A loop that cut cleanly at the start of a session is pushing rather than cutting by the end of it. The edge has worn away while you worked. That is the problem tungsten carbide exists to solve.
Tungsten carbide is on the end of a lot of trimming tools, and it is not a metal.
It is a composite. Hard grains of tungsten carbide, a compound of tungsten and carbon, held together by a softer metal called a binder, almost always cobalt. The trade name for the finished material is cemented carbide, or hard metal. Nothing about it is cast or forged.
How it is made
Tungsten ore concentrate is converted to tungsten oxide, then reduced to tungsten metal powder. That powder is carburised with carbon at high temperature under hydrogen, and this is the step where tungsten carbide itself forms.
The carbide powder is then milled together with the binder until every carbide particle is coated, granulated so it flows, pressed into shape, and sintered, which means heated until the binder melts and wets the carbide grains, drawing them together into a solid. Cobalt is the usual binder for exactly that reason: it wets tungsten carbide better than the alternatives do.
The part comes out of the furnace smaller than it went in, and then it is ground to its final shape and its cutting edge. A trimming tip has been through a furnace more than once before it ever meets clay.
That route is set out in Reactive Sintering of Cemented Carbides, published open access in 2025 by a group at the University of Mons, which is also the source for the figures further down.
Grades differ, mostly by how much binder is in there and how fine the grains are, and the two pull in opposite directions. More binder gives a tougher, softer tool. Finer grains give a harder one that holds a keener edge. Almost nobody in the pottery trade publishes a grade, ourselves included, because the makers do not state it.
Why it keeps cutting
Hardness here is measured by pressing a diamond point into a surface under a set load and measuring the dent it leaves. On the Vickers scale, written HV, the Mons paper takes 1700 to 1900 HV as the target for a cutting grade, alongside a fracture toughness of at least 10 MPa·m½. Hardened tool steel sits a long way below that, which is the whole point of putting carbide on the end of a tool.
That gap matters more in trimming than in most cutting, because trimming is abrasion rather than slicing. You are dragging an edge through a clay body full of grog and quartz, both of which are hard. A steel edge is being worn away the whole time it works. Carbide is harder than most of what is in the clay, so the edge stays where it is.
The handling is different too. A carbide tip wants light pressure. If you are leaning on it the way you lean on a tired steel loop, you are working against it.
Why it chips
Hardness and toughness are a trade, and you do not get both. The published work on carbide compositions is consistent on this: as toughness goes up, hardness comes down, and the other way round.
The binder is the only thing in the tip providing any toughness. The carbide grains provide the hardness. So the grades that cut longest are also the ones that chip soonest.
Which comes down to one thing in the studio. A steel tool bends before it breaks, and dulls as it works. A carbide tool does neither. It chips. Dropped onto a concrete floor, a tip can break.
Carbide is dense, too. Pick a tip up and it feels heavier than its size suggests.
Replaceable is not the same as repairable
A broken carbide tip cannot be repaired. There is no sharpening your way out of a fracture and no sticking it back together. What that costs you depends entirely on how the tool is built, and carbide tools come in two families.
On a fixed tool, the carbide is set into the handle with a brass collar and glued. The tip is part of the tool. If it breaks, the tool is finished.
On a modular tool, the tip is a separate part held in a collet or a socket, designed to come out. A broken tip is still broken, but you replace the tip rather than the tool, and the handle you have got used to stays in your hand.
Out of the handle a blade is very little: the carbide loop, and the solid shaft the collet grips. Profiles differ by maker and by tool, and that is the part you choose. The shaft is what has to match the handle you already own.
That difference is most of the argument for spending more at the start. It is not the whole argument, because the fixed tools are better to hold.
The wooden handled ones
Most of the carbide tools we sell are not modular, and they are the ones most people buy. Our Carbide Trimming Tools start at £37.50 and come in several profiles on turned rosewood handles with brass ferrules. The Tungsten Carbide Hook Trimming Tool is £50, a carbide loop in a brass collar on a mahogany handle.
They are worth having for reasons the modular tools cannot match. Wood is warmer and quieter in the hand than knurled aluminium, it does not get slippery in the same way, and a turned handle sits differently in a long trimming session. They are lighter, and they cost less: £37.50 to £54 against £69 to £86 for the modular tools.
What you give up is the repair. The tip is glued in, so a chip ends that tool rather than costing you a replacement head. In practice that means treating them with more care than you would a steel loop: not dropping them, not levering with them, not leaving them loose in a tin where they knock against each other.
If you trim a lot and you are hard on tools, the modular systems earn their price. If you trim carefully, the wooden handled ones will last for years and you will enjoy using them more.
Where tungsten comes from
Two ores: scheelite and wolframite. China mined 67,000 of the 85,000 tonnes produced worldwide in 2025, close to four fifths of world supply, and holds about 2.5 million tonnes of the more than 4.7 million tonnes of world reserves. The numbers are from the US Geological Survey's Mineral Commodity Summaries, published February 2026, which is the standard annual reference for this.
