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

(ii) Groove Depth

(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

NB: 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).