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HoW to reAd A stArrett MIcroMeter

GrAduAted In tHousAndtHs of An IncH GrAduAted In ten-tHousAndtHs of An IncH
.001" .0001"
The pitch of the screw thread on the spindle is 40 threads per inch. Starrett micrometers graduated in ten-thousandths of an inch read like
One revolution of the thimble advances the spindle face toward or micrometers graduated in thousandths, except that an additional reading
away from the anvil face precisely 1/40" or .025 inches. in ten-thousandths is obtained from a vernier scale on the sleeve.
The reading line on the sleeve is divided into 40 equal parts by vertical The vernier consists of ten divisions on the sleeve, which occupy the
lines that correspond to the number of threads on the spindle. Therefore, same space as nine divisions on the thimble (Fig. B). Therefore, the
MicroMeters for easy reading. Every fourth line, which is longer than the others, and one of the nine spaces on the thimble is one-tenth of a division on
difference between the width of one of the ten spaces on the vernier
each vertical line designates 1/40" or .025 inches. Lines vary in length
the thimble, or one ten-thousandth (.0001").
designates a hundred thousandth. For example: the line marked "1"
represents .100" and the line marked "2" represents .200", etc.
To read a ten-thousandths micrometer, first obtain the thousandths
reading, then see which of the lines on the vernier coincides with a line
The beveled edge of the thimble is divided into 25 equal parts with
each line representing .001" and every line numbered consecutively.
thousandth, if it is the line marked "2", add two ten-thousandths, etc.
Rotating the thimble from one of these lines to the next moves the on the thimble. If it is the line marked "1" on the sleeve, add one ten-
spindle longitudinally 1/25 of .025", or .001". Rotating two divisions
represents .002", etc. Twenty-five divisions indicate a complete
revolution of .025" or 1/40 of an inch.
To read the micrometer in thousandths, multiply the number of vertical
divisions visible on the sleeve by .025", and to this add the number of
thousandths indicated by the line on the thimble which coincides with
the reading line on the sleeve.

FIG. 1

THIMBLE THIMBLE

SLEEVE THIMBLE

SLEEVE SLEEVE
FIG. B FIG. C
Reading .2500" Reading .2507"

Reading .178" FIGURE C – READING .2507"
The "2" line on sleeve is visible, representing ................................................... .200"
EXAMPLE:
There are two additional lines visible,each representing .025" ........................... .050"
The "1" line on sleeve is visible, representing ................................................... .100" The reading line on the sleeve lies between the "0" and "1" on the
There are 3 additional lines visible, each representing .025"; 3 x .025"............ = .075 thimble indicating that a vernier reading must be added .................................. ----
Line "3" on the thimble coincides with the reading line on the sleeve, The "7" line is the only line on the vernier that coincides with a line on
each line representing .001"; 3 x .001" .................................................. . = .003" the thimble, representing 7 x .0001" ..................................................... = .0007"
The micrometer reading is ............................................................................... 178" The micrometer reading is ............................................................................. .2507"

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