(The bracketed numbers refer to the corresponding paragraphs in Supplementary Paper B – “Guidance on the Measurement of Grooves on Club Faces”)
Clean club face [1]; ink the edges of ten grooves in a 5mm wide band. [2]
Check marking tool [1]; use it as described in full instructions [3] to scrape the edges of the inked grooves.
Use the magnifier to measure the width of all ten grooves, and record on the results sheet. [4, 5, 6, 7]
Calculate and record on the results sheet the average width, the greatest width and the width variation. [7]
Calculate and record the adjusted widths which allow for the uncertainties of measurement. [9]
Use the ruler to measure a span of ten grooves (e.g. from groove 1 to groove 11 (not 10), or 2 to 12). [8] {OR, if preferred, use the magnifier to measure a four groove span. [8]}
Calculate and record the average groove-to-groove pitch. [8]
Calculate and record the pitch to width ratio, remembering to use the adjusted width; also calculate the separation (pitch minus adjusted width).
Using quantities calculated in 5 and 8 above, answer the questions near the foot of the results sheet to determine whether the grooves conform. [10, 11] Manufacturers are advised to use actual widths in these calculations. [12]
Follow the steps on the results sheet to reach a decision on the club, if necessary repeating the measurement. [11]
NB. Consult the full instructions for grooves with inconsistent spacing, or other unusual features [12, 13, 14].