50mm 3-jaw scroll chuck, reversible jaws, T-bars, M12 x 1
 
The MM50 is a miniature engineering chuck three jawed, self-centring and a scroll chuck just like a full size engineering chuck.  But it is just 50 millimetres in diameter!  To keep the size minimal, the chuck is operated by two miniature tommy bars.  The interesting feature is that the three stepped jaws are reversible to make the chuck functionally equivalent to a set of internal and external engineering jaws.  This means that the chuck will grip in both compression and expansion modes giving a wide range of workholding possibilities.  Being three-jawed, the chuck centres any circular work perfectly.  The minimum hold diameter is next to nothing - should we say 0.5 mm for the record?