In article <000701c1e1ff$7e082e60$0100a8c0@KAIROS>, Ernst Dinkla <E.Dinkla@chello.nl> writes >The carrier is inserted in a traction unit that positions the >carrier for scanning etc with the gear teeth at the side of the >carrier. For scanning the whole traction unit glides on two rods >with a traditional 3 point brass bearing setup. That movement is >done with a finely machined screw spindle (don't know the right >English term for it). A "worm drive"? That is frequently used when relatively large rotational motion, such as from a motor, need to be converted into fine linear movement. A derivative is the "worm gear", used to achieve very low precision gearing ratios, where the driven linear unit is replaced with a concavely curved toothed wheel. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's pissed. Python Philosophers - Turn off HTML mail features. Keep quoted material short. Use accurate subject lines. http://www.leben.com/lists for list instructions.