Guides / Process

Tungsten Heavy Alloy Machining: What to Expect From a Shop

September 20, 2026 · Reviewed September 26, 2026

Tungsten heavy alloy is the material most machine shops mean when a buyer asks for “machined tungsten.” It is 90 to 97% tungsten held together by a nickel-iron or nickel-copper binder, and that binder is what makes it practical to cut. This guide covers how heavy alloy actually machines, what shops watch for, and what to put on a drawing so a quote comes back accurate.

Why heavy alloy machines easily and pure tungsten does not

Pure tungsten is brittle at room temperature, which makes it prone to chipping and cracking under a cutting tool. The nickel-iron or nickel-copper binder in heavy alloy changes that behavior. It gives the material enough ductility to shear cleanly under a cutting edge instead of fracturing, which is why shops compare heavy alloy to hard cast iron rather than to a difficult ceramic-like material.

That single property, ductility from the binder, is why heavy alloy covers most of the machined tungsten market: shielding, balance weights, counterweights and ballast, where the application calls for density and toughness rather than the extreme heat resistance of pure tungsten.

Turning, milling, drilling and tapping

Heavy alloy responds to the same operations as any other metal:

• Turning produces short, manageable chips at moderate speeds. Diameters and lengths that would be routine in steel are routine in heavy alloy too, with allowance for the extra weight when chucking long or heavy blanks.
• Milling removes material cleanly with carbide end mills. Pocket features, flats and profiles hold a good surface finish without special tooling.
• Drilling and tapping work on standard equipment. Deep, small-diameter holes need the same care they would in any dense metal: pecking cycles, coolant and rigid tooling to avoid deflection.
• Threading is routine on external and internal features, cut or tapped depending on size and tolerance.

None of these operations require exotic machines. What they require is a shop that has cut the material before and knows how it differs from steel in practice.

What actually changes versus cutting steel

Four things separate heavy alloy from a steel job on the same machine.

Tool wear. The tungsten grains in the microstructure are abrasive. Carbide inserts and end mills that would run for hours in steel need replacing sooner in heavy alloy. Shops account for this in their quotes; it is one reason heavy alloy machining costs more than steel machining of the same geometry.

Part weight. A heavy alloy part weighs more than twice the same shape in steel, because the material is roughly 17.0 to 18.5 g/cm³ versus 7.85 g/cm³ for steel. Workholding, lifting and fixture design all have to account for that. A thin-walled part that would sit safely on a steel fixture can shift or drop when it is heavy alloy.

Magnetism. W-Ni-Fe grades carry mild magnetism from the iron content. For most applications this is irrelevant. For parts used near MRI equipment, sensors or anything sensitive to stray magnetic fields, the drawing should call out W-Ni-Cu instead, which uses copper in place of iron and is effectively non-magnetic.

Chip handling. Heavy alloy chips have scrap value and shops usually collect them separately from steel and aluminum chips. This does not affect the buyer directly, but it is one more reason not every general machine shop takes on tungsten work.

Tolerances and finish you can plan around

On turned and milled heavy alloy parts, ±0.01 to ±0.025 mm is common across most features. Bores, threads and O-ring grooves are routine at these tolerances. Where a feature needs to be tighter, for example a mating face or a bearing bore, shops finish it by grinding after the main machining operations.

Surface finish out of the mill or lathe is typically comparable to steel machined under similar conditions. A specified finish tighter than the part needs adds cost without adding function, the same rule that applies to any metal.

Features that add cost or risk

A handful of design choices decide whether a heavy alloy part is straightforward or expensive to quote.

Feature	Effect on heavy alloy machining
Thin walls	Possible with care, but weight and rigidity matter more than in steel
Long, small-diameter bores	Slower to drill and ream, deflection risk
Tight flatness on large faces	Often finished by grinding after milling
Non-magnetic requirement	Must be specified (W-Ni-Cu), cannot be assumed
High-volume repeat parts	Worth asking about a near-net sintered blank

Near-net blanks versus cutting from solid

Because heavy alloy is expensive per kilogram, the starting blank matters more here than it does with steel. For one-off or low-quantity parts, shops usually machine from standard bar or plate stock. For quantities in the dozens and above, a mill can press and sinter a blank close to the finished shape, leaving only a few millimeters to machine. That reduces material waste, machine time and tool wear, and on the right part it pays back the tooling cost quickly. Ask your shop, or the sourcing service matching you, whether your quantity justifies it.

What to put on the RFQ

A heavy alloy RFQ that gets an accurate quote on the first pass includes:

1. The class, referencing ASTM B777 if you know it, or the density range you need.
2. W-Ni-Fe or W-Ni-Cu, stated explicitly if magnetism matters.
3. A STEP file and dimensioned drawing with tolerances called out on the features that matter, not on every dimension.
4. Quantity and expected repeat volume, so the shop can judge whether a near-net blank is worth quoting.
5. Any required certs or tests, such as material certification or density verification.

If you already have a drawing ready, send your RFQ and we match it with up to three shops that cut heavy alloy at your size and class. For the broader question of what pure tungsten allows that heavy alloy does not, see what each tungsten grade is capable of. If price is the open question, what machined tungsten parts cost breaks down the drivers.

For pure tungsten, tungsten copper and the rest of the process, see our guide on how to machine tungsten.

See also: 95% tungsten heavy alloy (ASTM B777 Class 3), for the class limits and typical mill values.

Frequently asked questions

Sources

• Wikipedia - Tungsten heavy alloy
• ASTM B777 - Standard Specification for Tungsten Base, High-Density Metal

Keep reading

• Thin Tungsten Plate and Foil: How Shops Machine It Without Cracks or Warp
• Grinding Tungsten Heavy Alloy: Which Wheel, What Finish, How Tight