Understanding Jenny Spanners and Their Names

Jenny spanners, also known as odd-leg calipers or sometimes hermaphrodite calipers, are essential layout and measurement tools used in metalworking and engineering workshops. They are primarily used for marking lines parallel to an edge or finding the center of round stock.

Analyzing the Options

Let's look at the given options to find the correct alternative name for Jenny spanners:

• Outside caliper
• Joint spanner
• Inside caliper
• Odd-leg caliper

Explanation of the Correct Answer

A Jenny spanner has two legs, but they are different. One leg is a caliper leg with a pointed tip, and the other leg is a divider leg that is bent outwards near the point. This unique configuration is why it is often referred to by names that describe its appearance or function. The term "odd-leg" directly describes the fact that its two legs are different in shape and purpose.

Another less common name sometimes used for Jenny spanners is "hermaphrodite caliper" because it combines features of both inside and outside calipers or dividers. However, among the given options, "Odd-leg caliper" is the most widely recognized alternative name.

Let's examine why the other options are incorrect:

• Outside caliper: Used to measure the external size of an object. It has two curved legs that point inwards.
• Joint spanner: This term does not refer to a type of caliper or measuring tool. It might refer to a type of wrench used for tightening joints.
• Inside caliper: Used to measure the internal size of an opening or groove. It has two legs that curve outwards.

Based on the structure and function of a Jenny spanner, "Odd-leg caliper" accurately describes it and is a common alternative name.

Revision Table: Types of Calipers

Additional Information on Layout Tools

Layout tools like Jenny spanners are crucial before machining or shaping material. They help in accurately marking where cuts or holes should be made. Other common layout tools include:

• Surface Plate: A flat, rigid surface used as a reference plane.
• Surface Gauge: Used on a surface plate to scribe lines parallel to the surface plate or to check heights.
• Scribers: Hardened steel points used for scratching lines on metal surfaces.
• Punches (Center Punch, Prick Punch): Used to make indentations for drilling or marking.
• Rules and Squares: For measuring lengths and checking squareness.

Understanding the specific function and common names of each tool, like the Jenny spanner or Odd-leg caliper, is important for accurate work in manufacturing and fabrication.