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How to Source Machined Tungsten Shielding and Counterweights

September 25, 2026 · Reviewed September 26, 2026

Shielding parts and counterweights are the two most common reasons a buyer sources machined tungsten in the first place, and they share enough in common that this guide covers both together. Both start from the same material decision and the same blank strategy, and diverge only in which tolerances actually matter.

Why tungsten instead of lead or steel

Tungsten heavy alloy runs 17.0 to 18.5 g/cm³, roughly 50 to 60% denser than lead and more than twice as dense as steel. For a shielding part, that means the same attenuation in a smaller, lighter package. For a counterweight, it means more mass in a fixed mounting envelope than steel or lead could provide.

Density is not the only reason. Lead is soft and does not hold a machined feature well, and it carries handling and regulatory concerns that heavy alloy does not. Steel is easy to machine but cannot match tungsten’s density, so a steel part built to the same mass would simply be too large for many shielding and counterweight applications. Heavy alloy machines on standard CNC equipment, closer in behavior to hard cast iron than to a difficult exotic metal, which is what makes it practical rather than just theoretically superior.

Specifying the grade

Most shielding and counterweight parts use W-Ni-Fe heavy alloy, the standard binder system. Where the part sits near MRI equipment, magnetic sensors or anything sensitive to stray fields, W-Ni-Cu removes the mild magnetism that W-Ni-Fe carries, at a similar density.

The ASTM B777 class depends on how much density your application needs against how much the part is allowed to weigh. If you know your target density or mass, that is enough information for a shop or mill to recommend a class; you do not need to already know the class number before you send an RFQ.

Shielding parts: collimators, inserts and containers

Shielding parts add a functional-geometry layer on top of the material decision:

Wall thickness has to provide enough shielding mass without unnecessary bulk, sized to the actual radiation energy and required attenuation for your application.
Aperture size and alignment, on parts like collimators, are usually the tightest-toleranced features, since they directly determine what passes through the shield.
Void and inclusion checks matter more on shielding parts than on most machined parts, since an internal void reduces effective shielding thickness at that point. Radiographic inspection catches this when it matters.
Surface finish is rarely a tight requirement on shielding parts unless the part also serves as a mounting or sealing surface.

Counterweights and balance weights

Counterweights shift the emphasis from internal geometry to mass and mounting:

Mass tolerance is often expressed as a target weight with a defined range, and parts are trimmed to it with a final light machining pass or drilled balance holes, separate from the part’s dimensional tolerances.
Mounting interfaces, bolt holes, counterbores or press fits, need the same tolerance control as any structural mechanical interface, machined the same way they would be in any dense metal.
Coatings or platings are sometimes specified for corrosion protection or appearance, though heavy alloy does not need a coating for corrosion resistance the way steel often does; confirm whether a finish is actually functional or cosmetic before adding cost for it.
Fasteners, if the counterweight itself is threaded or uses tungsten hardware, follow the same threading guidance as any other heavy alloy feature: routine in larger sizes, more care needed on fine threads.

Blank options

For low quantities, shielding parts and counterweights are usually machined from standard heavy alloy bar or plate stock. For quantities in the dozens and above, a near-net sintered blank, pressed close to the final shape, cuts down the amount of expensive material removed as scrap. The tradeoff is upfront pressing tooling cost, which pays back faster on larger, bulkier parts like counterweights than it might on a thin, simple shielding insert. Tell your shop your expected quantity and repeat volume so they can tell you whether a near-net blank is worth quoting.

Tests and paperwork

Shielding and counterweight parts for regulated or safety-related applications, medical, aerospace, industrial radiography, commonly call for:

Material certification referencing ASTM B777, traceable to a specific heat or lot.
Density verification, confirming the finished part meets its density specification, especially important on shielding parts where density is directly tied to function.
Dimensional inspection reports, particularly for the tolerances that matter most: apertures on shielding parts, mounting interfaces and mass on counterweights.
Radiographic inspection, when internal void-free integrity is a requirement rather than a nice-to-have.

Ask only for what your application or customer actually requires. Each additional test adds cost and a few days of lead time, and requesting a full battery of tests by default inflates quotes without adding real value on parts that do not need it.

What to put in the RFQ

Part type: shielding insert, collimator, container, counterweight or balance weight.
Grade and binder: W-Ni-Fe unless there is a magnetic constraint, ASTM B777 class or target density.
Critical dimensions and tolerances: aperture size and alignment for shielding, mounting interface and mass target for counterweights.
Quantity and expected repeat volume, to judge whether a near-net blank makes sense.
Certification and testing requirements, stated explicitly rather than left to assumption.
Material source: shop-supplied blank or customer-supplied material.

When your drawing is ready, send your RFQ and we match it with up to three shops experienced in shielding and counterweight work. For what drives the price across all of this, see what machined tungsten parts cost. For the grade decision itself, see pure tungsten versus heavy alloy versus carbide.

Frequently asked questions

What is the difference between sourcing a shielding part and a counterweight?

Both are usually the same material, tungsten heavy alloy, and machine the same way. The difference is which tolerance matters most: shielding parts are toleranced around apertures, wall thickness and alignment, while counterweights are toleranced around mounting interfaces and final mass.

Do I need to specify an ASTM B777 class, or is a density target enough?

A density target is enough to start. If you know the class, state it; if you only know the density or mass you need, tell your shop or sourcing contact that instead and let them recommend a class that meets it.

How long does it take to source a machined shielding part or counterweight?

It depends on grade, blank type and testing. Parts cut from standard heavy alloy bar stock with no special certification move fastest. Parts needing a near-net blank or radiographic inspection take longer. Confirm a real lead time with the shop once you are matched, since it depends on their current schedule too.

Sources

Need a quote for this part?

Send the drawing. We match you with up to 3 shops that cut your tungsten grade and reply within 24 business hours.

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