<P> The spindle of a micrometer graduated for the Imperial and US customary measurement systems has 40 threads per inch , so that one turn moves the spindle axially 0.025 inch ( 1 ÷ 40 = 0.025 ) , equal to the distance between adjacent graduations on the sleeve . The 25 graduations on the thimble allow the 0.025 inch to be further divided , so that turning the thimble through one division moves the spindle axially 0.001 inch ( 0.025 ÷ 25 = 0.001 ) . Thus , the reading is given by the number of whole divisions that are visible on the scale of the sleeve , multiplied by 25 ( the number of thousandths of an inch that each division represents ) , plus the number of that division on the thimble which coincides with the axial zero line on the sleeve . The result will be the diameter expressed in thousandths of an inch . As the numbers 1 , 2 , 3 , etc. , appear below every fourth sub-division on the sleeve , indicating hundreds of thousandths , the reading can easily be taken . </P>
<P> The spindle of a micrometer graduated for the Imperial and US customary measurement systems has 40 threads per inch , so that one turn moves the spindle axially 0.025 inch ( 1 ÷ 40 = 0.025 ) , equal to the distance between adjacent graduations on the sleeve . The 25 graduations on the thimble allow the 0.025 inch to be further divided , so that turning the thimble through one division moves the spindle axially 0.001 inch ( 0.025 ÷ 25 = 0.001 ) . Thus , the reading is given by the number of whole divisions that are visible on the scale of the sleeve , multiplied by 25 ( the number of thousandths of an inch that each division represents ) , plus the number of that division on the thimble which coincides with the axial zero line on the sleeve . The result will be the diameter expressed in thousandths of an inch . As the numbers 1 , 2 , 3 , etc. , appear below every fourth sub-division on the sleeve , indicating hundreds of thousandths , the reading can easily be taken . </P>
the value of one thimble scale division in a micrometer is
the value of one thimble scale division in a micrometer is
0.001 inch ( 0.025 ÷ 25 = 0.001 )
0.001 inch ( 0.025 ÷ 25 = 0.001 )