What is the smallest possible reading in mm on the thimble scale what is the biggest possible reading?

The smallest possible reading on the thimble scale is typically determined by the smallest increment marked on the scale, often 0.01 mm. The biggest possible reading is the maximum value indicated on the thimble, which can vary depending on the specific instrument but is often around 1.0 mm or higher, depending on the design. Thus, the range of readings is defined by the instrument's scale limits.