The Difference Between High Speed and Tungsten Steel
Both are cutting-tool materials, and both get called steel on the shop floor. They are not the same family. This page compares high speed and tungsten steel on hardness, hot hardness and failure mode, so you can pick the right tool for a job and stop burning cutters on the wrong material.
High speed and tungsten steel at a glance
Typical values for a 10 mm end mill in P-class steel. Your numbers move with coating and geometry.
| Property | High speed steel (HSS) | Tungsten carbide |
|---|---|---|
| Hardness at room temp | HRC 62–66 | HRA 89–93 (≈ HRC 70+) |
| Hot hardness limit | About 600 °C | About 1,000 °C |
| Cutting speed in P steel | 25–40 m/min | 120–250 m/min |
| Toughness under shock | High, forgives chatter | Low, chips on impact |
| Typical tool cost | Low per cutter | Higher per cutter |
| Regrind life | Many regrinds possible | Fewer, diamond wheel needed |
| Best for | Taps, reamers, small drills | Milling, turning, high volume |
| Worst for | High-speed production | Interrupted cuts on hard stock |
Which tool for which operation
Use this when the drawing and the machine are already fixed.
| Operation | First choice | Why |
|---|---|---|
| Face milling a 4140 block | Carbide insert | Speed pays off on long passes |
| Hand tapping M6 in 304 | HSS tap | Toughness survives torque reversal |
| Reaming a Ø8 H7 bore | HSS reamer | Cheaper to regrind, stable size |
| Roughing a casting with scale | HSS or coated carbide | Scale chips an unprotected edge |
| Turning 10,000 small pins | Coated carbide | Cycle time dominates part cost |
| Drilling deep holes Ø3 in Inconel | Carbide drill | HSS would work-harden the wall |
| Cutting a keyway by hand | HSS broach | Manual feed needs forgiveness |
Two different tool families
High speed steel is a tool steel. It carries tungsten, molybdenum, vanadium and chromium in a tempered martensite matrix. The name comes from the fact that it can harden in still air. A 10 mm HSS end mill sits around HRC 62–66, and it stays usable up to roughly 600 °C. Past that point the temper softens and the edge folds over.
Tungsten carbide is not steel. It is a powder metallurgy product: tungsten carbide grains sintered in a cobalt or nickel binder. Hardness lands near HRA 89–93, which is above HRC 70. It keeps that hardness to about 1,000 °C. That single number explains most of the cost gap and most of the speed gap between the two materials.
So when a machinist says tungsten steel, the part in the spindle is almost always a carbide insert or a solid carbide cutter. The material behaves like a ceramic in compression and like glass in tension. Push it wrong and it fractures instead of wearing.
- 1HSS is forged and heat treatedGrain structure comes from rolling and tempering.
- 2Carbide is sinteredGrain size and cobalt content set the grade.
- 3Both are called steel on the floorOnly HSS really is steel.
Hot hardness decides the cutting speed
Cutting generates heat at the shear zone. A large share of that heat goes into the chip, but the edge still sees several hundred degrees. HSS loses hardness above 600 °C, so the edge deforms and the tool rubs instead of cutting. That is why HSS speeds cap out around 25–40 m/min in plain carbon and alloy steel.
Carbide holds its hardness to about 1,000 °C, so the same cut can run at 120–250 m/min. Four to six times the speed is normal. On a 4,000 mm machine bed with long passes, that difference decides whether the job takes one shift or three.
The trade-off is toughness. Carbide has low transverse rupture strength compared with HSS. An interrupted cut, a hard spot in a casting, or a loose setup will chip the edge. HSS bends and recovers.
- 1Speed follows hot hardnessHigher temperature limit means higher surface speed.
- 2Toughness runs the other wayHSS absorbs shock that chips carbide.
When the cheap tool is the expensive one
A HSS cutter costs a fraction of a carbide one. That is true and also misleading. Tool cost per part is cutter price divided by the number of good parts it makes. On a 30-second cycle, a carbide tool at four times the speed can win even if it costs five times as much.
