An ER collet chuck is a tool holder that uses a collet and a nut to grip the shank of a cutting tool. Choose its machine-side taper or shank first, then the ER series, individual collet size and holder length. The ER size alone does not tell you whether the chuck fits your machine.
What parts do I need?
Part
What it does
BVF product to check
Chuck body
Connects to the machine and contains the tapered pocket for the collet.
Check what is supplied with the selected chuck. A collet, spanner or pull stud may need to be ordered separately.
BT40, BBT40 or straight shank?
BT40: choose this machine-side taper when the machine specification calls for BT40. A conventional BT40 holder seats on the taper.
BBT40: BVF describes this as dual contact at the face and taper, also called UBT40. Check whether the machine spindle supports dual contact before choosing the BBT-40 ER-32mm Collet Chuck.
Straight or cylindrical shank: select the shank diameter and length to suit the receiving holder. BVF's ER32 UM cylindrical chuck lists 25, 32 and 40 mm shanks. Those numbers describe the chuck's machine-side shank, not the cutting tool's shank.
Confirm the spindle or receiving-holder specification from the machine documentation. For BT40, also confirm the pull stud: BVF lists 45, 60 and 90 degree versions, each with or without a hole. Choose the version specified for the machine.
How do I choose the ER size?
Match the ER series across the chuck, collet and nut. Then measure the cutting tool shank and select a collet whose individual range contains it. ER32 is a series name; it does not mean a 32 mm tool shank fits.
BVF's ER32 collet listing covers nominal sizes from 1 to 20 mm. A 10 mm collet with a 1 mm collapse range covers 9 to 10 mm. For other series and small-bore exceptions, use the ER collet sizes chart.
What do 70L, 100L and 150L mean?
In BVF's BT40 and BBT40 chuck listings, these options mean L = 70, 100 and 150 mm. In a tapered collet chuck drawing, gauge length is the distance from the spindle reference plane, or gauge line, to the front face of the collet nut. It describes holder projection before adding the tool's protruding length.
BVF's listing text calls L the length but does not give a drawing confirming its endpoints. Check the drawing before treating L as an exact gauge length. Choose the shortest holder that provides the required reach and clears the workpiece and fixture; longer tools and holders are less stable.
Usual order of assembly
Clean the collet and check that its slots are clear.
Angle the collet into the nut so its extraction groove engages the eccentric ring. Snap it into place before putting the assembly into the chuck.
Screw the nut and seated collet onto the chuck body.
Insert the tool shank within the selected collet's range, then tighten the nut. Follow the holder maker's insertion and tightening instructions; use its specified torque with suitable torque equipment.
For a BT40 holder, confirm the machine-specified pull stud and installation instructions before fitting the holder into the spindle.
