ER40 Spring Collet ER Clamping Collets For Woodworking CNC Milling Machine Parts

An ER40 spring collet is the slotted sleeve that lets one spindle hold nine different tool shank diameters. This one is made of stainless steel and comes in 3, 3.175, 4, 5, 6, 8, 10, 12 and 12.7 mm bores, so 1/8 in and 1/2 in router bits fit without an adapter. The same collet pattern is also stocked in ER11, ER20, ER25 and ER32. Each collet ships individually in a plastic tube with an installation instruction; samples are available.

A shop running several router tools runs into the same two problems: a drawer of chucks that never quite fit the shank in hand, and a cutter that creeps in its holder mid-pass. The ER40 spring collet removes both. It is a slotted stainless steel sleeve that the collet nut squeezes onto the shank, so the tool is centred by the collet bore, not by three jaws.

This is an ER clamping collet, not a drill chuck. Slots cut in from both ends let the nut close the bore evenly along its full length. That distributed grip is what stops a 1/2 in router bit walking in the cut, and it is why one ER body serves milling spindles, router tables and engraving heads.

Nine ER40 bores are listed: 3, 3.175, 4, 5, 6, 8, 10, 12 and 12.7 mm. The 3.175 mm and 12.7 mm sizes match 1/8 in and 1/2 in shanks, so inch tooling needs no adapter. Smaller spindles take the same pattern in ER11, ER20, ER25 and ER32, one collet system for the whole shop.

Each collet ships individually packed in a plastic tube, with an installation instruction in the package. Samples are available, so one bore can be tried on the real spindle first, and price is quoted per order. Body material is stainless steel across the ER40 range.

Bore count, slot pattern and packing decide whether a tool change costs two seconds or a scrapped part.

• Nine bores from 3 to 12.7 mm — 3, 3.175, 4, 5, 6, 8, 10, 12 and 12.7 mm; the shank diameter picks the order.
• Slots cut from both ends — the slot pattern alternates in from each face, so nut pressure closes the bore along its whole length instead of pinching it.
• Stainless steel body — the collet is machined from stainless steel, the material listed for every size in the ER40 range.
• Inch shanks without adapters — 3.175 mm takes 1/8 in tooling and 12.7 mm takes 1/2 in tooling, 2 imperial sizes covered directly.
• Same system in 4 smaller sizes — ER11, ER20, ER25 and ER32 load the same way, so a spindle change is not a new habit.
• Tool change by nut only — loosen the nut, swap the collet, tighten; no chuck key and no re-truing of three jaws.
• One collet per plastic tube — individually packed, so slot edges stay undinged between bench and spindle.
• Installation instruction inside — a printed sheet travels in the package, so first fitting needs no phone call.
• Sample before a full order — single collets can be ordered as samples against your own spindle.

The choice is usually between a cheap chuck that slips and a dedicated holder for every single tool. The ER40 is the middle path: one collet body, nine bores, and a changeover that is a nut rather than a setup.

• One bore per shank, nine bores in the range. A shop holding 1/8 in, 6 mm and 1/2 in tools keeps three collets instead of three chucks; the other 6 sizes wait on the shelf.
• Grip that is spread, not pinched. The slots let the whole sleeve close on the shank, so a profiling pass with a 12.7 mm bore bit is not carried by three jaw edges.
• The same routine on every spindle. ER11, ER20, ER25, ER32 and ER40 all load the same way, so a new operator learns one tool change and applies it everywhere.
• A spare that stores flat. One collet in one plastic tube, 9 tubes to a small drawer, instead of a rack of holders at several hundred grams each.
• Test cost is one collet. Samples are available, so the decision is made on your spindle with your cutter, not on a photograph.
• Quoted against the order, not guessed. Price follows the bore sizes and quantity on the order, so a mixed order of several sizes comes back as one figure.

An ER40 collet grips the whole shank; a drill chuck grips it at three jaw edges. The slots close the bore evenly along its full length, which is why a cutter held in it does not walk during a profiling pass.

Nine listed bores: 3, 3.175, 4, 5, 6, 8, 10, 12 and 12.7 mm. The 3.175 mm and 12.7 mm sizes take 1/8 in and 1/2 in shanks without an adapter.

It fits any spindle that takes ER40 collets, and CNC milling spindles, router tables and engraving heads all use this body. If your spindle is smaller, the same collet pattern comes in ER11, ER20, ER25 and ER32.

One collet per shank diameter, not per tool. Two cutters with the same shank share one collet, so a shop running 1/8 in, 6 mm and 1/2 in tooling needs three.

Stainless steel. The material is listed as stainless steel for the ER40 range, and the body is machined, with slots cut in from both ends.

Individually in a plastic tube, with an installation instruction in the package. One collet per tube keeps the slot edges undinged in transit.

Yes. Samples are available, so one bore can be tested on your own spindle with your own cutter before the quantity goes on an order.

Price is quoted per order, not fixed on the page. Send the bore sizes and the quantity and the figure comes back for that exact combination.