- Practice · 5 marks
End bar and universal measuring machines
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.
Describe the end bar measuring machine and the universal measuring machine, and state the main differences between them.
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 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 |
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Coordinate measuring machine and probes · Metrology, chapter 14
- How a universal Turing machine works · Theory of Computation, chapter 5
- Machine learning; Boltzmann machines · Artificial Intelligence, chapter 6
- Universal motor operation and applications · Electrical Machines, chapter 7 · asked 3×
- Universal motor and why so called · Electrical Machine, chapter 7