---
title: "End bar and universal measuring machines"
subject: "Metrology"
chapter: 14
key: "semester_3/metrology:end-bar-and-universal-measuring-machines"
source: https://www.bctengineer.com/q/semester_3/metrology/end-bar-and-universal-measuring-machines
site: BCT Engineering
---

# End bar and universal measuring machines

Metrology · Chapter 14: Measuring machines

- Asked in: year not given, 5 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/metrology/end-bar-and-universal-measuring-machines
- Whole chapter: https://www.bctengineer.com/md/semester_3/metrology/chapter-14

## Question

Describe the end bar measuring machine and the universal measuring machine, and state the main differences between them.

## Short answer

The end bar machine compares an unknown end standard with a master between fixed and movable anvils, reading the difference. The universal measuring machine measures lengths and features to 0.1 µm using a traversing head and a precision scale with attachments. UMM is general-purpose; the end bar machine is specifically for calibrating end bars and gap gauges.

## Answer

#### End bar measuring machine
It is a bench instrument for the calibration of end standards such as end bars, long gauge blocks and gap gauges up to 1 or 2 m. The unknown bar is placed between two anvils on a rigid bed. One anvil is fixed and the other is a movable anvil on a slide. A dial gauge or a micrometer head is used to measure the movement. The unknown bar is compared with a master of near size; the difference in the readings gives the deviation. Temperature of the work and master must be equal, and the measuring pressure is kept constant by a weight or a spring.

#### Universal measuring machine (UMM)
It is a bench instrument that measures the length of external and internal features directly, with a very high accuracy (down to 0.1 $\mu$m) and is more flexible than the micrometer. It has a rigid base with a measuring head and a tailstock. A measuring slide carries the head that moves along the table and the distance is measured with a precision scale or a line scale viewed through a microscope, or an optical/laser scale. The workpiece is held on a table between the two measuring contacts. A wide range of attachments is available: for internal diameters, thread pitch, gears, and so on. Measurement is done by comparison of the readings, with a set measuring force.

| | End bar machine | Universal measuring machine |
|---|---|---|
| Purpose | Calibration of end bars and gauges | General precision measurement of length, diameter, and many features |
| Range | Long (up to 2 m) | Moderate (commonly 100 to 1000 mm) |
| Axes | One (linear) | One main axis with attachments, sometimes more |
| Use | Standards room | Inspection room and tool room |
| Accuracy | Very high | High, to a micrometre or better |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the end bar measuring machine used for?
   A. Calibration of end standards (end bars, long gauge blocks) by comparison with a master of near size
   B. General precision measurement of many features with attachments
   C. Measuring surface roughness
   D. Measuring thread angles
   Answer: A. The unknown bar sits between a fixed and a movable anvil, and the difference from a master is read on a dial or micrometer. (Key point: End bar machine)

2. What makes the universal measuring machine more flexible?
   A. It works only on end bars up to 2 m
   B. A wide range of attachments for internal diameters, threads, gears etc.
   C. It has two fixed anvils
   D. It does not need a scale
   Answer: B. A UMM measures external and internal features directly with a precision scale and attachments. (Key point: UMM)

3. Which is a correct difference?
   A. UMM calibrates standards; end bar machine is used in the tool room
   B. End bar machine is multi-axis; UMM is single-axis only
   C. End bar machine has longer range (up to 2 m); UMM is for general measurement (commonly 100 to 1000 mm)
   D. UMM has the longer range of the two
   Answer: C. End bar machine: calibration of standards, long range, standards room. UMM: general inspection, moderate range. (Key point: Difference)

## Related in Metrology

- [Coordinate measuring machine and probes](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Acoordinate-measuring-machine-cmm) — Metrology, chapter 14

## Related in other subjects

- [How a universal Turing machine works](https://www.bctengineer.com/question.md?key=semester_3%2Ftheory_of_computation%3Auniversal-tm-example) — Theory of Computation, chapter 5
- [Machine learning; Boltzmann machines](https://www.bctengineer.com/question.md?key=semester_6%2Fartificial_intelligence%3Aml-boltzmann-machine) — Artificial Intelligence, chapter 6
- [Universal motor operation and applications](https://www.bctengineer.com/question.md?key=semester_4%2Felectrical_machines%3Auniversal-motor-operation-applications) — Electrical Machines, chapter 7, asked 3×
- [Universal motor and why so called](https://www.bctengineer.com/question.md?key=semester_4%2Felectrical_machine%3Auniversal-motor-construction-operation) — Electrical Machine, chapter 7