Guide
How Tight Must Milled Wedge Grooves Be to Stay Within the Groove Rules?
Milled wedge grooves are the parallel scoring lines cut into the face of a wedge, and the R&A and USGA equipment rules limit their width, depth, spacing, edge radius and consistency. This guide shows a supplier and a product manager how to set drawing tolerances inside that band and plan the measurement.
By Saola Manufacturing engineering team · Published · Updated
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Which groove limits matter for a milled wedge face?
Width, depth, separation, area-to-pitch ratio, edge radius and the consistency of width and depth all matter, and each is tested twice: once against a limit that most grooves must meet and once against a slightly looser limit that no single groove may exceed.
The R&A’s Supplementary Paper on 2010 face markings (read 2026) sets out the conformance algorithm, and the Part 2 text gives the headline limits of 0.035 in groove width, 0.020 in depth and a separation of at least three times the width and at least 0.075 in. The table reproduces the Supplementary Paper’s values for clubs other than driving clubs and putters; the paper states that they apply to clubs made on or after January 1, 2010, and Part 2 applies them to re-grooved clubs too.
Two points matter for a supplier. First, the edge radius requirement applies to lofts of 25 degrees and above, which includes most wedges. Second, the consistency requirement is not met just by staying under the limits: the paper says grooves must be designed and made to be symmetric, parallel and consistent, and that inconsistencies meant to influence the ball are not permitted even if the numbers pass. Putter faces are handled differently; see the separate guide on putter face milling pattern rules.
| Parameter | Majority test: non-conforming if | Single-value test: non-conforming if any | Notes |
|---|---|---|---|
| Groove width | More than 0.035 in (0.889 mm) | More than 0.037 in (0.940 mm) | Also measured for consistency, see below |
| Groove depth | More than 0.020 in (0.508 mm) | More than 0.022 in (0.559 mm) | Also measured for consistency, see below |
| Separation | Less than three times the maximum adjacent width, or less than 0.075 in (1.905 mm) | Less than three times the maximum adjacent width minus 0.008 in (0.203 mm), or less than 0.073 in (1.854 mm) | Edge to edge between adjacent grooves |
| Area / (width + separation) | More than 0.0030 in²/in (0.0762 mm²/mm) | More than 0.0032 in²/in (0.0813 mm²/mm) | Non-driving clubs |
| Edge radius (upper and lower edges) | Fails the two-circle test, with a 10 degree angular allowance | Any edge protrudes more than 0.0003 in (0.0076 mm) beyond the outer circle | Effective radius range 0.010 to 0.020 in (0.254 to 0.508 mm), lofts of 25 degrees and above |
| Width and depth consistency | Range of measured widths and range of measured depths must each not exceed 0.010 in (0.254 mm) | Not stated as a separate test in the extract read | Symmetric, parallel, consistent grooves are required by intent |
How are the groove limits tested, and what does 95 percent confidence mean for a supplier?
A measured value is judged on its dimensional measurement at no less than 95 percent confidence as determined by standard gauge R&R procedures, with outlier controls, so a supplier should plan on the instrument’s uncertainty counting against the margin.
The Supplementary Paper states that each dimensional measurement is based on at least 95 percent confidence as determined by standard Gauge R&R procedures, includes appropriate outlier controls so rulings are not based on anomalous data, and says that measurement techniques and their tolerances may be introduced at any time as they improve. It points to the R&A’s website for the full procedure and does not name an instrument in the pages read for this guide, so this guide does not either.
What follows for a drawing is simple even if the procedure is not. The table shows the derived headroom between the majority limit and the single-value limit; it is small, so a groove that sits at the upper edge of a drawing tolerance leaves almost no margin once instrument uncertainty is counted. The supplier’s gauge study should be run on the actual instrument and the groove geometry it will check; the acceptance logic is in the gauge R&R acceptance criteria guide.
| Parameter | Majority limit | Single-value limit | Derived headroom (single minus majority) |
|---|---|---|---|
| Width | 0.035 in | 0.037 in | 0.002 in (0.0508 mm) |
| Depth | 0.020 in | 0.022 in | 0.002 in (0.0508 mm) |
| Separation (absolute floor) | 0.075 in | 0.073 in | 0.002 in (0.0508 mm) |
| Area / (width + separation) | 0.0030 in²/in | 0.0032 in²/in | 0.0002 in²/in |
How should drawing tolerances be set inside the rule band?
