The DF-1 differential micrometer head from Del-Tron Precision Inc. can be mounted to linear slides or stages to position cameras, lenses, part locators and other devices requiring precision alignment. Coarse adjustment is achieved using a knurled ring operating a 40-pitch screw that moves the spindle 0.025 in. per revolution while an adjusting thimble provides fine adjustment of 0.004 in. per revolution. The spindle, locked to the innermost ring, has a hardened ball at its end to reduce friction and wear. Other features include overall reduction from 254 to 1 and total coarse movement of 1/4 in. The positioner is suitable for use with precision laboratory instruments, optical devices and production machinery.