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Is carbide magnetic? How to tell carbide from steel
By CarbideBuyerUSA · Updated
Most tungsten carbide is magnetic, but only weakly, because the pull comes from the cobalt binder that holds the hard carbide grains together. A magnet on its own can still mislead you: carbide brazed to steel grabs like steel, and some grades use nickel or iron binders in place of cobalt, so check the weight and the look as well.
Is tungsten carbide magnetic? It depends on the binder
Carbide is not one metal. It is a sintered mix of tungsten carbide grains and a metal binder. A Lawrence Livermore paper on OSTI names cobalt, nickel and iron as binder metals, and ITIA, the tungsten industry association, says plain tungsten carbide and cobalt grades still predominate.
Cobalt is what a magnet finds. USGS describes cobalt as ferromagnetic, and the Cobalt Institute says “It has strong magnetic and catalytic properties”. A typical tool grade is mostly tungsten carbide, though: a US government profile puts commercial grades at roughly 3% to 16% cobalt.
That is why the pull feels soft. Oak Ridge researchers measured a carbide part with about 19% cobalt at a magnetic saturation of 0.5 tesla. The National Bureau of Standards (now NIST) measured pure iron in 1941 at 21.58 kilogauss, which works out to about 2.16 tesla. So even that cobalt-rich carbide carried less than a quarter of iron's saturation, and most tool grades hold less cobalt than that part did.
Nickel-bound grades
ITIA says wear parts are generally made of cobalt-bound carbide, and that cobalt-nickel-chromium, nickel-chromium, iron-nickel-cobalt and pure nickel binders are also taken into consideration when corrosion is a factor. Seal rings, dies and nozzles are the kind of parts that see that service.
A different binder can change how a piece answers a magnet, so we would not rule a wear part in or out on the magnet alone. Weigh it.
Sources: ITIA: Cemented carbides, a success story; OSTI: WC with iron and nickel binders; USGS Circular 1196-M (2004); Cobalt Institute: About cobalt; NTP: Hard metals background document (2009); OSTI: Binder jet printed WC-Co (ORNL); NBS: Saturation induction of iron (1941).
How to run the magnet test, and where it fails
USGS lists the response to a magnet among the checks scrap sorters use once a first look is not enough. It works best as a comparison, not a yes or no.
- Use a weak magnet, such as a refrigerator magnet or a small ceramic one. The difference you are feeling for is easier to notice with a weak magnet than with a strong rare-earth one.
- Hold it against a piece you know is steel, like a wrench or a drill chuck key, and feel how it snaps on.
- Now try the piece in question. A pull clearly softer than on the steel points to carbide; a snap just like the steel points to steel.
- Test the cutting end and the shank separately on any tool that might be tipped.
The test lets you down in three places:
- Steel attached to carbide. ITIA points out that much carbide is brazed onto, attached to or cast into steel parts. The steel in saw blades, tipped drills, road bits and tool holders grabs a magnet whatever the tip is made of.
- A weak or missing pull. On its own it does not prove a piece is carbide, and with an odd binder it does not prove a piece is not. Weigh it before it goes in the carbide bag.
- Mixed buckets. Do not sweep a mixed can with a magnet to pull out the steel, because cobalt carbide comes up with it. Sort those by eye and by weight.
Sources: USGS Circular 1196-M (2004); ITIA: Recycling of tungsten, part 1.
Weight: the test that rarely lies
Carbide is heavy for its size, and you can feel it. NTP lists tungsten carbide itself at a density of 15.6 g/cm³, and real grades come in a little lower because cobalt is lighter: a 2023 Washington State University study measured two commercial grades at 15.17 and 14.91 g/cm³, and a part with about 19% cobalt sat near 13.1. NIST lists iron, the base of every steel, at 7.874 g/cm³.
In round numbers, carbide is roughly twice as heavy as iron for its size, and steel is mostly iron. Hold a carbide end mill in one hand and a steel one of the same diameter in the other, and you will feel it.
A kitchen-scale check
For a number instead of a feeling, weigh a handful of the same kind of pieces dry, in grams. Set a cup of water on the scale and zero it, then hang the pieces on a thread so they sit fully under water without touching the cup. The new reading in grams is about their volume in cubic centimeters, since a cubic centimeter of water weighs about a gram.
Divide the dry weight by that reading. Carbide lands roughly between 13 and 15.6, against 7.874 for iron. A result well above that range points to tungsten metal: ITIA puts tungsten at 19.25 g/cm³, and we buy that too as tungsten scrap.
Sources: NTP: Cobalt-tungsten carbide profile; OSTI: WC-Co grade densities (2023); OSTI: Binder jet printed WC-Co (ORNL); NIST: element densities, table 1; ITIA: Properties and intermediates.
What carbide looks like up close
USGS says skilled sorters “do a preliminary sort on the basis of shape, object recognition, color, and weight” before they reach for any test. With carbide, the shape and the weight usually tell you more than the color.
- Coatings. ITIA reported in 2010 that more than 80% of turning inserts and about 70% of milling inserts are coated, and it lists TiN, TiCN, TiAlN and alumina among the layers. TiN is gold colored. The layers are thin, 2 to 20 microns by ITIA's figures, so a coated insert is the same carbide underneath.