Set each tolerance zone so that its worst-case limit is below the rule limit by at least the measurement uncertainty plus a process margin, and keep the width and depth ranges well below the consistency range limit.
Derived formula for an upper-limit feature such as width or depth: drawing upper limit = rule limit − U − M, where U is the expanded uncertainty from your gauge study and M is a process margin set by the capability you can demonstrate. For a lower-limit feature such as separation, add U and M instead. This is the author’s derivation, not wording from the rules, and the numbers have to come from the brand’s own gauge study and capability data.
For the consistency requirement, the paper limits the range of measured widths and the range of measured depths to 0.010 in each. A drawing tolerance on width of plus or minus T gives a range of 2T at most, plus tool wear across a run, so choose T and the cutter change interval together. For the edge radius, remember the two-circle test is not a plus-minus tolerance on a radius; ask the brand how it expects the edge profile to be called out and measured. Write the callouts in the language of ASME Y14.5-2018. The general reasoning on how much margin to allow is in the cost of tight tolerances guide.
What cutter-wear monitoring and sampling plan fits milled grooves?
Treat cutter wear as the main source of drift: set a tool-life limit by parts, measure a sample of grooves at the start and at fixed intervals, and keep the chart so a trend is seen before it reaches a limit.
A groove cutter wears at its corners, which widens the corner radius and changes the effective edge geometry before the width moves. That is why edge profile deserves its own check in addition to width and depth. A workable plan is a first-article measurement of every groove on one face after setup, a fixed-interval check of selected grooves on one face per tool-life block, and a full measurement after any tool change, offset change or fixture change.
Record each measurement and plot it against the drawing limit, not only pass or fail. The chart makes a drift visible while it is still inside the tolerance. Define the sample size, the grooves to be measured and the allowed uncertainty in the quality plan, and tie the first-article report to the inspection steps in the first article inspection guide. A coordinate measuring machine is common for inspecting dimensions and geometry on machined parts, as described in the CMM inspection guide, but confirm that the instrument resolves the smallest limit you need to verify.
What should the RFQ and the quality plan say, and what stays with the brand?
State the groove geometry as toleranced dimensions, the measurement method and the sample plan, and be explicit that conformance rulings and any measurement of record stay with the brand and the governing bodies.
Put the nominal and tolerance for width, depth, separation and edge condition on the drawing, name the measurement method and the sample plan, and say that the supplier reports data and does not certify conformance. A supplier can report measurements and hold a drawing; whether a wedge conforms is a ruling by the R&A and the USGA.
Heat treatment or a coating after milling changes the groove edge, so the measurement of record should be taken on the finished groove. Any such step on Saola work would be arranged through partner plants it manages and confirmed in the quote.
Can Saola mill wedge grooves?
Confirm it at drawing review: Saola's CNC milling at the lead plant is set up mainly for secondary machining of castings, and steel wedge heads are not among the substrates it lists, so groove milling on a wedge is not a standard job; finishes after milling would be arranged through managed partner plants.
See the CNC milling capability page and, for the post-milling finishes, the surface finishing page. Send the drawing, the groove tolerances, the sample plan and the annual quantity with the quote request.
Frequently asked
Is the 0.035 in width limit measured on the nominal groove or on each groove?
The paper tests measured values: a groove set is non-conforming if the majority test or the single-value test is triggered. Design to the limit with margin for the instrument.
Does the edge radius rule apply to every wedge?
The Supplementary Paper applies the effective radius requirement to lofts of 25 degrees and above. For lower lofts, the interpretation section gives a different treatment of doubtful edge cases.
Can I rely on the derived headroom table as a rule?
No. It is arithmetic on the published limits and is meant only to show how little room lies between the two tests.
Do these limits apply to putters?
No. Putters and driving clubs are excluded from the specifications in the paper that this guide uses, and the putter face has its own section in Part 2.
Does Saola certify groove conformance?
No. Saola reports measurements against the drawing; rulings belong to the governing bodies.
Sources
- Supplementary Paper C: 2010 Club Face Markings, R&A, specifications effective January 1, 2010, page read 2026
- Rules of Equipment, Part 2: Conformance of Clubs, section 2.5c, R&A, page read 2026
- Y14.5 Dimensioning and Tolerancing, ASME, Y14.5-2018 (R2024), page read 2026