Lengthening bar

A lengthening bar is a drawing instrument used to draw larger circles than a standard compass can typically accommodate.

It is typically included as part of a standard engineering drawing instrument box. According to the sources, its key features and functions include:

• Attachment: It is designed to be fitted directly to a large compass.
• Assembly: To use it, a pencil point or pen point is inserted into the end of the lengthening bar.
• Purpose: It effectively extends the reach of the compass arm, allowing the user to draw arcs and circles with a significantly larger radius.

To draw larger circles, it is fitted to the compass. The pencil point or pen point is inserted to its end.