Vortex 5C Metric Lathe collet - Square - 8mm13 15 Micron Runout 5C Emergency Collets are soft and can be bored to size depth taper shape to suit a particular component. Pins are fitted to keep the collet 'open' during the boring operation which is carried out in a 5C lathe collet chuck. When no longer required, 5C emergency collets can be re bored many times over to hold larger parts (so don't throw the pins away!).