- Practice · 8 marks
Slip gauges: wringing and building a stack
Short answer
Slip gauges are precise length standards with flat parallel faces. Wringing is adhesion of clean wrung faces, forming stacks without error. Grades 00,0,1,2. Precautions: clean, avoid heat, use minimum gauges. To build 58.275 mm, eliminate last decimal: 1.005 + 1.27 + 6.0 + 50 mm (4 gauges).
What are slip gauges? Explain wringing, the grades of slip gauges and the precautions in their use. Build up a size of 58.275 mm from a set containing 1.005 mm; 1.001 to 1.009 mm in steps of 0.001 mm; 1.01 to 1.49 mm in steps of 0.01 mm; 0.5 to 9.5 mm in steps of 0.5 mm; and 10 to 100 mm in steps of 10 mm, using the minimum number of gauges.
Slip gauges (gauge blocks) are rectangular blocks of hardened, stabilised steel (or ceramic, tungsten carbide) with two opposite faces flat and parallel to a very high accuracy and a precise distance apart. They are the working end standards of length used to calibrate instruments, set comparators and sine bars, and for direct precision measurement.
Wringing
When two clean gauge faces are slid together with slight pressure and a twisting motion, they stick together. The adhesion is due to a thin film of oil or moisture (molecular attraction and atmospheric pressure). Wringing removes the air gap, so the length of the stack is the sum of the individual sizes with no measurable error. Gauges must be wrung just before use and separated soon after.
Grades (IS 2984 / BS 4311)
- Grade 00 (reference/calibration) for calibration laboratories.
- Grade 0 for inspection and master use.
- Grade 1 for workshop inspection and setting tools.
- Grade 2 for general workshop use and tool room.
Precautions
Keep at standard C and let the gauges soak; hold them with minimum contact so that body heat is not conducted; clean with a soft lint-free cloth and a solvent; wring correctly; coat with petroleum jelly or rust inhibitor after use; avoid dropping; use the minimum number of gauges to reduce cumulative error; use protector gauges at the end of stacks that are used for measuring.
Building 58.275 mm
Always eliminate the last decimal place first.
| Step | Gauge chosen | Remainder |
|---|---|---|
| Start | 58.275 | |
| 1 | 1.005 | 57.270 |
| 2 | 1.27 | 56.000 |
| 3 | 6.0 | 50.000 |
| 4 | 50 | 0 |
Check: mm.
Answer: 58.275 mm = 1.005 + 1.27 + 6.0 + 50 mm (4 gauges).
✓ Answer checked by Claude Opus 5.5 (high effort)
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