ER40 12mm High Precision Spring Collet Woodworking CNC Machine Tool

Need a 12 mm shank bit to run true in a woodworking CNC spindle? This is the part that holds it: ER40 12MM, an ER40-body spring collet with a 12 mm bore, made from alloy spring steel for woodworking CNC machine tooling. It is a wear part, sold as one collet under SKU ER40 12MM. Two things decide the fit — an ER40 nut and a 12 mm shank — and both are printed in the name. Price on request.

Three things go wrong on a woodworking CNC machine that runs 12 mm tooling: the collet loses its spring and the bit creeps mid-cut, a replacement arrives with the right bore but the wrong body and will not seat in the nut, and the machine stands idle while someone hunts a drawer of unmarked collets for one that measures 12 mm.

The ER40 12MM spring collet is built to end all three. It is an ER40 collet — the body size that has to match the ER40 nut on your spindle — with a 12 mm bore for a 12 mm nominal shank. Both figures are in the SKU, so nothing has to be guessed: ER40 is the body, 12 mm is the bore.

The body is alloy spring steel, and the material is the mechanism. A collet is a spring: the nut squeezes it closed around the shank and it has to open again when the nut is released, changeover after changeover. Spring steel is chosen so clamping is the same on the hundredth tool change as on the first. It is one piece — no separate jaws, no key, no insert.

It is a wear part for woodworking CNC machine tools: routers, boring heads and drilling units that take 12 mm shank tooling. Origin China, brand Shunhongyu, price on request — send the SKU and the quantity.

What the ER40 12MM collet gives you at the spindle:

• ER40 body size — it matches an ER40 nut and ER40 chuck, so the part number and the machine hardware agree on ER40.
• 12 mm bore — it takes a 12 mm nominal shank and nothing else; the bore is stated in the SKU, not left to a caliper.
• Alloy spring steel — the one-piece body compresses under the nut and springs back on release — the entire function of a collet.
• Grip around the circumference — the collet closes on the shank all the way round instead of at three jaw points, so a 12 mm bit is carried on its full surface.
• High precision, as specified — the item is listed as a highly precise collet; concentricity to the spindle axis is the property being bought, held at the bore and the seat.
• Single-piece simplicity — no jaws, no key, no adapter to lose: one collet, one nut, one tool change.
• Woodworking CNC application — listed for tools on woodworking CNC machines — routers, boring heads and drilling units running 12 mm shank tooling.
• Wear part, replaced alone — when it is spent, the collet goes in the bin and the nut, chuck and spindle stay at their datum.
• Origin and brand — made in China, sold under Shunhongyu, priced on request against your quantity.

When a 12 mm tool starts to slip there are two bad answers — run on and scrap the panel, or pull the spindle and lose the shift. The third answer is a collet:

• Reorder by number, not by caliper. The SKU says ER40 12MM, so the next collet is named on the order instead of measured off a worn one on the bench.
• The spring is the wear surface. Alloy spring steel is what brings the bore back to size after each nut release, so clamping stays a property of the part and not of who is tightening it.
• Grip around the shank, not on three jaws. The bore closes on the full circumference, which is why a 12 mm bit stays on the spindle axis instead of being held off it at one point.
• One nut, one collet, one change. There is no adapter and no key to fit, so the changeover is the nut and the machine goes back into the cut.
• Only the wear part is spent. A worn collet is one item to replace; the nut, the chuck and the spindle keep their position and their datum.
• The two deciding figures are in the name. ER40 and 12 mm are printed in the SKU, so a wrong-body or wrong-bore order is caught at the keyboard, before it ships.

Only if the spindle takes an ER40 nut. The collet is the ER40 body size with a 12 mm bore, so two conditions have to be true at once — an ER40 nut on the machine and a tool with a 12 mm nominal shank. Check the nut first, then the shank.

No — this is a 12 mm collet, not a range. The item is stated as one bore, 12 mm, for a 12 mm nominal shank, so a 10 mm or 6 mm bit needs the collet of that size instead.

Alloy spring steel, in one piece. That is the material a collet needs: it compresses when the nut closes on it and springs back when the nut is released, change after change, with no separate jaws or inserts to wear against each other.

Woodworking CNC machine tools. The listed application is tools for woodworking CNC machines — routers, boring heads and drilling units — wherever a 12 mm shank tool is held in an ER40 nut.

Not in this item. What is described is the collet itself — ER40 body, 12 mm bore, alloy spring steel — so the nut is the one already on your spindle; ask for a nut separately if you want a spare on the shelf.

No. The collet is a wear part and it is replaced on its own. The nut, the chuck and the spindle stay where they are and keep their datum, which is why a worn collet is a one-item purchase rather than a rebuild.

Keep the bore and the seat clean. Wood dust and resin pack into the slots and the bore between changes — wipe them out and seat the collet fully in the nut before the tool goes in, so the clamping faces meet metal on metal.

Price on request. Send the SKU ER40 12MM and the quantity, and the quote comes back against that part number; no fixed price is printed on the page.