Groove Measurement

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R&A Rules Limited

Measuring Clubface Markings and Determining Conformance

Revision 03-09

March, 2009

This document details the procedure for measuring the impact area marking on clubs (App II, 5c)

 DETERMINATION OF GROOVE CONFORMANCE
(Impact Area Markings (App II, 5c) Measurement Procedure)
Revision: 4th December 2008

This procedure describes the methods used to determine the conformance of impact area markings to the Rules from beyond 1st January 2010.

1. IMPACT AREA

The impact area on irons will be taken to be the entire extent of the face where a face treatment has been applied (for instance grooves, sandblasting etc.) or the central strip down the middle of the clubface having a width of 1.68” (42.67mm), whichever is greater.

From 1st January 2010 the impact area on drivers and fairway woods will be defined as the central strip down the middle of the clubface having a width of 1.68” (42.67mm)

Grooves and/or punch marks indicating a traditional impact area or any groove which encroaches into the impact area by less than 0.25” (6.35mm) will not be considered to be within the impact area and hence does not need to meet the specifications detailed in the following sections, unless they are designed to unduly influence the movement of the ball.

2. CALCULATION OF GROOVE PARAMETERS

2.1. Obtaining the Groove Profile

2.1.1. Ensure that the area to be measured is free from debris and paint/coatings.

2.1.2. For each club determine a line perpendicular to the grooves on the clubface where the groove trace is to be conducted. This location will be typically (but not restricted to) the centre of the impact area.

2.1.3. The profile should start and finish beyond the extreme grooves being measured.

2.1.4. The profile should include as many grooves as practical, without leaving the impact area appropriate for that club.

2.2. Measuring the Club Loft

The loft of the club will be determined using manufacturer’s specifications and/or markings or will be measured using a suitable gauge.

2.2.1. If there is doubt about whether a club loft is above or below 25 degrees then measure the loft of the club according to the Loft-Lie gauge measurement instructions. The top and bottom pins of the device shall be centred on the face height.

2.3. Measuring the Grooves from the Profile

For each groove in the measured groove profile:

figure 1

Figure 1

2.3.1. Using the 30° method of measurement (see Appendix A), identify the contact points on the groove and the adjacent grooves (if applicable). Determine the groove width (W) by measuring the distance between the marked 30° contact points.

2.3.2. Determine the spacing (S1 and S2) between adjacent grooves by measuring the distance of the land area between the 30° contact points identified in (2.3.1).

2.3.3. The adjacent land areas are joined by a line. Determine the groove depth (D) by measuring the perpendicular distance from the land area extension line down to the lowest point of the groove cross-section.

2.3.4. Determine the area (A) of each groove by measuring the area on the tracing that is bounded by the groove profile and the line connecting the adjacent land areas that was used to determine depth. Divide this value by the sum of the groove width (W) and the minimum adjacent spacing (S1 or S2) or, in the case of a top or bottom groove, the adjacent spacing.

3. DETERMINING THE CONFORMANCE OF IMPACT AREA MARKINGS

The following algorithm, along with the parameters measured in the previous section, will be used to determine the conformance of clubs to the Rules on impact area markings. 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% confidence as determined by standard Gauge R&R procedures. All measurements will include appropriate outlier controls to assure 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.

3.1. Groove Width

(applies to all clubs with the exception of putters)

3.1.1. If 50% or more of the measured groove widths exceed 0.035” (0.889mm) then the club is non-conforming.

3.1.2. If any single measured groove width exceeds 0.037” (0.940mm) then the club is non-conforming.

3.2. Groove Depth

(applies to all clubs with the exception of putters)

3.2.1. If 50% or more of the measured groove depths exceed 0.020” (0.508mm) then the club is non-conforming.

3.2.2. If any single measured groove depth exceeds 0.022” (0.559mm) then the club is non-conforming.

3.3. Groove Separation

(applies to all clubs with the exception of putters)

3.3.1. 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.

3.3.2. If any single measured groove separation is less than three times the maximum adjacent measured groove width minus 0.008” (0.203mm) then the club is nonconforming.

3.3.3. If 50% or more of the measured groove separations are less than 0.075” (1.905mm) then the club is non-conforming.

3.3.4. If any single measured groove separation is less than 0.073” (1.854mm) then the club is non-conforming.

Grooves must be designed and manufactured with the intent of being parallel throughout the impact area.

3.4. Groove Consistency

(applies to all clubs with the exception of putters)

3.4.1. The range of measured groove widths cannot exceed 0.010” (0.254mm).

3.4.2. The range of measured groove depths cannot exceed 0.010” (0.254mm).

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 requirements of 3.4.1 and/or 3.4.2 are satisfied.

