Guide · Collets and collet nuts
Seating an ER collet and bit: what the makers say
Power off, snap the collet into the nut, insert the bit deep enough and use the right size. ER collet installation as Carbide 3D, REGO-FIX and OSHA describe it.
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Picks that fit
- Genmitsu ER11 precision spring collet set, 7 or 15 pieces (1‑7 mm; 15‑piece adds 1/8 in and 1/4 in)Check price on Amazon
- Genmitsu ER11‑A collet clamping nuts, 4‑pack (M14 thread)Check price on Amazon
Short answer
Disconnect power, snap the collet into the nut until it clicks into the retention lip, then thread the nut on loosely and slide the bit in. Insert the shank over the full collet length where possible and never less than two-thirds of it.[1] Use a collet sized for the shank, never a smaller one, and tighten with the maker's wrenches.
Picks that fitAll picks and how to choose
- Genmitsu ER11 precision spring collet set, 7 or 15 pieces (1‑7 mm; 15‑piece adds 1/8 in and 1/4 in)Check price on Amazon
- Genmitsu ER11‑A collet clamping nuts, 4‑pack (M14 thread)Check price on Amazon
1. Power off
CCOHS router guidance says to disconnect the power supply before making any adjustments or changing bits.[2] On a CNC that means the spindle or router supply, not just pausing the job. Follow your machine maker's lockout instructions.
2. Pick the right collet
Choose the collet sized for the bit's shank. REGO-FIX advises never clamping a shank larger than the collet's nominal size; its example is a 12-11 mm collet, which must not clamp a 12.2 mm shank. Use the next larger collet instead.[1]
This matters most with inch bits in metric collets. A 1/4 inch shank is 6.35 mm, so a 6 mm collet is too small. Use a 1/4 inch collet. See ER11 vs ER16 vs ER20 for size tables.
Picks that fit1 product
For an ER11 spindle running inch bits, choose the 15-piece set (101-63-ER11), which includes 1/8 in and 1/4 in collets; the 7-piece set has metric sizes only.
ER11 set with metric and inch sizes
Genmitsu ER11 precision spring collet set, 7 or 15 pieces (1‑7 mm; 15‑piece adds 1/8 in and 1/4 in)
3. Snap the collet into the nut first
Carbide 3D explains that the off-center lip inside an ER nut is a retention feature that traps the collet, so the collet comes out of the spindle taper with the nut.[4] For that to work, the collet must be snapped into the nut before a tool goes in. A tool already in the collet keeps it from seating in the retention ring.[4]
Carbide warns that a collet that is not seated can be pushed off-center and damage the spindle and the collet. If the collet stays behind in the spindle when you remove the nut, it was not seated in the lip.
4. Insert the bit deep enough
With the collet and nut started on the spindle, slide the bit into the collet. REGO-FIX advises inserting the tool over the full collet length where possible and never less than two-thirds of the collet length.[1] Check that the cutting part of the bit, not the shank, sticks out where it needs to, and plan the job's depth around that.
5. Tighten with the right wrenches
Use the wrenches the spindle maker supplies. Carbide 3D's 65 mm ER16 guide, for example, lists a 22 mm wrench for the collet nut and a 16 mm wrench for the spindle shaft.[5] Makers differ on how much to say about torque. REGO-FIX recommends tightening its clamping nuts with a torque wrench and publishes its tightening torques separately.[6] PreciseBits cautions that its torque values may not always be required, preferable or even possible, and treats maximum torque as a warning.[7]
We give no torque figure of our own. Follow the spindle maker's instructions, and the nut maker's values where it publishes them.
Picks that fit1 product
Spare ER11-A nuts with a 14 mm thread. Choose them only if your ER11 spindle takes the standard M14 nut, not the M13 mini nut.
Genmitsu ER11‑A collet clamping nuts, 4‑pack (M14 thread)
6. Respect the speed limits
OSHA's router guidance says tools can be flung from the cutter head when they are poorly fastened, when the wrong tool is used or when tool speed is too high, and it advises securing tools properly in the holder.[3] It also advises labeling cutting tools and holders with their maximum permissible spindle speed.[3]
If a bit or collet has no stated speed rating, ask its maker before running it fast. A collet that grips the shank does not raise the bit's speed limit.
Next
Questions
How far should a bit go into an ER collet?
REGO-FIX advises inserting the tool over the full collet length where possible and never less than two-thirds of the collet length.[1]
Why won't my collet come out with the nut?
It was probably not snapped into the nut's retention lip. Carbide 3D says the off-center lip traps the collet so it leaves the taper with the nut, and that the collet must be snapped in before the tool goes in.[4]
Can I use a 1/4 inch collet for a slightly oversize shank?
No. REGO-FIX advises never clamping a shank larger than the collet's nominal size and using the next larger collet instead.[1]
How tight should the collet nut be?
We give no torque figure. REGO-FIX recommends a torque wrench and publishes its values; PreciseBits cautions that its torque values are not always required or possible. Follow your spindle maker's instructions.[6][7]
Do I need to unplug the machine to change a bit?
CCOHS router guidance says to disconnect the power supply before making any adjustments or changing bits.[2]