Carbide recycling for machine shops, from the bin to the sale
Carbide recycling for machine shops starts with one habit: a closed container kept only for carbide, so worn tools stay clean and easy to price. This guide covers that bin, the coolant, dust and EPA rules, and each kind of buyer, our quote included.
Where carbide scrap comes from in a machine shop
It is worn or broken tooling, such as inserts with every edge spent, end mills, drills and round tools past regrinding, plus the sludge and swarf from grinding. Each is cemented carbide: hard carbides, mainly tungsten carbide (WC), held in a tough binder such as cobalt, nickel or iron.
An insert is a replaceable tip with several cutting points; university slides count 8 on a square insert. It is indexed (rotated in its holder) as each edge wears, and scrapped when all are spent. An end mill is a milling cutter; carbide ones and carbide drills are ground from rod. A brazed tool has a carbide tip bonded to a shank with brazing or soldering material.
USGS calls solid pieces such as these hard scrap, and fine material such as grinding sludge, swarf and turnings soft scrap.
Sources: King Saud University, cutting tool materials slides (2010 textbook); King Saud University, metal cutting lecture (2010 textbook); ITIA, Cemented carbides (newsletter June 2010); ITIA, recycling of tungsten products (newsletter May 2018); USGS Open-File Report 2005-1028, tungsten recycling.
How shops judge when a carbide tool is worn out
Tool life is usually judged by flank wear, the worn band the freshly cut surface rubs into the side of the edge, because crater wear on the tool face is harder to measure.
| Standard | Use | End of tool life |
|---|---|---|
| ISO 3685:1993, as a paper citing it describes | Sintered carbide tests | 0.3 mm average flank wear or 0.6 mm maximum, the thresholds it calls most commonly used |
| ISO 8688, as a 2022 milling study applied it | Milling, coated carbide | 0.3 mm average or 0.5 mm maximum, whichever came first |
A tool-wear course says tools should be reground when average flank wear reaches a set allowable value, and that once wear enters its rapid third stage, regrinding is uneconomical. A 2008 thesis adds that margin wear might limit how many regrinds a drill can take before it must be discarded.
Sources: AAST course IM212, Tool Wear - Tool Life (2017); Karandikar, Abbas and Schmitz, tool life (Precision Engineering 2013); Materials Science Forum vol. 986, citing ISO 3685:1993; Materials (2022), coated carbide milling of AISI 4340; University of North Texas thesis (2008).
Setting up a carbide bin: what goes in and what stays out
Give carbide its own closed container at each machine or in the tool crib, and keep high-speed steel (HSS), steel chips and other metals out. A 2021 recycling review, discussing zinc reclaim, says poor sorting directly lowers the quality of the reclaimed powder, and USGS says the zinc process, which uses hard scrap such as used inserts, is not a purification process, so careful sorting and removing oil, solder and coatings is essential.
HSS is easy to mix in: ITIA (2008) says about 95% of it goes into machining tools such as drills, taps, milling cutters and saw blades. A university lecture puts carbide at generally 1.5 to 2 times denser than steel, so a carbide drill outweighs a steel one of the same size.
Carbide left on a mostly steel tool can go out with the steel scrap and be melted into structural steel, and its tungsten and cobalt are lost. Bag brazed tools apart, since their solder must come off before processing. Kennametal's online terms, as archived in February 2025, ask for closed metal containers of no more than 1,000 lb, with carbide free from contaminants, ceramics, cermets and steel.
Sources: Zeiler et al., tungsten recycling review (2021, ITIA-hosted); USGS Open-File Report 01-349; ITIA, Tungsten in steel (newsletter December 2008); University of Pennsylvania IPD 501, speeds and feeds lecture; ITIA, recycling of tungsten products (newsletter May 2018); Kennametal US recycling terms (Internet Archive, February 2025).
Coolant, grinding dust and sludge: the rules that apply
Drain coolant off tools before binning them. OSHA says metalworking fluids can harm health through skin and breathing; its enforceable general-industry limit for mineral oil mist is 5 mg/m3 (Table Z-1). Its fluids manual reports a 1998 NIOSH recommended limit for fluid aerosols of 0.4 mg/m3 thoracic (about 0.5 total), but the manual is advisory, not law.
The tungsten industry association, ITIA, expects little or no exposure from normal use of finished carbide, while the National Toxicology Program says cobalt and carbide dust can come from sharpening or grinding. For carbide over 2% cobalt, OSHA's table lists limits of 0.1 mg of cobalt per cubic meter (OSHA), 0.05 (NIOSH, a recommendation) and 0.02 (Cal/OSHA). For cobalt dust, OSHA lists process enclosure, local exhaust and general ventilation, and protective equipment. IARC (2006) notes that reused grinding coolant builds up dissolved cobalt.
A 2023 study says grinding sludge, a mix of abrasives, lubricants and carbide chips, is currently recycled only chemically. Keep it sealed and leak-proof, and tell any buyer which coolant was used.
Sources: OSHA, Metalworking fluids; OSHA, Metalworking fluids: standards; OSHA, Metalworking Fluids Best Practices Manual; ITIA, Health and environment; NTP Report on Carcinogens, cobalt-tungsten carbide profile; IARC Monographs Volume 86 (2006); OSHA chemical data: tungsten carbide with more than 2% cobalt; OSHA eTool, cobalt dust; Pacini et al., grinding sludge (Materials 2023).
