ER Collets

An ER collet is a DIN 6499 spring collet: its slotted taper closes evenly around a shank as the collet nut is tightened, so one collet grips a small range of diameters instead of needing an exact match for every tool. We stock the ER8 to ER50 range, in standard and ultra precision, coolant sealed, tapping and imperial specifications.

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Standard ER Collets
10 micron run-out collets in ER8 to ER50, the everyday choice for general milling and drilling.
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Ultra Precision ER Collets
5 micron run-out, half the run-out of our standard collets, for finishing passes and thread milling where tool deflection shows up in the surface finish.
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Standard Coolant Sealed ER Collets
Standard precision collets with a sealing ring built in, so through-spindle coolant is directed at the cutting edge instead of leaking out around the collet body.
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Ultra Precision Coolant Sealed
The same coolant seal paired with 5 micron ultra precision run-out, for finishing operations that also need coolant delivered straight to the cutting edge.
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ER Tapping Collets
Made to hold tap shanks rather than round cutter shanks; a square drive engages the tap's flat so it can't spin in the collet under load.
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Imperial ER Collets
The same ER collet in inch sizes, 1/8" to 3/4", for imperial-shank tooling and machines set up to imperial standards.
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Quick Change ER Tapping Collets
Rigid tapping collets in a quick-change fitting, so taps can be swapped without pulling the holder from the spindle mid-cycle.
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ER Jet Coolant Sealed Collets
Directs coolant around the outside of the cutter through jets in the collet body, useful for tools without a through-coolant bore.
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ER Collet Sets
Standard precision collets boxed as a full run of sizes, 10, 15 or 18 pieces covering the ER16, ER25 or ER32 range, so you're not ordering collets one size at a time.
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ER Collet Nuts
Mini, castellated and hexagon nuts for ER16 to ER50; the nut draws the collet into its taper and is worth replacing on its own if the register wears.
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ER Collet Wrenches
Matched to nut type, castellated spanners for castle (UM) nuts, mini spanners for mini nuts, so the wrench seats properly instead of slipping under torque.
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ER stands for the DIN 6499 collet standard — a spring collet that closes evenly around a shank when the collet nut is tightened, giving good concentricity across a range of diameters rather than needing one collet per exact size like a 5C. The size number (ER8 through ER50) refers to the collet's outside diameter, not the clamping range, and determines which collet chuck or toolholder it fits.

ER32 is the size most jobbing shops reach for first — it's the standard fit for BT30 and BT40 toolholders and covers roughly 2-20mm clamping range across the full collet set, which handles the majority of cutter and workpiece shanks on a typical mill. ER16 and ER20 suit smaller BT30 setups and lighter-duty spindles; ER40 and ER50 are for larger shanks and heavier cuts.

Standard precision collets (around 0.010mm TIR) cover general milling and drilling. Ultra precision (0.005mm TIR or better) is worth the extra cost for finish milling, thread milling or anything where tool runout shows up in the surface finish. Coolant sealed versions add a seal ring so through-spindle coolant reaches the cutting edge instead of leaking out around the collet.

See the full ER Collets range for all sizes and grades in stock, or our collet buying guide if you're not yet sure ER is the right system for your machine.