Item Description:
Starrett T221XL Hi-Precision Micrometer 0-1” / .0001” / Inner & Outer ThimblesComes as pictured.How it works:“The inner thimble is graduated in .001 divisions, the outer thimble is graduated in .0001 divisions. You use the outer thimble to move the spindle up to the work, at this point both the inner and outer thimbles are turning together. The outer thimble’s graduations start at 0 then 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, for a total of 4 times. You bring the thimbles up until the anvils contact the work. At this point the inner thimble stops turning and the outer one continues to turn. 1/4 turn of the outer thimble moves the spindle .001 of an inch. After making contact you turn the outer thimble 10 divisions this will put a pressure of a known force on the spindle, you then back up the outer thimble up until the .001 line on the inner thimble lines up with a whole number line on the sleeve. You direct read the .0001 of the outer thimble.”
