Overview
A collet is a slotted metal sleeve that grips a tool shank or round workpiece when pulled into a tapered seat. It provides uniform clamping around the held diameter and is one of the most important elements for tool holding accuracy. Collets directly affect vibration control, surface finish quality, and tool life in machining operations of all types.
Types and Features
ER series collets are the worldwide standard for CNC tool holding. They come in sizes from ER8 up to ER50 and cover shank diameters from 1 to 34 millimeters. Each collet has about one millimeter of clamping range. TG collets are made to tighter tolerances with extra precision grinding, achieving runout under 0.003 mm. Sealing collets have built-in seals for use with coolant-through tool systems. Soft emergency collets can be bored to any custom size for special applications.
How to Choose
Pick the collet series that matches your tool shank diameter. The shank should fall near the middle of the collet clamping range for the best grip and accuracy. Always match the collet taper to your specific chuck body because mixing different series leads to poor seating. For fine finishing work, choose TG or premium collets. High-speed work needs well-balanced collets to avoid vibration problems.
Replacement and Installation
Take off the collet nut and tilt the old collet out at an angle. Clean the nut inside, the chuck body taper, and the new collet surfaces thoroughly. Put the new collet into the nut at an angle until the extraction ring engages, then push it upright. Screw the nut on, put in the tool, and tighten to the stated torque value. Do not overtighten because that can distort the collet and increase runout.
Maintenance Tips
Clean each collet after use to remove fluid, oil, and tiny metal particles from the taper and bore. Use a brush to clear the slots where debris collects. Look for wear signs like bore enlargement, scratches on the taper, or cracks near slot ends. Keep collets in a case that prevents them from touching each other. Lightly oil them before storage and plan to replace your most-used collets every six to twelve months.
