Screw Gauge and Pitch
The pitch is the axial distance moved in one complete rotation, and the screw-gauge least count is pitch divided by the number of equal circular-scale divisions; the corrected reading includes the signed zero correction.
Why this shows up in the exam
Wire diameter measurement · Sheet thickness measurement · Small displacement calibration
Learn the idea
A screw gauge converts rotation into small axial motion, with least count set by pitch divided by circular divisions. A screw is a spiral ramp: one full turn advances by one pitch, and the circular scale divides that advance into finer steps.
🧠 Memory hook: One turn moves one pitch; divide the pitch around the circle.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- pitch = axial advance/number of rotations — screw pitch
- LC = pitch/circular divisions — screw-gauge least count
- reading = pitch-scale reading + circular reading x LC + zero correction — corrected measurement
How to approach it
- 1Determine pitch from several turns if possible
- 2Compute least count
- 3Combine scales and apply zero correction
Common slip-ups that cost marks
- •Using diameter when pitch is requested
- •Confusing circular divisions with rotations
- •Applying zero error with the wrong sign
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A quantity Q is defined as Q = force^1 / speed^2. Which dimensional formula represents Q?
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