Plumb Bobs

Plumb Bobs

A plumb bob is essentially a weight with a pointed tip on one end, and the other end is suspended from a cord. This tool is used as a plumb line or a vertical orientation line. Plumb bobs are also used to establish the lowest level in space through the use of gravity.

There exist only a few different forms of the tool, all developed from the basic model of a weight suspended on a string. However, these tools can be broadly categorized as

• Traditional plumb bob: These are the original form of the item, made up of a long cord tied to a pointed weight for accurate marking.
• Flat plumb bob: This type has a flat face that enables it to hang close to the vertical surface, with a central perpendicular slot for precision marking.

It is important to note that all of them are symmetrical in shape, but they can be categorized into

• Naturalistic shapes: They resemble fruits, vegetables, and nuts and are differentiated by the names pear, ovate or egg, teardrop, turnip, and apple.
• Geometric shapes: These types are modified and used as the sphere, cylinder, cone, or a combination of various shapes such as hexagonal cylinder, pencil point, ice cream cone, and tapered cylinder.
• Formal shapes: These include the barrel, doorknocker, and chalice. The designs have a different aesthetic purpose than the other types.

A plumb bob should be as heavy and as compact as possible. These tools are used when they are at rest, and heavy materials tend to help with speed, accuracy, and ease of taking readings. The tools can be:

• Crafted from dense stones
• Cast from lead
• Made from alloys of tin and copper

Given that the tool must be shaped into a symmetrical form and a cord must be attached to the axis of symmetry, the choice of base material depends on the availability of technology to craft the material.

• Screw caps: Allows the cord to project directly from the epicenter of the mass, facilitating greater balance and precision.
• Reels: These are meant to help unwind the cord.
• Replaceable tips: Most tools come with detachable parts. The screw cap and tip both unscrew from the body of the instrument. These parts are cast from metals such as steel.