I need a special tool ?
Has anyone any suggestions for a tool which would be "like" a camera iris, with a hole several mm long, but which can be varied in diameter from 1 (0.040 ") to 0.2mm (0.008"). I need to set the diameter fairly carefully, to just gently pinch a bundle of 70micron (0.0029"") optical fibres passed down the centre. The hole needs to be very circular and rigid, even as its closing......
Something kind of like the mechanism of a "pin-chuck" suggests itself, but wouldn't be very round in the limit.
Any ideas ?