--- title: "Slip gauges: wringing and building a stack" subject: "Metrology" chapter: 4 key: "semester_3/metrology:slip-gauge-wringing-and-stack" source: https://www.bctengineer.com/q/semester_3/metrology/slip-gauge-wringing-and-stack site: BCT Engineering --- # Slip gauges: wringing and building a stack Metrology · Chapter 4: Linear Measurement - Asked in: year not given, 8 marks - Video: [How to Build a Stack of Gauge Blocks](https://www.youtube.com/watch?v=BGRU2fyQ7Uw) — Toms Techniques - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/metrology/slip-gauge-wringing-and-stack - Whole chapter: https://www.bctengineer.com/md/semester_3/metrology/chapter-4 ## Question 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. ## 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). ## Answer **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 $20^\circ$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: $1.005 + 1.27 + 6.0 + 50 = 58.275$ mm. **Answer: 58.275 mm = 1.005 + 1.27 + 6.0 + 50 mm (4 gauges).** ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why does a wrung slip gauge stack have a length equal to the sum of individual sizes? A. Wringing expands the gauges slightly B. Wringing removes the air gap, leaving only a thin film so there is no measurable error C. The gauges are welded together D. Wringing makes the blocks magnetic Answer: B. Wringing slides clean faces together so that a thin oil or moisture film holds them with no measurable air gap. (Key point: Wringing) 2. What is the rule when building a slip gauge stack by the minimum number of gauges? A. Start with the largest gauge B. Start with the smallest gauge in the set regardless of size C. Eliminate the last decimal place first D. Use only gauges ending in zero Answer: C. Always eliminate the last decimal place first, which is why 1.005 is chosen first for 58.275 mm. (Key point: Stack building rule) 3. Which stack correctly builds 58.275 mm with 4 gauges? A. 1.005 + 1.27 + 6.0 + 50 B. 1.005 + 1.27 + 7.0 + 49 C. 1.001 + 1.274 + 6.0 + 50 D. 1.005 + 1.27 + 6.5 + 50 Answer: A. 58.275 - 1.005 = 57.270; - 1.27 = 56.000; - 6.0 = 50.000; - 50 = 0. (Key point: Stack for 58.275) 4. Which is a correct precaution in using slip gauges? A. Hold them firmly for a long time to keep them warm B. Use as many gauges as possible for accuracy C. Clean with a lint-free cloth, soak at 20°C and coat with rust inhibitor after use D. Leave them wrung together after use Answer: C. Gauges should be at 20°C, handled minimally, cleaned, wrung just before use and protected from rust; the minimum number of gauges reduces cumulative error. (Key point: Precautions) 5. Which grade of slip gauge is intended for calibration laboratories? A. Grade 2 B. Grade 1 C. Grade 0 D. Grade 00 Answer: D. Grade 00 is the reference/calibration grade; grade 0 is for inspection and masters, 1 for workshop inspection, 2 for general workshop. (Key point: Grades) ## Related in Metrology - [Classify fits from given limits of size](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Aclassify-fits-from-limits) — Metrology, chapter 9 - [Sine bar principle, setting and error](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Asine-bar-setting-and-error) — Metrology, chapter 5 - [Least squares fit for calibration data](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Aleast-squares-calibration-line) — Metrology, chapter 2 - [Optical lever comparator magnification](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Aoptical-lever-comparator-numerical) — Metrology, chapter 7 - [Constructing and interpreting X-bar and R charts](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Ax-bar-r-chart-construction) — Metrology, chapter 15 ## Related in other subjects - [Slip gauges: wringing and building a size](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aslip-gauge-wringing-build-up) — Workshop Technology, chapter 4