Plumb bob

[mklotz]

Every well-appointed toolbox, be it woodworker or metalworker, needs a good plumb bob. As metalworkers it would be a criminal offense to not make our own.

Here's one I made...

The body is solid brass although you could hollow it out and fill it with mercury or bird shot to get a bit of added weight. For durability, the point is made of steel and can be unscrewed with the aid of the wrench flats if the point needs sharpening.

The line is terminated with a small steel ball that nestles into a conical hole in the spherical cap when the cap is screwed onto the body. With this arrangement, the bob is free to align itself axially with the suspension line.

Overall length is about ten cmm and the weight is about 225 gm.

Novices who are looking for a starter project and/or a gift for another tool user might consider a plumb bob. It's undemanding dimensionally and offers lots of opportunities for creative variation.

 

[cidrontmg]

The body is solid brass although you could hollow it out and fill it with mercury or bird shot to get a bit of added weight.

Hm. I´m not sure that would be a good idea. As an ex-dentist, I have great respect for mercury, and its amalgams, and vapor. If there´s the slightest change that the ball which screws on the bob, where the cord is attached, is not air tight, I wouldn´t do it. And there seems to be an open passage to outside (the hole for the cord). That would mean it is all the time leaking mercury vapor in the air... And if you would shake it, upside down...
Use bird shot, or cast it full of lead, if it´s not heavy enough as it is, solid. Do NOT fill it with mercury.

 

[Stan]

I guess all instrument techs who worked with pneumatics must have died a horrible death from mercury poisoning. Open top mercury manometers sat on every bench and and at least once a day mercury was blown out the top from overpressure. We just cleaned it up as best we could and put it in the waste mercury container.

Aside from that, filling your teeth with it may not be the best idea and feeding mercury laden fish to small children is also a bad idea.

 

[Maryak]

Fang Farriers and Mercury reminds me of a time when I decided to calibrate one of our Kentometers. Turned my wedding ring silver and our tame fleet dentist polished the mercury out and restored its' pristine golden shine. It's just a shame that he couldn't do the same for the owner or his teeth.

Best Regards
Bob

 

[tel]

Hmmm .... mercury was a highly prized item when we were kids - used to fish around under the doors of those gas box thingies on the streets with a bit of wire, hoping to roll a bit out.

That said, it is pretty easy to make a plugged chamber in a plumb bob to contain said mercury - it does not want to be loose to the detachable point or string hole.

 

[cidrontmg]

I guess all instrument techs who worked with pneumatics must have died a horrible death from mercury poisoning. Open top mercury manometers sat on every bench and and at least once a day mercury was blown out the top from overpressure. We just cleaned it up as best we could and put it in the waste mercury container.

Aside from that, filling your teeth with it may not be the best idea and feeding mercury laden fish to small children is also a bad idea.

Well, AFAIK, dying a horrible (or even a pleasant..) death from mercury poisoning has not happened to anyone. You would get awfully sick (and seek help) far before that could happen. In fact, you can swallow mercury, you can inject it IV or IM (IV=intra-venous, IM=intra-muscular), and it won´t kill you. You can eat some mercury compounds without any instant or long-term harm. As with all metal poisonings, the effects of metallic mercury are cumulative, they happen only with prolonged exposure (mercury compounds are another thing, there are some quite toxic and fast-acting Hg compounds).
On a lighter (?) note, a character in Lewis Carroll´s "Alice in Wonderland" is Mad Hatter. At the time of its writing (and a long time before also), mad hatters were quite a common feature in any big European city. Hatters used mercury compounds when making and forming the felt for hats, and their effects were readily recognizable...
Another funny(?) mercury property. Aluminium will amalgamate with mercury if there´s even a slight scratch in the Al oxide layer which protects it. Al amalgam readily reacts with water (moisture in the air), creating aluminium hydroxide (Al(OH)3) and hydrogen gas (H2). The process will continue for quite some time, the aluminium being "eaten" away, far more than you would expect. It is converted to long, fluffy strands of (Al(OH)3). I´ve done them myself, they´re weird looking, long white strands, and very fragile. Sneeze, and they´re gone. Large amounts of mercury are not allowed aboard aircraft under most circumstances because of the risk of it forming amalgam with exposed aluminium parts in the aircraft. In the Second World War, mercury may have been used to sabotage aircraft.
I still think it´s unwise to create a source of mercury vapor in the shop... ;D

 

[kjk]

When I was in grad school, one of my friends fell horribly ill. He was hospitalized and diagnosed eventually with mercury poisoning. Because he was a grad student in Chemistry, a search was conducted in his lab for the source of the poisoning. It turned out that he was in the habit of warming up his lunch in the glassware drying cabinet, and someone, at some point, had spilled some mercury in the cabinet producing a very high concentration of mercury vapor.

