Collet FORTIS ER40 FI 25 - 24 DIN6499, ER40 milling/chuck collet for 25 mm shank

FORTIS ER40 FI 25 - 24 DIN6499 is an ER40 series collet designed to clamp 25 mm diameter shanks or tools. Manufactured to the DIN 6499 specification, this collet offers precise concentricity and stable retention for milling, drilling and CNC machining operations. The collet fits standard ER40 toolholders and chucks, making it suitable for use in metalworking shops and production environments where secure and repeatable tool clamping is required.

Advantages

The collet provides consistent radial accuracy and balanced clamping force across the 25 mm shank, reducing runout and improving surface finish. Its compliance with DIN 6499 ensures dimensional compatibility with ER40 systems and simplifies tool changes. The solid construction offers wear resistance and long service life under normal machining conditions, while the design supports secure gripping of cylindrical shanks without additional adapters.

Suitable for

• Clamping 25 mm diameter end mills, drills and reamers in ER40 toolholders
• CNC milling and drilling operations requiring repeatable concentricity
• Bench and production lathes or milling machines with ER40 collet chucks
• Workshop applications where quick tool changes and reliable retention are needed

When it may not be suitable

This collet is intended specifically for cylindrical shanks with a nominal diameter of 25 mm. It is not suitable for non-cylindrical tool shanks, tapered tooling, or applications that require integrated coolant through the spindle if the collet design does not support it. For jobs requiring tool-holding standards other than ER40 or for larger/smaller diameters, a different collet size or system will be necessary.

Key specifications

• Series: ER40
• Clamping diameter: 25 mm (nominal)
• Standard: DIN 6499
• Material: hardened steel (manufacturing standard material for ER collets)
• Application: milling, drilling, CNC machining

How to use

Insert the 25 mm tool shank into the collet and assemble the collet into a compatible ER40 nut and holder according to the toolholder manufacturer’s instructions. Tighten the nut to the recommended torque to achieve secure clamping and correct concentricity. For repeatable results, ensure the tool shank and collet contact surfaces are clean and free of chips or contamination before assembly. Regularly inspect the collet for wear and replace if deformation or excessive runout is detected.

What to consider before purchase

• Verify that your toolholder or chuck accepts ER40 collets and supports a 25 mm clamping diameter.
• Confirm the required concentricity and runout tolerances for your machining tasks.
• Check material and hardness requirements based on the tooling and operational loads.

Usage recommendations

Use the collet with properly maintained ER40 nuts and holders, apply manufacturer-recommended torque values, and keep clamping surfaces clean. For critical high-precision work, verify runout after clamping and replace collets showing wear to maintain machining accuracy.