- Bent or chipped. NTP describes tungsten carbide as hard and able to resist bending, but brittle. A tool that has bent is worth a second look before it goes in the carbide bag.
Look-alikes exist. USGS names ceramics and cermets among the substitutes for cemented carbide, and both are made into inserts that can pass for carbide at a glance; weigh them before you bag them together.
Sources: USGS Circular 1196-M (2004); ITIA: Cemented carbides, a success story; USGS Mineral Commodity Summaries 2026: Tungsten; NTP: Cobalt-tungsten carbide profile.
Carbide or high-speed steel
High-speed steel (HSS) is the material most often mistaken for carbide, because it is made into the same tools. In a 2008 newsletter, ITIA put about 95% of HSS into machining tools such as drills, taps, milling cutters, gear cutters and saw blades.
HSS does contain tungsten, anywhere from 1.5% to 20% according to ITIA, but it is still steel. Expect it to answer a magnet like your steel reference piece, and run the weight check on anything you are unsure of.
- Markings. ITIA names M2, M7 and M42 as the most popular high-speed steel grades in Western countries and Japan, so an M-number etched on the shank points to HSS.
- Cobalt drills. USGS counts the high-speed steels used for cutting tools among the cobalt-bearing steels. A drill sold as a cobalt drill is most likely one of those steels, not carbide.
- Saw blades. ITIA notes that bimetal blades carry M42 HSS teeth. On a carbide-tipped blade, the tips are separate pieces brazed onto the steel plate.
Keep HSS out of the carbide bag, not out of the truck. We buy high-speed steel scrap as its own material, and our page on carbide end mills and drills shows how to sort a tool crib into solid carbide, tipped tools and HSS.
Sources: ITIA: Tungsten in steel; USGS Circular 1196-M (2004); ITIA: Recycling of tungsten, part 1.
Leave the spark test to someone else
USGS also mentions reading the spark pattern from a grinding wheel. We would rather you did not. Cobalt-tungsten carbide powders and hard metals sit on the National Toxicology Program's list as reasonably anticipated to be a human carcinogen, and grinding is what makes the dust.
Whole parts are a different matter. ITIA says the normal and intended use of tungsten carbide articles is expected to produce little or no exposure to the user. Keep it that way: do not grind, cut or crush pieces to identify them.
Sources: USGS Circular 1196-M (2004); NTP: Cobalt-tungsten carbide profile; ITIA: Health and environment.
When to stop testing and send photos
If a weak magnet, the heft and the color all agree, you can bag the piece with confidence. If they disagree, or you have a bucket of odd wear parts nobody can name, stop there and let us look.
Spread the doubtful pieces out on a plain surface and take a few clear photos, with something for scale next to them. Close-ups of any markings and of the joint between a tip and its body help most. Send them through the quote form with what you think the pieces are and about how much the lot weighs, email help@carbidebuyerusa.com, or call (877) 838-9920.
Not sure is fine. We buy carbide in any form and the exotic metals that tend to get mixed in with it, so a lot does not have to be perfectly sorted before you ask. Ship it from anywhere in the US and we pay the shipping, or we pick up in every city in California, Arizona and Nevada, and we pay cash where state law allows.
Questions sellers ask
Does a magnet stick to carbide inserts?
Usually a little. Most inserts use a cobalt binder, so a weak magnet gives a light pull, much softer than on steel. A coating is only a few microns thick, so test coated and uncoated inserts the same way.
How do I tell tungsten from carbide?
Weigh it. Tungsten metal is denser than carbide, so the kitchen-scale check above gives a higher number for a tungsten piece. We buy both, so if you are unsure, send a photo with the question.
My carbide drill sticks hard to a magnet. Is it really carbide?
Check the shank. A strong snap usually means the tool is steel, or that a carbide tip sits on a steel body. Weigh it against a known steel drill of the same size, and if it is not clearly heavier, sort it with the high-speed steel.
Is carbide with a nickel binder still worth sending?
Yes. It is still tungsten carbide, and we buy carbide in any form. We quote each lot from its photos, form and weight, so tell us what you know about where the parts came from.
Can I use a magnet to clean steel out of carbide grindings?
Not reliably, because a magnet lifts cobalt carbide fines along with the steel. Keep the sludge as it is, dry if you can, and describe it on the quote form.
Keep reading
End mills and drills
Solid carbide end mills, drills, reamers and burs
Learn more
High-speed steel scrap
HSS and cobalt drills, taps and tool steel
Learn more
What is tungsten carbide?
What it is made of, grades and cobalt content
Learn more
How to sort carbide scrap
Keep it clean and separated to get the most for it
Learn more
Carbide inserts
Used indexable inserts, coated or uncoated, any shape
Learn more
Brazed carbide and saw tips
Carbide-tipped saw blades, saw tips and brazed tools
Learn moreGet a quote for your carbide
Tell us what form it is in, about how much it weighs, and send a few photos. Ship it to us from anywhere in the US and we pay the shipping, or we pick up in California, Arizona and Nevada.