TM 9-243
TYPES AND USES
PLUMB BOBS
A plumb bob is a precision instrument used to establish
a true vertical transfer and line-up reference point, and
to take readings or soundings in tanks and voids. Plumb
bobs are used by carpenters, surveyors and mainte-
nance technicians.
SURVEYOR'S POLISHED BRASS
The surveyor’s brass plumb bob may be either a spool
type (A) or an adjustable cap type (B). Both types have
replaceable steel points for increased accuracy. The
adjustable cap allows the operator to make minor cor-
rections to height and rotation to make sure the bob
hangs straight. The surveyor’s brass plumb bob comes
with a minimum of 7 feet of nylon, silk or linen cord. It
comes in 6, 8, 10, and 16 ounce sizes. The heavier
plumb bobs are better for use in windy areas.
SOLID STEEL
The solid steel plumb bob (A) may have a machined
integral head, body, and point. It may have just a remov-
able head (B), or a removable head and a replaceable
point (C). It may be round or hexagonal in shape and it
comes in 3, 8, and 12 ounce sizes. Cord for the solid
steel bobs must be obtained from a separate source.
This type plumb bob is used when extreme accuracy is
not required.
11-2
