Guide
What Should a Golf Club Weight Screw Be Made Of: Steel, Aluminum or Tungsten?
A golf club weight screw is a threaded plug that fills a weight port in the sole or body of a club head and adds a known mass at a known place, so its material sets how much weight the port can carry and how the thread behaves over repeated adjustment. This guide is for product development managers specifying interchangeable weight screws and ports.
By Saola Manufacturing engineering team · Published · Updated
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Why does the material of a weight screw decide how much weight it adds?
Because the port is a fixed volume, the mass the screw adds is its density times that volume, so the material sets the range of weights a brand can offer in the same port. The table shows the densities of the three candidates.
A weight port is cut to a size the head can spare, and the screw fills it. Swap aluminum for stainless and the mass in the same volume rises by a factor of roughly three; swap stainless for a tungsten alloy and it rises by roughly another factor of two. Those ratios are derived from the densities in the table, which come from the Wikipedia article on aluminum (2.699 g/cm³ at 20 °C), the stainless steel article (7.5 to 8.0 g/cm³, depending on the alloy) and the tungsten alloy classes below.
The design question is therefore not which material is best but which set of materials gives the weight range the head design needs in the available port volume, with a screw that survives repeated adjustment. Do not ask a supplier to choose a material from a target head weight; ask for the screw masses you want and the volume you can offer.
| Material | Density (g/cm³) | Source | Mass of 1 cm³ (derived: density × 1 cm³) |
|---|---|---|---|
| Aluminum | 2.699 at 20 °C | Wikipedia, Aluminum | about 2.7 g |
| Stainless steel | 7.5 to 8.0 depending on the alloy | Wikipedia, Stainless steel | about 7.5 to 8.0 g |
| Tungsten heavy alloy, Class 1 to Class 4 | 16.85 to 18.85 across the four classes | GS Alloy listing of ASTM B777 | about 16.85 to 18.85 g |
| Pure tungsten | 19.254 at 20 °C | Wikipedia, Tungsten | about 19.25 g |
When is tungsten alloy the right material, and how should it be specified?
Tungsten alloy is the right material when the port volume is too small to reach the target mass with steel. Specify the class, the magnetic requirement and the mass tolerance on the finished piece, and treat the tungsten pieces as a managed input.
ASTM B777-15(2026) covers four classes of machinable, high-density tungsten base metal made by consolidating powder, for bare parts or parts with protective coatings, and its listed uses include weights and counter-balances. The page states that properties are verified on test coupons, not on finished parts, that some alloys can be weakly ferromagnetic, that freedom from magnetic response has to be specified in the purchase order, and that Class 4 is not available as a non-magnetic grade.
The table is a supplier’s listing of the class values, not the standard itself, and the density band within a class is a range: a screw of fixed shape will have a mass range, which is why the drawing should give a mass window for the finished piece, not just a class. This guide does not assign a class to a head weight, because no source read for it does. Tungsten pieces, whether press-fitted, bonded or threaded into a steel screw body, are a bought-in input that is not made at a CNC lathe; who supplies them is confirmed in the quote.
Weighing is the acceptance method that matters, so state the mass tolerance in grams, the sampling plan and the balance resolution on the drawing or in the RFQ. If the head uses a magnetic sensor, a fitting station or a magnetic fixture, state the magnetic requirement as well.
| Class | Nominal tungsten (weight %) | Density (g/cm³) | Hardness (Rockwell C, max) | Magnetic grade offered |
|---|---|---|---|---|
| Class 1 | 90 | 16.85 to 17.25 | 32 | Non-magnetic or magnetic |
| Class 2 | 92.5 | 17.15 to 17.85 | 33 | Non-magnetic or magnetic |
| Class 3 | 95 | 17.75 to 18.35 | 34 | Non-magnetic or magnetic |
| Class 4 | 97 | 18.25 to 18.85 | 35 | Magnetic only |
How do galling, thread locking and coatings affect the screw and the port?
Stainless-on-stainless threads are prone to galling, and a threadlocker has to be chosen to hold on the plated, passive or coated surfaces a weight port may have. Decide the pairing and the locker before the thread tolerance is frozen.
The Wikipedia article on galling says galling often occurs in screws and bolts, that stainless steel is particularly susceptible because of its protective oxide layer, and that harder materials, lubrication or a different pairing reduce it; the stainless steel article says austenitic fasteners are particularly susceptible and that pairing with a different metal or grade helps. The stainless steel thread galling guide covers the machining side, and galling in aluminum and titanium threads covers the soft-metal case.