Machine shop scrap metal and the EPA rules
Under federal rules, scrap metal a shop sends for recycling is either excluded from the definition of solid waste or exempt under 40 CFR 261.6; wet sludge is the case to check. Under 40 CFR 261.1, prompt scrap is the turnings, cuttings and borings the metalworking industry makes, and processed scrap includes metal sorted by type; 261.4(a)(13) lists both, being recycled, among materials that are not solid wastes. Worn tools fit EPA's description of obsolete scrap, metal that has outlived its original use, and 261.6(a)(3)(ii) frees recycled scrap metal that is not excluded from parts 262 through 268, 270 and 124.
Two limits apply: EPA says smelting and refining sludges, liquid metal wastes and "metal-containing wastes with a significant liquid component" do not meet the definition of scrap metal, so wet grinding sludge is not automatically covered, and states can be stricter, so ask your state environmental agency before shipping sludge or swarf.
Sources: eCFR, 40 CFR 261.1; eCFR, 40 CFR 261.4; eCFR, 40 CFR 261.6; EPA, response to comments on the scrap metal exclusion (archived).
Tool makers' buyback programs for shop carbide
A buyback program is a tool maker's offer to buy used carbide back. The Kennametal, WIDIA and Sandvik Coromant terms below come from each company's own US pages, via dated Internet Archive captures; Seco's come from its own undated page. Other makers may run carbide buyback programs too; ask them or your distributor.
| Program | What it takes | Terms to know |
|---|---|---|
| Kennametal | US page, as archived in February 2026: inserts; drills, end mills and reamers; frac seats; road milling bits and soft scrap; US, Canada and Germany. | Online terms, as archived in February 2025: Kennametal customers only, not brokers or dealers; 3,000 lb a month online; seller prepays freight; Kennametal's weight is final; net 30. |
| WIDIA | US page, as archived in January 2026: its program runs in the US, Canada and Germany. | Ask WIDIA for its terms. |
| Sandvik Coromant, US page (archived January 2026) | Stand-alone inserts and solid carbide round tools, coated or not; nothing brazed, no cermet or ceramic. | Free containers, an RRA purchase order number and a per-pound quote, then the confirmed weight and a mailed check. |
| Sandvik Coromant, US terms (archived May 2026) | Inserts and round tools of any brand; solid tools under 160 mm and 8 kg; no ceramic, cermet, CBN, PCD or HSS. | Buyer Sandvik AB; orders on its online platform; invoice only after Sandvik collects; then 30 days to pay an undisputed invoice, or a credit against a future Sandvik invoice. |
| Seco (undated, no region named) | Any carbide product; no steel, ceramic or cermet. | Bins supplied; price depends on the market. |
Kennametal's terms, as archived in February 2025, also let it reject any shipment for any reason, unpaid. Sandvik Coromant's two pages differ; confirm which applies.
Sources: Kennametal US carbide recycling page (Internet Archive, February 2026); Kennametal US recycling terms (Internet Archive, February 2025); WIDIA US carbide recycling page (Internet Archive, January 2026); Sandvik Coromant US recycling page (Internet Archive, January 2026); Sandvik Coromant US recycling terms (Internet Archive, May 2026); Seco Tools, carbide recycling.
Scrap yards, specialist carbide buyers and our offer
A shop can also sell to a general scrap yard, a specialist carbide buyer or us. A 2021 review notes that scrap traders actively collect carbide cutting-tool scrap. Ask any yard how it grades, weighs and pays for carbide before you load up.
Our side: Carbide Buyers USA is family owned and operated and buys scrap carbide in any form and any brand, plus exotic metals and alloys. Ship from any US state and we pay the shipping, or have us pick up in any city in California, Arizona or Nevada. We pay cash where state law allows. Send photos, the form and a rough weight through the quote form or to help@carbidebuyersusa.com.
Sources: Zeiler et al., tungsten recycling review (2021, ITIA-hosted).
How to compare offers for a shop's carbide
Compare offers line by line on the same weight. Ask each buyer how it prices inserts, round tools, brazed tools and sludge; what deduction it takes, meaning weight or value subtracted for coolant, steel or other material; who pays freight; whose scale sets the weight; what happens to rejects; and how it pays.
Enter them in the carbide offer calculator. For a sole proprietor, scrap sales are business income on Schedule C, line 6, per IRS Publication 334 (2025), so keep records and ask your tax professional how that applies to your shop.
Then ask us for a quote and set it beside the other buyers in where to sell carbide.
Sources: IRS Publication 334 (2025).
Questions people ask
Should machine shop carbide scrap share a bin with steel chips?
No. In steel scrap it can be melted into steel, losing its tungsten and cobalt, and several program terms above exclude steel.
Can a shop sell carbide from several tool brands in one lot?
Often. Some programs' terms take any brand; others are meant only for the maker's own customers. We buy carbide of any brand, in any form.
Is wet grinding sludge treated like scrap metal under EPA rules?
Not automatically. EPA says metal-containing wastes with a significant liquid component, and smelting and refining sludges, fall outside its scrap metal definition, and states can be stricter.
Do you pick up carbide from machine shops?
Yes, in any city in California, Arizona and Nevada. From other states, ship it and we pay the shipping. Start with the quote form or call us.
Keep reading
Manufacturer buyback programs
What the tool makers' recycling programs take, who can use them and how they pay
Offer comparison calculator
Put two or three offers side by side and see what each pays after shipping and deductions
Scrap yard or carbide buyer?
What a general scrap yard does with carbide, and when a specialist makes sense
Estate and shop cleanouts
Clearing out a machinist's tools: finding the carbide and selling it
Have carbide to sell?
Tell us what form it is in and about how much it weighs, and add a few photos. Ship it from any state and we pay the shipping, or we pick up anywhere in California, Arizona and Nevada.