A few nice cnc lathe parts pictures I located:
Lathing new PTFE holder for RepRap
Image by wizard23
The PTFE holder kept slipping out so we designed a new one particular that has a T-profile to avert the slipping. The upper component is about 21mm (that was the nearest diameter we could get PTFE rods in vienna) and the decrease part is the classic RepRap PTFE holder as described on the wiki (despite the fact that we enhanced the diameter to 16.9mm to compensate for the worn out molded clamp element).