Re: Collet advice needed
Hi Gunda,
The majority of shops order the exact size collet they need, so if you're picking off on a 6mm diameter, you order a 6mm collet. This is most common for production runs because the collet is hardened and has a long life (if treated properly). You can also get carbide lined collets for longer life.
You can get "emergency" collets that are non-hardened material and have pins on the OD so that you can clamp the collet and bore it to any size desired. These are used less often because they are soft steel, so they dont hold up as long.
Also, if you dont need to bore all the way through the collet (for a short part), you can bore out a hardened collet to your desired size. Similarly, you can mill a shape into the collet for non-round pickoff. Just make sure to put a gage pin in the collet near the back of the bore so that the collet does not compress all the way when boring or milling, or else you wont be able to chuck on the part.
Extended nose collets are usually used for the Sub Spindle to allow better tool clearance.
I see you're in Bulgaria, but here in the US, the most common collet makers are Hardinge, Southwick and Meister, or Schlenker. They make collets for almost every machine.
CNC Product Manager / Training Consultant