3.5. Area over Width Plus Separation

(applies to all clubs with the exception of drivers and putters)

3.5.1. 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.

3.5.2. 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.

3.6. Edge Radius

(applies to all clubs with claimed, marked or measured lofts of 25 degrees or more)

Rounding of groove and punch mark edges shall be in the form of a radius having an effective radius not less than 0.010” (0.254mm) as determined by the two circles method described in Appendix B. The following two criteria are used for determining conformance:

3.6.1. 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.

3.6.2. If any single groove edge protrudes more than 0.0003” (0.0076mm) outside the outer circle (refer to Appendix B), then the club is non-conforming.

Refer to Appendix B for complete measurement details.

3.7. Punch Marks

(applies to all clubs with the exception of putters)

3.7.1. The area of punch marks must not exceed 0.0044 square inches (2.839 mm2).

3.7.2. The distance between adjacent punch marks (or between punch marks) and adjacent grooves must not be less than 0.168” (4.267mm), measured from centre to centre.

3.7.3. The depth of any punch mark must not exceed 0.040” (1.016mm).

3.7.4. For all clubs with the exception of driver and putters, the volume of punch marks in the impact area must not exceed the allowable for an equivalent groove (that is, 0.0030 in3 per square inch (0.0762 mm3/mm2) of impact area covered by punch marks).

3.7.5. For all clubs with claimed, marked or measured lofts of 25 degrees or more, 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.

3.7.6. For all clubs with claimed, marked or measured lofts of 25 degrees or more, If any single punch mark edge protrudes more than 0.0003” (0.0076mm) outside the outer circle (refer to Appendix B), then the club is non-conforming.

Appendix A
30° METHOD FOR MEASURING GROOVE WIDTH

1. SUMMARY

The method for measuring groove width using the 30° method is presented. It is generally understood that the groove in a club face starts where there is a significant departure from the plane of the face (land area). This method specifies where the measurement of the groove width should be taken when the edges of the grooves are rounded.

2. DESCRIPTION OF METHOD

The sidewall of a groove generally meets the face of the club (land area) with a filleted transition. The groove width measurement (W) is made between two points where a line, inclined at 30° to the land area of the club face, is tangent to the edge of the groove. This is shown in Figure 1.

figure a1

Figure A.1: Groove edge radius

If the tangent point using the 30° method occurs at a location that is more than 0.003” below the land area, then the width measurement shall be made at the points on the groove that are 0.003” below the land area. This is illustrated in Figure 2.

figure a2

Figure A.2: Maximum allowable deviation of the tangent point from the land area

APPENDIX B
METHOD FOR LIMITING THE SHARPNESS FO GROOVE AND PUNCH MARK EDGES

1. SUMMARY

The method for limiting the edge radius of grooves and punch marks is presented. This method provides three important features:

  • The edge radius limit is implicitly a function of the draught angle of the groove sidewall.
  • Allowances for manufacturing variability are incorporated.
  • The method is insensitive to small local variations in edge fillet radius

2. ANALYSIS OF GROOVE AND PUNCHMARK EDGE

The groove or punch mark sidewall meets the land area with a filleted transition. This is shown in Figure B.1.

figure b1

Figure B.1: Groove or punch mark edge radius

In order to determine whether such an edge is excessively sharp, a circle having a radius of 0.010” is drawn tangent to the groove sidewall and the adjacent land area. A second circle, concentric with the first and having a radius of 0.011” is drawn next. This arrangement is shown in Figure B.2.

figure b2

Figure B.2: Arrangement of concentric circles

By this method, a groove edge is deemed to be too sharp if any portion of the groove edge protrudes from the outer circle. The groove in Figure B.2 is such an example. The groove in Figure B.3, on the other hand, is not deemed to be too sharp, as the edge does not protrude from the outer circle.

figure b3

Figure B.3: Conforming groove edge

To be confident that the groove does in fact protrude from the outer circle and that this protrusion is not a measurement artefact or manufacturing abnormality, two additional criteria are provided for determining conformance.

2.1. Angular Extent of Protrusion from Outer Circle

Two lines are drawn from the centre of the concentric circles extending to the locations where the edge protrudes from the outer circle. The angle between these lines is the angle of protrusion as shown in Figure B.4. If the protrusion angle is greater than 10 degrees on fifty percent or more of the upper groove edges or lower groove edges or punch mark edges, the club is non-conforming

figure b4

Figure B.4: Maximum angular extent of edge protrusion

2.2. Maximum Protrusion

If any single edge protrudes from the outer circle by more than 0.0003” (measured as shown in Figure B.5) then the club is non-conforming.

figure b5

Figure B.5: Maximum protrusion