Most tungsten does not become pottery tools. The same survey puts about 60% of United States tungsten consumption into cemented carbide parts for cutting and wear, mainly for construction, metalworking, mining and oil and gas drilling. Trimming tools are a small corner of a large industry, which is why their price moves with things that have nothing to do with ceramics.
Two of those things landed in quick succession. At the end of 2024 the United States raised tariffs to 50% on several tungsten products from China, and in February 2025 China brought in export licensing on selected tungsten items. Prices rose sharply through 2025 as a result: the USGS records ammonium paratungstate going from $331 to $675 per metric tonne unit on the Rotterdam market across the year, and concentrate from $266 to $551. When carbide tools go up in price, that is usually why.
Tungsten steel is a different material
You will see both names in a pottery shop, and they do not mean the same thing.
Tungsten steel is steel, alloyed with tungsten and usually small additions of molybdenum and vanadium. High-speed steel is the familiar example. It behaves like steel: it bends before it breaks, it dulls as it works, and you sharpen it. Plenty of good trimming tools are made of it, including our Tungsten Steel Pottery Trimming Tools at £45, and no carbide is involved anywhere in them.
Tungsten carbide is the sintered composite described above, and it is not a steel at all. The two names get used loosely across the trade, partly because suppliers' own catalogues translate them interchangeably.
In practice you can usually tell by looking. A carbide-tipped tool has a small, separate, pale grey tip set into a steel shank or a handle, and you can see the joint where one material meets the other. A tungsten steel tool is one piece: the cutting end and the shank are the same metal and the same colour all the way through.
Looking after one
Do not drop it. The rest is housekeeping.
Dry it rather than leaving it in the water bucket. Tungsten carbide does not rust, but the shank and the handle will, and water sitting in a collet or a handle joint is where a tool quietly dies. Rinse, wipe, put it away.
Trim between leather-hard and bone-dry. Carbide is not for wet clay, and light pressure is the whole technique.
Store the tips so they are not knocking into each other. A roll, a case, a soft surface, anything that keeps carbide away from carbide and away from the floor.
Sharpening, if it comes to it. After months of regular work an edge can dull slightly. The tool for that is a fine diamond file, 400 grit or finer, worked on the inside face only, because the outside face is bevelled and does not want touching. An ordinary whetstone will make little impression. Whatever you use, keep the work wet and light: cobalt dust is not something to be making in a studio, which is reason enough to leave the bench grinder out of it.
The modular systems we stock
Two of them, both tungsten carbide tipped, and they suit different scales of work.
Tortuga Tools have aluminium handles with silicone grip covers, in colourways, and replaceable tips. This is the range we keep deepest, and the one to start with. The two double-ended tools are the strongest things in it: The Delta & Loop at £76, with a flat Delta end for straight lines and defined shapes and a curved Loop end for rounded contours, and The Mini Delta & Loop at £76, the same two tips sized down for small pots and fine detail. The Dome at £76 has a large curved edge and a flat side, giving several cutting angles on rounded and bellied forms. The Seven at £76 is ground for tight corners, sharp angles and clean foot rings. The Hook at £86 works curved forms from either side, inside or out, and its flat side doubles as a thumb rest. The larger handle makes Tortuga the better fit for bigger work.
BuschKraft is a modular system designed by Nicholai Busch and made in the USA. The handle is machined anodised aluminium, knurled and tapered, and the system takes its proportions from drafting pens. A stainless steel collet holds any solid tip with a 3 to 4.5mm shaft, swapped by hand with no extra tools. The Delta blade at £69 is a triangle with three radii, its two upper corners reaching into smaller details and transitions. The Classic 7 at £69.95 is a flat cutting edge with a small square tip, hooked so it reaches inside a foot. Both come fitted on a handle, though the Classic 7 is sold out at the moment, and the Dragonfly carving starter kit is £88. For carving rather than trimming there are also blade packs, the 5-Piece Arc pack at £35 and the 5-Piece Detail 2 pack at £25, which drop straight into the same handle. BuschKraft's loops run smaller and more delicate than Tortuga's, so it suits work at a smaller scale.
Because both are modular, one handle will carry several heads. The reason to own two handles is not the tools, it is wet hands: swapping a tip mid-pot with slip on your fingers is worth avoiding.
Whether you need one
If you trim a few pots a month, a steel loop and a whetstone will serve you well, and that is a reasonable thing to buy instead.
If you trim every week, on grogged stoneware, and you have spent part of a session fighting a dull edge, carbide is not a luxury. It is the tool that stops you pushing.
You can hold most of them in the shop in Peckham before you decide.
Sources
- Stanciu, V.I., Mégret, A., Mouftiez, A., Vitry, V. and Delaunois, F. Reactive Sintering of Cemented Carbides. Alloys, 2025, volume 4, article 15. Open access.
- US Geological Survey. Tungsten, in Mineral Commodity Summaries, February 2026.
Where to go next
- Where to buy ceramic supplies in London, for the rest of the shelf.
- How to glaze pottery, for what happens after the trimming.
