The outside micrometer has a range of 75 to 100 mm, which means that the maximum reading it can give is 100 mm and the minimum reading is 75 mm.
The least count of the micrometer is given as 0.01 mm. This means that the smallest measurement that can be read on the thimble scale is 0.01 mm.
To read the value on the micrometer, we need to add the value on the barrel scale (i.e., the main scale) to the value on the thimble scale.
In this case, the barrel reading is 15.50 mm, and the 10th thimble graduation coincides with the barrel datum line. This means that we need to add 0.9 mm (since 9 thimble graduations have passed the datum line) to the barrel reading to get the total measurement.
The reading is:
15.50 mm + (0.9 x 0.01 mm) = 15.59 mm
Therefore, the reading on the outside micrometer is 15.59 mm.
This reamer has tapered cutting edges for reaming taper holes to suit taper pins. A taper pin reamer is made with a taper of 1 in 50. These reamers are available with straight or helical flutes.