The math flips on low-volume and awkward work. A one-off fixture plate, a repair job, a prototype bracket: the setup time is fixed, the part count is one, and a cheap HSS cutter that survives a bad setup is worth more than a fast one that chips.
There is a middle ground worth knowing. Cobalt HSS grades and powder metallurgy HSS hold hardness higher than standard M2, and coated carbide handles harder stock than uncoated. Neither replaces the other, but both blur the line.
- 1High volume favors carbideSpeed cuts cycle time, which is the real cost.
- 2Low volume favors HSSForgiving edges survive marginal setups.
How each one dies, and what it tells you
HSS fails by wear and plastic deformation. The flank wears, the edge rounds, and the cut starts to burnish rather than shear. You hear it before you see it: a rising pitch and a spray of fine, hot chips that turn blue. Regrind and it comes back.
Carbide fails by chipping, thermal cracking and crater wear. A chipped corner shows up as a sudden change in chip color or a bright mark on the finished face. Thermal cracks come from running dry and then flooding with coolant, so keep the cooling method consistent through the cut.
Reading the failure correctly saves more money than any tool catalogue. If the edge is rounded and shiny, you ran too fast for the material. If it is broken off in a corner, the setup moved or the feed was too high.
- 1Rounded edgeHeat and speed, not load.
- 2Chipped cornerShock, chatter or hard inclusions.
- 3Fine comb cracksThermal cycling from stop-start coolant.
What this means for your parts at GreatLight
We run 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. Carbide tooling carries most of that work because cycle time drives cost on production runs. Maximum processing size is 4,000 mm, so long parts get long passes, and long passes are where carbide speed matters most.
HSS still has a place here. Taps, reamers, form tools and small-diameter drills in sticky stainless grades often run better in HSS or cobalt HSS. We hold ±0.005 mm and Ra 0.8–1.6 μm on turned and milled features, and the tool choice has to support that, not fight it.
If you are not sure which way a part should go, send the drawing. We quote and return a free DFM analysis within 12 hours, with the tooling approach and inspection plan attached. No minimum order quantity, from one prototype to 10,000+ part runs.
- 1Carbide for cycle timeMost milling and turning on production parts.
- 2HSS for threads and reamingWhere toughness and regrind cost matter more.
- 3Inspection on requestRaw material check, in-process monitoring, final inspection.
The verdict
For high-volume milling and turning in steel, pick tungsten carbide: the hot hardness pays for itself in cycle time. For tapping, reaming, form work and one-off setups, pick HSS: the toughness keeps a marginal job alive. Match the tool to the operation, not to the price tag.
Common questions
Is tungsten steel actually steel?
No. It is cemented carbide: tungsten carbide grains held in a cobalt or nickel binder by sintering. There is no steel matrix.
The name stuck because it is used in the same places as tool steel and looks similar when ground.
Can I run HSS at carbide speeds if I use coolant?
No. Coolant removes heat from the part and the chip, but the edge still reaches the shear-zone temperature. Above roughly 600 °C the HSS temper softens.
If you need carbide speed, you need a carbide edge. Flooding an HSS cutter harder just adds thermal shock.
Which is better for stainless steel, 304 or 316?
For milling and turning, coated carbide. Stainless work-hardens under the cut, so you want speed and a sharp edge that does not dwell.
For tapping, HSS or cobalt HSS with the correct pitch diameter. Carbide taps chip too easily when the torque reverses.
How many regrinds can I get from each?
An HSS end mill can take many regrinds because the whole body is the same hardened material.
A solid carbide cutter takes fewer, and the grinding wheel has to be diamond. Coated tools lose the coating on the first regrind, so recoating is a separate decision.
Why do my carbide inserts chip on castings?
Cast skin and sand inclusions are hard and abrasive. They shock the edge on entry.
Take a lighter first pass below the skin, or use a tougher grade with a honed edge. An interrupted cut on scale is the classic carbide killer.
Does tool material change the tolerance I can hold?
Only through rigidity. A sharp tool cuts; a dull tool pushes. If the edge rounds and starts burnishing, size drifts and surface finish goes cloudy.
We hold ±0.005 mm and Ra 0.8–1.6 μm on production parts, and tool condition is checked between runs to keep those numbers.
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