“The TIR of the drill being held in my ER collet is excessive. What TIR can I expect from a standard ER collet?"

• Quick fix — if you are using a ball bearing cap on your ER holder, change it to a one piece cap. The ball bearing cap allows you to use more torque when gripping solid floating tap collets, but when used for drilling, the TIR is not as accurate as the one-piece cap.
• All of our ER collets are made to the DIN 6499 specification. Refer to page 12 for the acceptable TIR for your collet. When checking the collet and holder, use a certified gauge plug. First, indicate the seat of the holder, then assemble collet and gauge plug and indicate the plug at the “L" dimension. Make corrections for holder seat runout (the most accurate check is to use a coordinate measuring system – most indicators do not give a true reading when rotating 360° from the lathe spindle). If this checks out within specifications, check the gauge pin at the actual drill length, which may be longer than the “L" dimension. If the TIR at this point is too great, you will have to acquire a higher precision collet such as the ERNC. If you’re using a metric bushing to hold a fractional drill, a more reasonable solution would be to acquire an inch series collet for the exact shank of your drill. “I am using an ER Collet in a high-speed spindle and am getting vibration that I don’t get with my other holders. What’s wrong?"
• You’re probably using a standard one-piece cap. Acquire a one-piece cap that has a ring to hold the collet instead of the standard cap that has an eccentric slot. The eccentricity of the groove will cause an out-of-balance condition at high rpm. If this does not eliminate the vibration, the complete assembly will have to be precision balanced in relation to the RPM you’re running.