WHY IS CARBIDEMAGNETIC?

Tungsten carbide itself is only weakly magnetic. But the cobalt binder — typically 3 to 25 percent of the tool — is strongly ferromagnetic, just like iron and nickel. The magnet is attracted to the cobalt distributed through the tool, so the whole insert or end mill responds to a magnet. It is not steel, it is not a fake, and nothing is wrong with it. That is simply how cemented carbide behaves.

The magnetism varies with the recipe. Higher-cobalt grades — the tougher ones — pull a magnet more strongly. Lower-cobalt grades pull more weakly. Some specialty grades use nickel binder instead of cobalt, and those respond differently. But for the standard tooling in your shop, expect the magnet to stick.

Tungsten carbide is extraordinarily dense: roughly 14 to 15 grams per cubic centimeter, nearly twice the density of steel at 7.85. Pick up a carbide end mill and a steel end mill of the same size, and the carbide one feels shockingly heavy — that heft is unmistakable once you have felt it, and it is the most reliable field test there is.

The practical identification sequence for a mystery tool:

• Weight first: unnaturally heavy for its size points to carbide
• Markings second: grade codes and brand marks laser-etched on the shank or box
• Spark test third: on a grinder, carbide throws short, dark-red sparks with little branching; steel throws long, bright, branching sparks (grind wet, with dust controls and a respirator)
• Magnet last: useful only to rule things out — aluminum and most stainless will not stick, while both carbide and steel will

For sellers, the practical upshot: do not let a magnet talk you out of money. Plenty of shops have tossed magnetic carbide assuming it was steel. If it is heavy, marked like tooling, and came from cutting service, it deserves a carbide quote before it goes anywhere.

Where the myth came from

The "carbide is non-magnetic" claim likely started as a garbled version of a real fact: tungsten carbide powder and pure tungsten are only weakly magnetic, and some non-cobalt specialty grades behave differently. Somewhere along the way, "some forms" became "all carbide," and the myth stuck because it sounds scientific. The cemented carbide in actual cutting tools — with its cobalt binder — has always been magnetic.

What recyclers actually test

Professional carbide buyers do not grade with a magnet. They identify the tooling type, weigh it, and test for carbide content — by XRF analyzer, chemical assay, or density checks depending on the lot. The magnet never enters the valuation. Any buyer who prices carbide off a magnet test is not grading it professionally.

Magnetism in the shop: the coolant connection

Carbide's magnetism has one practical shop consequence worth knowing: magnetic chip conveyors and magnetic separators in coolant systems pull carbide fines out of the coolant along with the steel chips. That is good news twice over — cleaner coolant and a concentrated carbide stream collecting exactly where the separator dumps. If your shop runs magnetic separation, the separator's catch is a tungsten stream: keep it apart from the steel chips and it has real value as carbide-bearing material.

Does magnetism affect the cut?

No. The magnetic response is far too weak to influence cutting forces, chip formation, or tool performance. It matters for identification, for separation equipment, and for winning arguments — not for speeds and feeds.