Guides / Process

Common Mistakes When Specifying a Machined Tungsten Part

September 20, 2026 · Reviewed September 26, 2026

The parts that come back overpriced, delayed or unquotable almost always share the same handful of drawing and RFQ mistakes. None of them are complicated to fix once you know to look for them. This guide covers the most common ones.

Mistake 1: Writing “tungsten” without a grade

This is the single biggest source of delay on tungsten RFQs. Pure tungsten, tungsten heavy alloy and tungsten carbide are different materials with different processes, different tolerances and different costs, and a shop cannot quote accurately without knowing which one you mean. If heavy alloy, the ASTM B777 class and binder system (W-Ni-Fe or W-Ni-Cu) matter too. Fixing this is simple: name the exact grade on the drawing and in the RFQ, every time.

Mistake 2: Tolerancing every dimension tightly

A drawing where every dimension carries a ±0.01 mm tolerance, regardless of whether the feature affects fit or function, is more expensive to quote and more likely to be scrapped than a drawing that tolerances selectively. On tungsten this effect is larger than on steel, because inspection is slower and scrap material costs more. Reserve tight tolerances for features that actually mate, seal, align or bear load, and leave everything else at a general tolerance.

Mistake 3: Ignoring wall thickness and sharp corners on pure tungsten

Pure tungsten is brittle, and a drawing that treats it like a ductile metal, thin walls, sharp external corners, small deep holes, runs into cracking and chipping that a shop either flags before quoting or discovers during machining, both of which cost time. Walls thinner than about 1 mm, sharp corners without a chamfer or radius, and small deep holes are all warning signs on pure tungsten specifically. If your part needs these features, ask your shop whether the design can be adjusted, or whether the feature should shift to heavy alloy if the application allows it.

Mistake 4: Not stating the magnetic requirement

If a part must be non-magnetic, for example for use near MRI equipment or magnetically sensitive sensors, this has to be stated explicitly on the drawing. A shop defaults to whichever binder system is standard for them, usually W-Ni-Fe, which carries mild magnetism from its iron content. Discovering a magnetic requirement after the part is made means starting over in W-Ni-Cu.

Mistake 5: Leaving quantity and repeat volume out of the RFQ

Quantity affects whether a near-net sintered blank makes sense, and repeat volume affects whether tooling for that blank is worth the investment even if the first order is small. Leaving this information out means a shop quotes based on the smallest reasonable assumption, cutting from solid stock, which may not be the most cost-effective route if you actually expect to reorder.

Mistake 6: Skipping the material source question

Some buyers assume the shop always sources the tungsten blank, others assume they need to supply it themselves. Both are common arrangements, but the RFQ needs to say which one applies. A shop that assumes it is sourcing material, only to learn later that you expected to supply it, loses time reworking the quote.

Mistake 7: Requesting every possible test and certification by default

Material certification, density verification and radiographic inspection all add cost and lead time. Requesting all of them without checking what your application or customer actually requires inflates the quote unnecessarily. Match the testing request to the real requirement, not to a default checklist.

Mistake 8: Not distinguishing tungsten carbide from heavy alloy or pure tungsten

Carbide is a different material entirely, shaped by grinding and EDM rather than standard milling or turning. A drawing or RFQ for a carbide part sent to a shop set up for heavy alloy turning either gets no quote or an inflated one, since the shop cannot run the part the way it is specified. If your part is carbide, say so clearly so it reaches the right kind of shop from the start.

A quick pre-send checklist

1. Grade named explicitly, including class and binder system if heavy alloy.
2. Tolerances applied only to features that affect fit or function.
3. Thin walls and sharp corners reviewed if the part is pure tungsten.
4. Magnetic requirement stated, if applicable.
5. Quantity and expected repeat volume included.
6. Material source specified, shop-supplied or customer-supplied.
7. Testing and certification requirements matched to actual need.

Catching these before you send the RFQ is faster than catching them after a shop comes back with questions or an inflated quote. When your drawing is ready, send your RFQ and we match it with shops that cut your exact grade. For a full RFQ checklist, see how to write an RFQ for a machined tungsten part. For grade selection itself, see what each tungsten grade allows.

A consolidated list by grade is in our design for machining tungsten checklist.

Frequently asked questions

Sources

• Wikipedia - Engineering tolerance
• Wikipedia - Tungsten

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