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The ER System is the most versatile toolholding system for any operation utilising a round shank cutting tool in a machining or turning centre. This includes drilling, milling, tapping, reaming and boring. ER Collets are available in the following series ranges to maximise efficiency in most applications:

  • ER8   1mm-5mm in 0.5mm steps
  • ER11  1mm-7mm in 0.5mm steps
  • ER16  1mm-10mm in 1mm steps
  • ER20  2mm-13mm in 1mm steps
  • ER25  2mm-16mm in 1mm steps
  • ER32  3mm-20mm in 1mm steps
  • ER40  4mm-26mm in 1mm steps

The ER system is the only popular toolholding system in which all components (chuck, collets and clamping nut) are standardised by DIN 6499.

ER systems are truly interchangeable. All manufacturers of this system should conform to the DIN 6499 standard. This becomes important to users that may have toolholding systems from different toolholding system manufacturers.

As tools are taken out of the tool crib and reassembled for different jobs, if all the ER system components are in good condition, and are from quality toolholding system manufacturers, the collet and tool should achieve the DIN 6499 accuracy.

When using round shank cutting tools, collets and collet chucks centralise the cutting tool and this should result in increased tool life, higher feed rates, better workpiece accuracy and enhanced workpiece finish.


1. Insert collet into nut at angle as shown to engage extraction tongue in groove of collet.

2. Screw nut onto collet holder with collet securely in nut.3. Insert tool to be gripped and lock nut.

IMPORTANT: Never screw nut onto collet unless collet is properly seated in nut.

Hold nut in vertical position and remove nut at an angle. Collet is automatically withdrawn from chuck by eccentric ring of nut when unscrewed.

The chuck, collet and nut must be thoroughly cleaned before assembling to maintain accuracy.

The collet must be installed into the nut (see assembly instructions) before engagement with the collet chuck to ensure the collet is seated into the 30 degree concave angle of the nut. Putting the collet into the chuck and then installing the nut will result in a condition that the eccentric ring of nut will engage only one side of the collet and produce poor results such as runout and drastically reduced holding strength.

ER Collets are designed to collapse 1mm (except ER8 & ER11 – collapse 0.5mm).

ER Collets must be tightened correctly. Many engineers have been trained that nothing is ever too tight. This is particularly not true with collets and collet chucks. Over tightening a collet chuck will distort the collet and actually diminish the holding strength and accuracy.

Cutting tools should be inserted into the collet the full length of the bore wherever possible. Failure to insert the cutting tool into at least 2/3 of the bore may distort the collet.

Collets should be cleaned and oiled prior to storage.
ER Collets are also very economical when compared with other popular collet systems. Collets work best when used at nominal or full diameter but when economy is desired this system compares very favourably with other systems.


See our full range of ER collets here

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