When selecting the correct collet size for a given tool shank diameter, it is important to consider the nominal diameter and clamping range of a collet. For example, an ER collet with a nominal diameter of 10mm might have a clamping range of 1mm, meaning it could hold a tool between 9 and 10mm in diameter. It is best for the tool diameter to be as close as possible to the nominal diameter of the collet, i.e. put a 10mm tool shank in a 10mm collet. The closer to the bottom of a collets clamping range, the less effective it may be. It is also important to note that a collet cannot hold a tool larger than its nominal diameter, only smaller.
Learn more about our precision-engineered ER collets.