This type of thread is given on the screw of bench vice.

Explanation:

Engineer’s vice/Bench vice:

• Vices are used for holding the workpieces.
• They are available in different types.
• The vice used for bench work is the bench vice or called Engineer’s vice.
• A bench vice is made of cast iron or cast steel and it is used to hold the work for filing, sawing, threading, and other hand operations.
• A square thread is given on the screw of the bench vice.
• The size of the vice is stated by the width of the jaws. eg. 150mm parallel jaw bench vice.
• Vices are mounted rigidly on a workbench with the fixed jaw in line with the bench edge to permit a long work to be clamped in a vertical position.
• For the convenience of working, the vice should be held at a correct height i.e. when the fist is pressed against the chin the elbow should touch the top of the vice.
• For further height adjustments, wooden platforms can be used.

Square thread: 

• In this thread, the flanks are perpendicular to the axis of the thread. This is used for transmitting motion or power. E.g. Fly presses, Screw jack, vice handles, cross-slide, and compound slide, etc.