Cobalt vs Carbide End Mill: Which One Should You Buy?

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Cobalt vs carbide end mill: the short answer

Choose carbide for hard materials and long runs: the listings state micro grain carbide with higher hardness and wear resistance than high-speed steel, plus stronger heat resistance than HSS. Cobalt enters the picture as the binder inside the carbide itself. The LU&MN listing says it modifies the proportions of tungsten carbide and cobalt to reach the desired hardness, and the Hunricho listing says its tungsten steel is mainly tungsten carbide and cobalt, accounting for 99% of all components. So the real shopping decision is which carbide grade, coating and flute count fits the job.

What the listings state about hardness

Hardness ratings are the most useful numbers here. The Home of quality tools 3/4 inch mill is rated HRC45 and lists carbon steels around HB225, alloy steels from HB225 to 325, pre-hardened steels up to HRC45, hardened steels from HRC40 to 45, and cast iron. The LU&MN set suits materials under HRC50. The WEXWE mill states HRC68 ultrafine grain tungsten carbide, the hardest stated here, aimed at high hardness steel finishing. Match the rating to the stock: a mill rated HRC45 is not the pick for stock harder than that rating.

The gear: four carbide end mills, ranked

Ranked by the listings’ stated specs, the WEXWE 6-flute mill leads: HRC68 carbide, a 50 degree helix angle, Balzers PVD coating, five-axis grinding and a stated check of each bit on a detecting instrument with a laser-marked code. Next is the LU&MN 5-piece 1/4 inch set: solid carbide with TiAlN coating, a 3/4 inch cutting length, 1/4 inch shank and 2-1/2 inch total length, rated for materials under HRC50 and compatible with desktop CNC machines. Third is the Home of quality tools 3/4 inch single: AlTiN coating, 4 flutes and the widest stated material list, though its spec table lists the material type as high speed steel and tungsten carbide while the title and bullets say carbide. Fourth is the Hunricho 8-piece metric set covering 2 to 12 mm in 2, 3, 4, 5, 6, 8, 10 and 12 mm sizes; note its spec table lists the material as high speed steel while the bullets say tungsten steel carbide.

Coatings and flute counts

Three of the four state a coating. The Home of quality tools mill uses AlTiN, which the listing says gives hot hardness and oxidation resistance. The LU&MN set uses TiAlN on solid carbide. The WEXWE uses a Balzers PVD coating. The Hunricho set is unfinished, with no coating stated. On flutes: three listings state 4 flutes for general milling and finishing, while the WEXWE states 6 flutes, which the listing says reduce the cutting load on each edge for smoother finishing. More flutes suit finishing passes, per the WEXWE listing.

Match the mill to the machine and the job

Shank size has to fit the collet. The LU&MN set uses a 1/4 inch shank and states compatibility with desktop CNC machines. The WEXWE uses a 1/2 inch shank with a 1.25 inch cutting edge and 3 inch overall length. The Home of quality tools mill is a 3/4 inch single, 3.93 inches long and 0.75 inches wide. For small desktop work, the 1/4 inch LU&MN set or the metric Hunricho set in 2 to 12 mm sizes fit better than the 3/4 inch single. For finish work on hard steel, the WEXWE’s 6 flutes and HRC68 rating are the stated answer. See our ball nose vs flat end mill guide for the other half of the cutter-shape question, and browse CNC tooling for more.

Two listing contradictions to note

Two listings contradict themselves on material. The Home of quality tools mill is sold as carbide in the title and bullets, but its spec table lists the material type as high speed steel and tungsten carbide. The Hunricho set’s bullets say tungsten steel carbide while its spec table lists the material as high speed steel. In both cases the title and bullets are more specific, so treat the mills as carbide, but the mixed spec tables are a reason to confirm with the seller before buying for hard steel.

FAQ: lasers and CNC

Is carbide always better than cobalt HSS?

For hardness and wear resistance, the listings favor carbide: higher hardness than high-speed steel and stronger heat resistance than HSS. None of the four listings is a cobalt HSS mill, so compare on the stated HRC ratings.

What does the cobalt do in a carbide end mill?

It is the binder. The LU&MN listing says it adjusts the proportions of tungsten carbide and cobalt to reach the target hardness, and the Hunricho listing says tungsten carbide and cobalt make up 99% of its tungsten steel.

Which coating should I pick?

The listings state AlTiN for hot hardness and oxidation resistance, TiAlN on the LU&MN set, and Balzers PVD on the WEXWE. The Hunricho set is unfinished. Pick the coated option when the listing ties the coating to the material being cut.

How many flutes do I need?

Three listings state 4 flutes for general and finish work; the WEXWE states 6 flutes for smoother finishing with less load per edge. The listings do not state a 2-flute option, so for heavy roughing in soft material, look beyond these four.

Can these mills run on a desktop CNC?

The LU&MN listing states compatibility with desktop CNC machines and other industrial CNC machines, with a 1/4 inch shank to match the collet. The other three listings do not state desktop compatibility, so check the collet and spindle first.

Related: the ball nose vs flat end mill guide, CNC tooling and desktop CNC routers.