// measurement · least count 0.01 mm

Screw Gauge

Drag the thimble — or use ← → keys (Shift for 1 mm)
magnified view
Spindle gap
Zero error 0.00 mm
View

Bring the spindle to the anvil to inspect zero error, then measure the wire.

How to read a screw gauge

  1. Least count. One full turn of the thimble advances the spindle by the pitch, 1 mm. The thimble carries 100 divisions, so LC = 1 mm ⁄ 100 = 0.01 mm.
  2. Main scale reading (MSR). The last millimetre mark still visible on the sleeve, just left of the thimble edge.
  3. Circular scale division (CSD). The thimble division that sits exactly on the sleeve's reference line. Use the magnifier!
  4. Observed reading = MSR + CSD × LC.
  5. Zero error. Close the gap fully. If the reference line shows a small division (like 4), the error is positive: ZE = +4 × LC. If it shows one near 100 (like 96), it's negative: ZE = (96 − 100) × LC.
  6. Corrected reading = observed − ZE (mind the sign — subtracting a negative adds).
💡 In Explore mode, drag the thimble and watch the reading panel update live. Arrow keys turn it by one least count.