R&A Rules LimitedandUnited States Golf Association

PROTOCOL FOR MEASURING IMPACT AREA MARKINGS
OF GOLF CLUBS

TPX3001Rev. 2.0
1 December 2020

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Revision

DateDetails

1.0

Dec-2008

Reference to ‘hybrids’ removed from paragraph two.
The impact area of a hybrid club will be determined on acase by case basis.

1.1

Dec-2009

Various updates including units (from 0.0030” to 0.0030
in2/in), clarification that grooves must be parallel
throughout the impact area, that 3.7.4 do not apply toputters and drivers and that 3.7.5 and 3.7.6 only applies
to clubs with claimed, marked or measured lofts of 25
degrees or greater.

1.2Mar-2009

Inserted reference to outlier control for removal ofanomalies and spurious measurements. Clarified thatinconsistencies in groove width, spacing or cross-section
with the intent to unduly influence the movement of theball are not permitted.

2.0

1-Dec-2020

Updated references to The Equipment Rules.
Reformatted step numbering and section titles to beconsistent with other protocols.

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1 Scope
This protocol describes the method used to determine the conformance of impact area
markings to the Equipment Rules, Part 2, Section 5 (c), as administered by R&A Rules Ltd(The R&A) and the United States Golf Association (USGA).

2 Test Protocol
2.1 Calculation of groove parameters
a. Ensure that the area to be measured is free from debris. Any paint/coating on the faceor in the impact area markings may be removed.
b. Measure the groove profilei.
The profile shall be measured in an orientation which is perpendicular to thegrooves on the club face.
ii.
The profile should include as many grooves as practical within the impact area.
c. Determine the edge points of the grooves;i.
The edge points of a groove are defined as the point where a line, inclined at30° to the land area of the club face, is tangent to the edge of the groove (Figure1)
30°
land area

W30°
groove edge

Figure 1:The 30° method for determining the edge points of a groove.

ii.

If the edge point defined using the 30° method occurs at a location that is morethan 0.003 in. (0.0762 mm) below the land area, then the edge points shall bethe points on the groove that are 0.003 in. (0.0762 mm) below the land area
d. Calculate the groove width (W), separation (S1 and S2), depth (D) and area (A) of eachgroove from the groove profile (Figure 2)i.
The groove width is the distance between the edge points of the groove.
ii.
The groove separation is the distance of the land area between the edge pointsof adjacent grooves.
iii.
The groove depth is the perpendicular distance between an extension of theland area and the lowest point of the groove profile.
iv.
The area of the groove is the area bounded by the groove profile and the line
connecting the edge points.

Figure 2: Groove parameters to be measured from the groove profile.

e. For each groove, calculate A/(W+S), Area divided by (Width plus Separation), using
the smaller of the adjacent separation values for that groove.

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f.

Calculate the sharpness of the groove edges, on both sides of the groove (upper andlower), using the two circles methodi.
A circle having a radius of 0.010 in. (0.254 mm) is drawn tangent to thesidewall and the adjacent land area. A second circle, concentric with the firstand having a radius of 0.011 in. (0.2794 mm) is also drawn (Figure).

Figure 3: Arrangement of concentric circles.

ii.

If the edge does not protrude from the outer circle (Figure 4), then the edge
radius is conforming.

Figure 4: Edge does not protrude from outer circle.

iii.

If the edge protrudes from the outer circle, two lines are drawn from thecentre of the concentric circles extending to the locations where the edge
protrudes from the outer circle. The angle between these lines is the angle ofprotrusion (Figure 5).

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Figure 5: Maximum angular extent of edge protrusion determined by the angle of protrusion

Note. The same method for determining edge sharpness is also utilised for the evaluation of
the sharpness of the edges of punch marks.

3 Determination of conformance statusa. Groove Widthi.
If 50% or more of the measured groove widths exceed 0.035 in. (0.889 mm)then the club is non-conforming.
ii.
If any single measured groove width exceeds 0.037 in. (0.940 mm) then theclub is non-conforming.
b. Groove Depthi.
If 50% or more of the measured groove depths exceed 0.020 in. (0.508 mm)then the club is non-conforming.
ii.
If any single measured groove depth exceeds 0.022 in. (0.559 mm) then theclub is non-conforming.
c. Groove Separationi.
If 50% or more of the measured groove separations are less than three times
the maximum adjacent measured groove width, then the club is nonconforming.
ii.
If any single measured groove separation is less than three times the maximumadjacent measured groove width minus 0.008 in. (0.203 mm) then the club isnon-conforming.
iii.
If 50% or more of the measured groove separations are less than 0.075 in.
(1.905 mm) then the club is non-conforming.
iv.
If any single measured groove separation is less than 0.073 in. (1.854 mm)then the club is non-conforming.
d. Groove Consistencyi.
If the range of measured groove widths exceeds 0.010 in. (0.254 mm) then theclub is non-conforming.
ii.
If the range of measured groove depths exceeds 0.010 in. (0.254 mm) then theclub is non-conforming.
e. Area over Width Plus Separation (applies to all clubs except for drivers)i.
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.
ii.
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.

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f.

Edge Radius (applies to all clubs with claimed, marked or measured lofts of 25 degreesor higher)i.
If 50% or more of the upper groove edges or 50% or more of the lower grooveedges have an angle of protrusion greater than 10°, then the club is nonconforming.
ii.
If any single groove edge protrudes more than 0.0003 in. (0.0076 mm) outside
the outer circle, then the club is non-conforming.
g. Punch Marksi.
If the maximum dimension of any single punch mark exceeds 0.075 in (1.905mm), then the club is non-conforming.
ii.
If the distance between any adjacent punch marks (or between any punchmarks and an adjacent groove) is less than 0.168 in. (4.267 mm), measured
from centre to centre then the club is non-conforming.
iii.
If the depth of any punch mark exceeds 0.040 in. (1.016 mm) then the club isnon-conforming.
iv.
For all clubs with the exception of driver, if the volume of punch marks in theimpact area exceeds the allowable for an equivalent groove (that is, 0.0030
in3/in2 (0.0762 mm3/mm2) of impact area covered by punch marks) then theclub is non-conforming.
v.
For all clubs with claimed, marked or measured lofts of 25 degrees or higher, if
50% or more of the punch mark edges have an angle of protrusion greater than10°, then the club is non-conforming.
vi.
For all clubs with claimed, marked, or measured lofts of 25 degrees or greater,
if any single punch mark edge protrudes more than 0.0003 in. (0.0076 mm)outside the outer circle, then the club is non-conforming.

The profiles will be used to assess the requirements that the grooves must have a symmetricalcross-section, have sides which do not converge and in the case of clubheads with loft angle
greater than or equal to 25 degrees, have a plain cross-section.
Note: All measurements will include appropriate outlier controls. Screening methods may be
employed as appropriate.

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