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We buy carbide sludge, grindings and powder
Carbide sludge is the dark grey paste that builds up under a carbide tool grinder, and we buy it, along with dry swarf, loose powder and dust collector fines. Send a photo and a rough weight through the quote form or call (877) 838-9920.
Soft scrap: what sludge, swarf and powder are
Recyclers split carbide scrap into two families. Hard scrap is solid: inserts, end mills, rods, dies. Soft scrap is everything fine, and a USGS report on tungsten recycling (data from 2000) lists it as baghouse dust plus "cutting or grinding sludges, loose powders generated during powder metallurgical processing, swarf, and turnings".
In a shop it collects wherever carbide meets a wheel: tool and cutter grinders, regrind benches, surface grinders that finish dies and wear parts. The International Tungsten Industry Association (ITIA) shows a small carbide end mill, made for dental work, getting its final shape by grinding with diamond tools after sintering. ITIA also notes that carbide rod may be ground into a drill or an end mill, so cutting flutes puts carbide into the coolant.
ITIA says most soft scrap is recycled by chemical conversion into ammonium paratungstate (APT), the main high-purity intermediate for most tungsten products. That route uses more energy and chemicals than the direct recycling used for sorted, clean solids.
Sources: USGS Open-File Report 2005-1028, tungsten recycling in the US (data year 2000); ITIA, Cemented carbides: a success story (newsletter, June 2010); ITIA, Recycling of tungsten part 2 (newsletter, August 2019); ITIA, Recycling of tungsten part 1 (newsletter, May 2018).
How to tell it is carbide grinding sludge
Color tells you little, because carbide fines, steel swarf and wheel grit look alike once they settle in coolant. The reliable clue is the machine: a grinder that only sees carbide on a diamond wheel makes carbide sludge, and one that does steel in the morning and carbide after lunch makes a mix.
Weight is a second hint. US government tables put tungsten carbide at 15.6 g/cm³ and iron at 7.874 g/cm³, about half that, so drained carbide fines feel heavy for their size. ITIA puts the tungsten in high-speed steel at 1.5 to 20%, while NTP says most commercial carbide grades are 50% to 97% tungsten carbide and other carbides. HSS swarf from a shared machine thins a lot out.
Sources: NTP Report on Carcinogens profile, cobalt-tungsten carbide; NIST X-ray mass attenuation tables, element densities; ITIA, Tungsten in steel (newsletter, December 2008); NTP Report on Carcinogens background document, cobalt-tungsten carbide (2009).
Handling carbide sludge and dust safely
The risk is dust in the air, not the tool in your hand: ITIA says normal use of finished carbide articles is expected to produce little or no exposure. OSHA reports that of 12 workers who made or ground tungsten carbide tools and developed interstitial lung disease, eight died; it adds that cobalt dust can scar the lungs and sensitize the airways and skin.
For tungsten carbide with more than 2% cobalt, the air limits are written as cobalt, averaged over a work shift:
- OSHA permissible exposure limit (the federal legal limit): 0.1 mg/m³
- NIOSH recommended limit: 0.05 mg/m³
- Cal/OSHA permissible exposure limit: 0.02 mg/m³, five times tighter than federal
OSHA's listed controls are process enclosure, local exhaust ventilation, general dilution ventilation and personal protective equipment. Dry fines are also a fire concern: OSHA warns, "Dusts of cobalt metal or cobalt compounds may form explosive mixtures in air."
Scoop sludge rather than sweeping or blowing it around, wear gloves, and never dry it with a torch or oven. Your shop's safety program comes first; this is not medical advice.
Sources: OSHA, cobalt dust health hazards; OSHA chemical data, tungsten carbide (cemented); ITIA, health and environment.
Sealed containers, oil and water
Store soft scrap in a container whose lid seals, such as a steel or heavy plastic pail with a gasket lid, or a lidded drum. Use one container per machine and write on the lid what was ground and which coolant that machine runs.
Let sludge settle, then pour or pump off the standing coolant before sealing it. Do not add water, and keep rags, filter paper, wheel stubs and floor sweepings out. Oil and water add weight that is not carbide. At the conversion plant, heat comes first: USGS describes soft scrap being heated in air to oxidize the tungsten so it dissolves under alkaline conditions.
Old coolant has its own hazard. OSHA says poorly managed metalworking fluids can cause skin irritation, dermatitis and eye, nose and throat irritation. Dry powder goes in a sealed heavy bag inside a lidded pail, so nothing puffs out when the lid comes off.
Sources: USGS Open-File Report 2005-1028, tungsten recycling in the US (data year 2000); OSHA, metalworking fluids: health effects.
Carrier rules before wet or oily sludge ships
No USPS or FedEx page we found names grinding sludge. Their liquid and hazardous materials rules apply, and they put the job of knowing the contents on the shipper. USPS Publication 52 (August 2026 edition) makes the mailer responsible for identifying flashpoint, toxicity, corrosiveness and any other hazardous property before deciding whether a package can go in the mail.
- USPS bans flammable liquids with a flashpoint of 20°F or below. It takes combustible liquids by domestic ground only as Limited Quantity consumer commodities, by domestic air only as ID8000 materials, and never in international mail.
- A USPS package holding liquid must be marked as liquid and carry orientation arrows.
- FedEx Ground ships hazardous materials only for shippers it has approved.
- USPS refuses any mailpiece over 70 pounds; FedEx Ground stops at 150 pounds, and heavier goes as freight.
So drain the liquid, seal the container, and call us before you pack it, with the name of the coolant or oil and its safety data sheet if you have one. What rules apply depends on what is in it, which is better settled on the phone than with a pail sent back.
Sources: USPS Publication 52, section 323 (August 2026 edition); USPS Publication 52, flammable and combustible liquids; USPS Domestic Mail Manual 601 (liquids); USPS Domestic Mail Manual 201 (weight limit); FedEx, how to ship hazardous materials; FedEx Ground limits; FedEx freight.
Selling carbide sludge and powder scrap
A photo of the open container, a rough weight or pail count and what was ground are enough to start, sent through the quote form or to help@carbidebuyerusa.com. Each lot gets its own quote, since no two shops' sludge carries the same mix of carbide, coolant and grit.
Sellers anywhere in the US can ship it to us, and we pay the shipping. We also come to you and pick up pails and drums of sludge in every city in California, Arizona and Nevada (see pickup). We pay cash where state law allows; the state rules guide explains the Arizona and Nevada payment limits.
Worn tools from the same grinding room sell as hard scrap: see end mills and drills, inserts and sorting carbide scrap.
Questions sellers ask
Do you buy tungsten carbide sludge that is still wet?
Yes. Let it settle, pour off the standing coolant and seal the rest in a lidded pail or drum. Tell us the coolant before it ships.
Is carbide powder scrap worth as much as solid carbide?
Pound for pound it usually holds less carbide, because it carries coolant, wheel grit and sometimes steel fines. The cleaner and better separated the lot, the more of each pound is carbide.
Do you pick up drums of carbide sludge?
Yes, in every city in California, Arizona and Nevada. Everywhere else you ship it to us and we pay the shipping; call first so we can talk through the container and carrier.
Keep reading
End mills and drills
Solid carbide end mills, drills, reamers and burs
Learn more
How to sort carbide scrap
Keep it clean and separated to get the most for it
Learn more
Ship your scrap
Ship from anywhere in the US; we pay the shipping
Learn moreCarbide recycling
Why used carbide is worth recycling and what happens to it
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.