impact area markings from 1 January 2010, 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 stressed 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% confidence as determined by standard Gauge 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” (0.889 mm) then the club is non-conforming.
• If any single measured groove width exceeds 0.037” (0.940 mm) then the club is non-conforming.
(ii) Groove Depth
• If 50% or more of the measured groove depths exceed 0.020” (0.508 mm) then the club is non-conforming.
• If any single measured groove depth exceeds 0.022” (0.559 mm) then the club is non-conforming.
(iii) Groove Separation
(iv) Groove Consistency
Grooves must be designed and manufactured with the intent of being symmetric, parallel and consistent throughout the impact area. Consistency is interpreted to be:
Inconsistencies in the groove width, spacing or cross-section for the purpose of influencing the movement of the ball are not permitted, regardless of whether the above requirements are satisfied.
(v) Area over Width Plus Separation
(vi) Groove Edge Radius
Rounding of groove edges shall be in the form of a radius having an effective radius not less than 0.010” (0.254 mm) as determined by the two circles method, nor greater than 0.020” (0.508 mm). The following two criteria are used for determining conformance:
(vii) Punch Marks
As a result of the new Rule limiting the A/(W+S) of grooves, from 1 January 2010 the volume of punch marks in the impact area must not exceed the allowable value for an equivalent groove (that is, 0.0030 in3 per square inch (0.0762 mm3/mm2) of impact area covered by punch marks).