Screw Gauge Simulator

This micrometer screw gauge simulator is a free online tool for practising how to read a micrometer. It supports both SI (metric) and Imperial (inch) micrometers as fully independent instruments. In SI mode, the micrometer has a 0.01 mm least count with 50 thimble divisions. In Imperial mode, a standard 0.001″ least count micrometer with 25 thimble divisions is used. Four modes — Simulate, Explore, Practice, and Quiz — guide you from learning theory to hands-on measurement mastery.

The simulator opens in Simulate mode with SI units and the micrometer set to a default reading. To begin:

• Drag the thimble left or right to change the measurement. Use arrow keys for fine step adjustments, or Shift+arrow for half-revolution steps.
• Watch the readout badges and info row update in real time — they show the reading, MSR, CSR, LC, and the full TR formula.
• Toggle SI / Imperial to switch between a metric micrometer (0–15 mm) and an inch micrometer (0–1″). The entire scale redraws with correct divisions.
• Use the Zoom button (or press Z) to magnify the reading area where the thimble meets the barrel.

In Simulate mode the micrometer responds freely to dragging. As you rotate the thimble, observe how the barrel exposes or covers the scale marks, and how the thimble division aligns with the datum line. Audio feedback provides subtle click and tick sounds as you drag. The formula panel shows the step-by-step calculation live. Use this mode to build confidence before moving to Practice.

Explore mode is a reference library of micrometer concepts, organised into four categories:

• Micrometer Types: Outside, Inside, Depth, and Digital micrometers — learn the differences, ranges, and applications.
• Least Count: Worked examples for metric (0.01 mm) and imperial (0.001″) with the LC formula.
• Zero Error: No error, positive error, and negative error with correction formulas and procedures.
• Reading Method: Step-by-step guide — read MSR, find CSR alignment, calculate TR, avoid common errors.

Click any card in the grid to view its detailed information panel below.

Practice mode: Click Play to animate the micrometer to a random position, then Pause to stop. Read the scales and type the total reading (in the current unit). Click Check for instant feedback with sound. Click New for the next challenge. Your running score is displayed.

Quiz mode: A sequence of 5 questions tests your reading accuracy. After submitting all answers, a results panel shows your score with star ratings and a row-by-row breakdown. Quizzes work in both SI and Imperial modes.

The micrometer reading has two components:

• MSR (Main Scale Reading): In SI, count the whole and half-mm marks on the barrel. In Imperial, count the 0.025″ marks.
• CSR (Circular Scale Reading): The thimble division aligning with the datum line. Multiply by the LC.

SI example: Barrel shows 5.5 mm, thimble reads 23 → TR = 5.5 + (23 × 0.01) = 5.73 mm.

Imperial example: Barrel shows 0.275″, thimble reads 14 → TR = 0.275 + (14 × 0.001) = 0.289″.

This simulator includes two fully independent instruments:

• SI (Metric): Pitch = 0.5 mm, 50 thimble divisions, LC = 0.01 mm, range 0–15 mm.
• Imperial (Inch): Pitch = 0.025″, 25 thimble divisions, LC = 0.001″, range 0–1″. Barrel divided into 40ths of an inch.

Toggle between them using the SI / Imperial pills. The entire scale, tick marks, labels, readouts, formula, and practice/quiz answers update automatically.

• Always check for zero error before measuring — close the spindle onto the anvil and verify the reading is exactly 0.00 mm (or 0.000″).
• Use the ratchet stop (on a real micrometer) to apply consistent measuring force.
• Pay careful attention to the half-millimetre mark (SI) or the 0.025″ mark (Imperial) — missing it causes a 0.5 mm or 0.025″ error.
• Practice with both unit systems to prepare for different micrometers in exams and industry.
• Use Explore mode to review theory and formulas before attempting Practice or Quiz.
• The readout badges below the canvas give you a quick glance at key values without scrolling.