Guides / Process

Designing a Tungsten Counterweight or Balance Weight

September 20, 2026 · Reviewed September 26, 2026

A counterweight or balance weight is one of the simplest reasons to choose tungsten: you have a fixed space and need to put as much mass in it as possible. This guide walks through the design decisions that affect how well a tungsten counterweight performs and how easily it gets machined and quoted.

Start from the envelope and the target mass

Most counterweight designs start backward from a typical part: the envelope is fixed by the surrounding assembly, and the goal is to hit a target mass within that space. Tungsten heavy alloy’s density, 17.0 to 18.5 g/cm³ depending on class, lets a given envelope carry more than twice the mass it would in steel and roughly 50% more than the same shape in lead. If your envelope is genuinely fixed and the mass target is tight, heavy alloy is usually the only material that gets you there without redesigning the surrounding assembly.

Work the math both ways: calculate what mass your envelope delivers at a given density, and separately calculate what envelope a target mass requires. If the two do not meet, either the class needs to move up (more tungsten content, more density) or the envelope needs a small increase.

Choosing between W-Ni-Fe and W-Ni-Cu

For most counterweights, W-Ni-Fe is the standard choice: it is the more common binder system, slightly more available, and its mild magnetism does not matter in a typical mechanical application like a crankshaft or rotor counterweight. W-Ni-Cu becomes necessary only when the part sits near equipment sensitive to magnetic fields, which is uncommon for counterweights but does occur in some instrumentation and aerospace applications. State the binder explicitly on your drawing either way, since a shop defaults to whichever is standard for them.

Mounting and attachment features

How the counterweight attaches to the assembly around it affects both function and machining cost.

• Through bolts and counterbores are routine to machine and are the simplest, most repeatable mounting method.
• Press fits and interference bores need tighter tolerance control, since heavy alloy’s stiffness behaves differently from a softer material like aluminum under press-fit stress.
• Balance holes or trim pockets, added after the main shape is roughed out, let the part be fine-tuned to a precise final mass or balance point without redesigning the whole piece.
• Keyways or flats, where the counterweight must not rotate relative to its shaft, machine the same way they would in steel, just with more tool wear.

Every feature removed for mounting also removes mass, so the design should account for that removed volume when calculating whether the part hits its target weight.

Tolerance: what actually needs to be tight

Counterweights are usually less tolerance-sensitive than shielding or precision instrument parts, but two things typically do need control: the mounting interface, since a loose or interference fit affects both function and safety in a rotating assembly, and the final mass, if the part is balancing a specific rotating system. Heavy alloy holds ±0.01 to ±0.025 mm on turned and milled features, which is more than sufficient for mounting bores and mating faces. Mass tolerance is usually expressed as a target weight with a plus or minus range, and shops trim to that with balance holes or a final light machining pass.

Repeat parts and near-net blanks

Counterweights are often produced in batches, whether for a production vehicle assembly, a repeated instrument design or aftermarket ballast. For batch quantities, ask your shop or sourcing contact whether a near-net sintered blank makes sense. It reduces the amount of expensive tungsten cut away as scrap, which matters more on counterweights than on many other part types because they are often bulkier, solid shapes rather than thin-walled components.

Specifying the part

A counterweight RFQ that gets quoted quickly includes:

1. Target mass or density, and the envelope dimensions if mass is the driving constraint.
2. Grade and binder, W-Ni-Fe unless there is a magnetic constraint.
3. Mounting features, dimensioned with tolerances on interfaces that matter.
4. Balance requirements, if the part goes into a rotating assembly.
5. Quantity, to determine whether a near-net blank is worth quoting.

When your drawing is ready, send your RFQ and we match it with shops that machine heavy alloy counterweights regularly. For the mechanics of how heavy alloy cuts, see tungsten heavy alloy machining. If price is the open question, see what drives the price of a machined tungsten part.

See also: tungsten counterweights and balance weights, for mass per envelope by class and how to set a mass tolerance.

Frequently asked questions

Sources

• Wikipedia - Tungsten heavy alloy
• Wikipedia - Tungsten

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• Grinding Tungsten Heavy Alloy: Which Wheel, What Finish, How Tight