Understanding Indirect Measuring Instruments

Indirect measuring instruments are tools used to measure dimensions that cannot be directly measured using a standard scale like a steel rule. They often work by comparing the workpiece dimension to a known standard or by transferring a dimension. These instruments are crucial for tasks requiring precision and the transfer of measurements between different measuring devices or from a reference standard to a workpiece.

Analyzing Measurement Transfer Tools

The question asks for an instrument specifically used for transferring measurements between a steel rule and a job (workpiece). Let's look at the options:

• Compass: While a compass can be used to scribe circles or transfer distances, its primary function isn't the precise transfer of linear measurements between a rule and a workpiece in the context of machining or fitting.
• French curve: A French curve is a tool used in drafting and design to draw smooth, irregular curves. It is not a measuring instrument.
• Protractor: A protractor is used to measure or draw angles. It does not facilitate the transfer of linear measurements from a steel rule.
• Caliper: Calipers, such as outside calipers, inside calipers, or vernier calipers, are designed to measure distances or dimensions. They are often used in conjunction with a steel rule. For instance, you might set the jaws of an outside caliper precisely to a measurement indicated on a steel rule, and then use those set jaws to check or transfer that measurement to a workpiece. This makes the caliper an excellent tool for indirect measurement and transferring measurements.

Identifying the Correct Instrument

Based on the functions described, the caliper is the tool specifically designed for the purpose of transferring linear measurements from a reference, like a steel rule, to a workpiece, or vice versa. It acts as a bridge between the direct reading of the rule and the dimension needed on the part.