For a locker, the Henkel Loctite 243 technical data sheet (November 2020) describes a medium-strength anaerobic threadlocker designed for fasteners that need normal disassembly with standard hand tools, says it works on passive substrates such as stainless steel and plated surfaces, offers an activator to speed cure, and says it is not normally recommended on plastics. That is the right shape of product for a screw that is removed with a wrench; it is not a recommendation for your design, so run a torque-retention trial on your actual screw and port.
If the port is anodized, the thread dimensions change and the surface changes; the threads after anodizing and plating guide explains the allowance. Anodizing is arranged through a partner plant that Saola manages, so the drawing should say whether the thread is masked or coated.
What does Rule 2 require of an adjustable weight system?
Rule 2 allows weight adjustment features on all clubs, but the adjustment must need a special tool, the parts must be firmly fixed with no reasonable likelihood of working loose during a round, and every configuration must conform.
The R&A’s Part 2 text (read 2026) states that the adjustment must not be made just by using the fingers, and gives an Allen key, a Phillips screwdriver or a custom-made device as examples of a special tool. It also says the adjustable parts must be firmly fixed, that where a screw fixes the mechanism the club must be unusable without the screw, and that every configuration of adjustment must conform.
For a screw designer this means the drive feature, the thread and the retention are part of conformance, not only of assembly. A drive that can be turned by hand, a screw that can back out and leave the club usable, or a weight that moves the head outside a limit in one setting are all drawing and design decisions for the brand. Conformance rulings stay with the governing bodies.
What belongs on the drawing and in the RFQ for weight screws and ports?
Give the material by designation, the finished mass window, the thread with its tolerance class and engagement length, the drive feature, the surface treatment and the threadlocker, and ask for a first-article report that includes mass and torque-retention data.
Define the port and the screw together: port thread and depth, screw thread and length, seat face, drive and any retention feature. The thread depth and engagement length rules in the thread engagement length guide apply to small screws in thin head walls, where the engagement is often the limiting factor.
In the RFQ, send the annual quantity, the mass windows, the finish route (for example anodize or plating, arranged through partner plants), and the inspection plan. Ask the supplier to report the mass of a sample of each lot with a stated balance, the thread gauge result and the removal torque after the locker has cured.
Can Saola make the screws and the ports?
Small turned screws in the bar materials listed on the CNC turning page, such as 6061-T6 or 2011-T3 aluminum and free-machining steel, are routine work at the lead CNC plant; stainless or tungsten screws and ports in a cast club head are not listed materials, so confirm them at drawing review.
See the CNC turning capability page and the CNC milling capability page. Anodizing and plating are arranged through partner plants that Saola manages. Send the drawing with the quote request.
Frequently asked
Is a tungsten weight screw always better than a steel one?
No. Tungsten alloy adds more mass in the same volume, but it is a managed input with its own class, magnetic and coating decisions. Use it when steel cannot reach the target mass in the available port.
Does ASTM B777 tell me which class to use for a given club weight?
No. The standard defines classes and properties. Choosing a class for a head weight is a design decision based on the port volume and the mass target.
Can a weight screw be turned by hand on a conforming club?
The R&A text says adjustment must need a special tool and must not be possible just by using the fingers, so a hand-turned screw is a conformance risk for the brand to assess.
Does thread locker work on stainless steel screws?
The Loctite 243 data sheet says the product works on passive substrates such as stainless steel and plated surfaces, and that an activator can speed cure. Test your own screw and port before specifying it.
Does Saola test weight screws for rule conformance?
No. Saola makes and measures parts to the drawing. Rulings belong to the governing bodies.
Sources
- Rules of Equipment, Part 2: Conformance of Clubs, R&A, page read 2026
- ASTM B777-15(2026), Standard Specification for Tungsten Base, High-Density Metal, ASTM International, store page read 2026
- ASTM B777 Tungsten High-Density Metal, GS Alloy product listing, read 2026
- LOCTITE 243 Technical Data Sheet, Henkel, November 2020
- Aluminum (element), Wikipedia, page read 2026
- Tungsten, Wikipedia, page read 2026
- Stainless steel, Wikipedia, page read 2026
- Galling, Wikipedia, page read 2026