Tungsten Carbide Straight-Bore Dies

Precision carbide die blanks and straight-bore dies (直孔模具) for internal forming and pin guidance — the dimensional foundation of every cold heading die set.

Each tungsten carbide die starts as a sintered carbide die blank (carbide nib), selected by cobalt content to match the forming load, then finish ground inside and out. Straight bores support internal forming, sizing and punch guiding with consistent wall thickness and long wear life.

• Carbide die blanks — standard and custom nib sizes, grades YG6–YG15 and fine-grain options
• Straight-bore dies — ID and concentricity controlled within 0.01 mm
• Shells and housings — H13 or die steel cases, shrink-fitted for burst resistance

Why Tungsten Carbide for Cold Heading Dies

Tungsten carbide is the material a cold heading die lives or dies by. During heading, the bore wall takes millions of radial impact cycles at contact pressures that anneal and size ordinary tool steel. A hardened steel die may run tens of thousands of strokes before the bore grows out of tolerance; a properly selected tungsten carbide die holds its bore size for millions of strokes, which is why every serious cold heading die set uses a carbide nib inside a steel case.

The case is not a detail — it is what lets the carbide work. Carbide has enormous compressive strength but limited tensile strength, so the die blank is pressed into an H13 or die-steel shell with interference shrink fit. The shell keeps the carbide under permanent compression, and a bore that would crack as a free ring survives billions of impact cycles inside it.

Cemented Carbide and Hardmetal — Same Material, Different Names

Purchasing teams use three names for one material family. Tungsten carbide (WC) is the hard compound itself. Cemented carbide is the engineering material: tungsten carbide grains sintered in a cobalt metal binder, which is what our dies and blanks are actually made of. Hardmetal is the term used in European and ISO 513 literature for exactly the same cemented carbide family. If a drawing calls for hardmetal or cemented carbide tooling, a tungsten carbide die from our range is the correct part — we just grade it by cobalt content and grain size.

The cemented carbide we ship as standard sits at 14.1–15.0 g/cm³ density with hardness from 81.5 to 94.5 HRA across the grade range, transverse rupture strength well above tool steel, and thermal conductivity that pulls heading heat away from the working surface. That combination — extreme wear resistance plus real toughness — is what no steel or ceramic can match in a cold heading die.

Micrograin Tungsten Carbide

Grain size is the second lever after cobalt content. Micrograin tungsten carbide — carbide grain refined below roughly 0.8 μm — reaches the top of the hardness scale while keeping usable toughness, because fine grains force cracks to travel a longer, more interrupted path. In practice micrograin tungsten carbide grades such as KG03 (94.5 HRA at 4% Co) and UF03 (94.3 HRA) are the choice where the die must resist abrasive wear and still survive impact: small-diameter straight bores, sizing zones in multi-stage dies, and thin wear sections where a coarse-grain grade would chip.

Tungsten Carbide Grade Chart — Density, Hardness and Cobalt Content

We publish the full data sheet of our standard tungsten carbide material grades because grade selection should be an engineering decision, not a guess. Cobalt content is the main variable: less cobalt means higher hardness and wear resistance, more cobalt means higher toughness and impact resistance. Density falls and hardness falls as cobalt rises — the table makes the trade-off visible at a glance.

As a rule of thumb: grades in the 4–8% Co band (KG03, KG1, KG2, K100, UF03, WF05, WF08) are the hard, wear-resistant end of the range and suit sizing bores, wire drawing and abrasive service. The 10–15% Co band (WF10–WF40, KG3–KG7, TF25+, K200) trades a little hardness for the toughness that cold heading impact demands — this is where most of our cold heading die blanks are selected. The 18–25% Co grades (EA, VA and ST series) are impact grades for heavy upsetting and shrink-fit inserts under shock loading. Where both top hardness and impact survival are needed, the micrograin grades KG03 and UF03 are usually the answer. Send us the part and the work material and we will confirm the grade, not just quote it.

Tungsten Carbide Rod and Solid Carbide Rod Supply

Beyond finished dies we supply tungsten carbide rod and solid carbide rod for tool rooms that grind their own tooling. Rods come sintered (unground) or pre-ground, in the same tungsten carbide material grades as our die blanks, so a wear part machined from our rod matches the die it works with. Typical uses: punch rods, gauge pins, wear inserts, nozzles and rotary straightener parts.

Solid carbide rod is the right starting stock when the whole part works in the wear zone. Where only the working end takes the wear — as with most cold heading punches — a carbide head brazed onto an alloy steel shank gives the same life at a fraction of the material cost; see our brazed carbide cold heading punches and the solid cold heading punch and knock-out pin range.

Custom Tungsten Carbide Parts to Drawing

Most of what we ship is custom tungsten carbide parts made to customer drawing: straight-bore and shaped dies, punches and punch blanks, bushings, wear pads, straightener rolls and nozzles. The route from drawing to finished part is short because everything happens in-house: grade selection against the working load, powder pressing and HIP sintering, precision grinding of bore and outside diameter, and 100% dimensional inspection before packing.

Standard tolerances on ground straight bores are within 0.01 mm on ID with matching concentricity; special shapes are profile ground from your CAD file or from a sample part. If you are replacing an existing die, send the old one — we measure it, match or improve the grade, and quote from the measurement.

Frequently Asked Questions

Is cemented carbide the same as tungsten carbide?

Strictly speaking, tungsten carbide is the WC compound and cemented carbide (also sold as hardmetal) is tungsten carbide grains bonded with cobalt. In day-to-day trading the three names are used for the same material, and a “tungsten carbide die” is always a cemented carbide part.

Which tungsten carbide grade is best for a cold heading die?

For most cold and warm heading work, a 10–15% cobalt grade in the medium-fine grain range gives the best balance of bore-size retention and impact survival. Very abrasive work materials shift the choice toward 6–8% Co or micrograin grades; very heavy upsetting shifts it toward 15–25% Co. We confirm the grade from your part geometry and wire hardness.

Do you supply solid carbide rod from stock?

Yes. Common diameters of tungsten carbide rod are held in stock, both unground (sintered) and h6-ground, in standard lengths. Non-stock diameters and custom lengths are produced against order with the grade of your choice.

Can you produce custom tungsten carbide parts from a sample?

Yes. Send the sample or a dimensioned sketch; we measure it, propose a grade from the chart above, and quote with a delivery time, usually within one working day.

Tell us the bore, material and header model — we will recommend the right carbide grade. For the complete station, see our cold heading die sets and punch sleeves and tubing.