Lines & plumb bobs
Johnson Hexagonal steel plumb bob, 5 oz
The lightest bob here, and the only one sold for the job a surveyor actually keeps one for: centering a tripod.
Specifications
- Stated dimension or range
- 5 oz — the lightest bob on this shelf, where the heaviest is 21 oz. Light is the right choice for a tripod hook, where the bob hangs a few inches and settles in a moment; this shelf's introduction says a heavy bob steadies faster and swings less in a draft, and both of those matter on a long drop rather than a short one
- Functions
- Stated to be used with JOHNSON TRIPODS to center them while using optical and laser instruments. It is the only bob on this shelf sold for that job, and it is the job a surveyor keeps a bob for: an instrument reads angles from wherever its tripod actually stands, so a theodolite or a level over a station mark has to be positioned by dropping a point from its own center
- Material
- A hexagonal MACHINED steel body with a corrosion-resistant plated finish, stated. Machined rather than cold-drawn — which is the other bob on this shelf — means turned to shape, so the concentricity of the point to the body is a machining tolerance rather than a drawing one
- Body and fittings
- A hexagonal body stated to prevent it rolling off, and a removable cap stated to allow quick, easy and accurate Centered string installation. Centered is the operative word: a bob whose string is not on the axis hangs at a slight angle and its point lands beside the truth
- Supplied
- The bob. No line, no reel and no case — so the string is bought separately, and the cap is what makes that a specified job rather than a knot round a hook
- Also stated
- Named for foundation contractors, excavation contractors and surveyors, for lining up and transferring points. No settling time, no dimensions, no tip guard and no spare tip is published
- Amazon reference
- B00002N7U8
- EAN
- 0049448050000
What the maker puts in writing
- 5 oz · hexagonal machined steel body with a corrosion-resistant plated finish
- “The plumb bob tool has a hexagonal machined body that prevents it from rolling off”
- Removable cap allows quick, easy and accurate Centered string installation
- “You can also use it with Johnson tripods to level them into the center while using different optical and laser instruments”
- For foundation contractors, excavation contractors and surveyors; lining up and transferring points
No line. No settling time. No dimensions. No tip guard.
Five ounces, because the drop is short
And this listing names the job.
Centering a tripod means hanging a bob a few inches under the instrument head, over
a station mark. The line is short. The air under a tripod is still. It settles
almost at once whatever it weighs.
Carrying twenty-one ounces up a hill for that is weight for nothing.
For a long drop in a draft this shelf’s introduction is right and the heavy bob on
this shelf is the tool. For the job in this title, five ounces is correct.
The only bob here sold for a tripod
Which is what a surveyor actually keeps one for.
An instrument reads angles from wherever its tripod really stands. So a level or a
theodolite over a station mark has to be positioned by dropping a point from its
own center.
Every other bob on this shelf is sold for walls and door frames.
Centered string installation
The specification that matters most, and only two bobs here publish it.
A bob is a cone hanging from a point. If the string leaves the body off-axis, the
cone hangs tilted and the tip lands a few millimeters from where the line truly
falls.
Invisible, and wrong.
A removable cap that threads the cord through the Center is how that is
guaranteed. The rest describe a hook or a ring.
Machined, not drawn
The other hexagonal bob on this shelf is cold-drawn steel.
Machined means turned to shape, so the concentricity of the point to the body is a
machining tolerance rather than a drawing one.
Both are hexagonal, and both say why: a round bob rolls off a board.
And no line at all
Which is only a price question.
Nine dollars buys a bob. Fifteen on this shelf buys a bob with sixteen feet of
braided line, a board, two pencils and a sharpener.
What a bare bob gives you is the choice — and for tripod centering the right cord
is short, fine and non-stretch rather than a mason’s line, so a kit string would
be replaced anyway.
Availability
On sale at around 9 € on the American Amazon store at the time of checking.
Prices and availability are what Keepa reported on the date this page was updated; both move.
Prices quoted in this text were read on 8 October 2026. The live price is at the top of the page.