 

[shred]

Vapor very bad.. metal, not so bad. My dad tells a story (I don't know where he got it) of renovating an old chemistry lab at some aged and hallowed English University.. said they pulled up the floorboards and found large pools of mercury underneath from several hundred years worth of broken thermometers, manometers and such experiments. Nowdays we call out the haz-mat team for every cracked thermostat instead of letting it slip through the gaps in the floor.

Heavy metals poisoning is nothing to sneeze at though-- do be very careful with any of the vapors-- lead, mercury, cadmium, etc.

 

[modeng2000]

I have a mercury barometer hanging on the wall of the study.
Does this present a hazard?

John

 

[deverett]

Many moons ago, I took a ship to scrap in China. We stopped off in Singapore on the way and flogged off as much scrap non-ferrous metal that we could shift and made a bit of beer money for ourselves. We also had quite a few kilos of mercury from the old King gauges (for finding the quantity of fluid in tanks) and tried to sell that at the same time, but the scrappie wouldn't touch it. Pity, because it was worth about $900/flask. Musta been the open jam jars we put it in!

Dave
The Emerald Isle

 

[cidrontmg]

I have a mercury barometer hanging on the wall of the study.
Does this present a hazard?

John

If it´s open ended, as they usually are, and if you (or anyone else) spend a lot of time in the study, I would rather not have it there. A lot depends on how warm the wall usually is. Also it depends on the ventilation of the study. At least don´t mount it on the mantelpiece, or straight above a heating radiator. I guess it´s more in the way of decoration, but if you really want daily barometric data, consider changing it for an aneroid.

 

[Brian Rupnow]

Mercury is nasty stuff. Have you ever heard the expression "Mad as a hatter"---Thats a saying based in truth---Hat makers in Merry England used mercury as part of the process for making felted hats. After enough years of exposure to the mercury and the fumes from it, they were literally insane.

 

[wheeltapper]

Is this not getting a bit out of hand, just how heavy does a plumb bob need to be for **** sake.

Roy

 

[TREBOR]

What about using plutonium , that heavy :

Fred

 

[cidrontmg]

Sorry Marv, this has really gone off topic, and I started it. In my "defense", I will only plead that whenever I hear/read the word mercury (not meaning the planet, or car, but the metal) I get double attentive, it´s like a siren going off, and little men waving red flags all over. I´ve seen and heard about some of my ex-colleagues developing various degrees of Hg poisoning, and I think I also suffered some ill effects of it. I guess I still am mad as a hatter when it comes to mercury. After >20 years since I stopped handling it.
I didn´t mean to turn this thread into a debate about the dangers of mercury, just to point out a possible design flaw. Sorry about the mess.

wheeltapper : A plumb bob needs to be so heavy that it won´t get pushed away by the wind grabbing the line where it hangs on. No more, no less.
TREBOR: A tungsten bob would be the ultimate.

 

[Brian Rupnow]

Now if we could just scoop up a wee bit o' matter from the center of a black hole----

 

[rcmadness]

I am with you Brian, a wee bit of the black stuff would sure keep it from blowing in the wind. Now as far as the string goes, what would you make that out of with a plumb bob that weighted as much as a planet. ;D

The mad hatters of merry old england used leather bags to form the hats in molds. When the hat was through forming they stuck a tube into the neck of the leather bag and sucked on it to start the mercury flowing into a bucket setting on the floor. They completed this process many times a day. Not only did they get the vapors they believe they ingested quite a bit also.

Old Gunsmiths also use mercury to melt the lead out of badly leaded gun barrels.

None the less don't breath the fumes and if you have some don't keep it in glass containers and don't tell your "green" neighbors you have the stuff.

 

[kwoodhands]

Is this not getting a bit out of hand, just how heavy does a plumb bob need to be for **** sake.

Roy

Roy ,I was given a mercury plumb bob for Christmas many years ago. The plumb bob was not much, if any heavier than a brass or steel one. The advantage to the mercury bob was it comes to a stop quickly. It sort of shakes a bit ,then comes to a sudden stop.Some thief stole it from a transit I had set up while I was away from the instrument.The mercury bob was a big improvement to standard plumb bobs. They must have been expensive as I have only seen them twice since I had mine in 1967.

mike

 

[kcmillin]

Can the average person even purchase mercury? It seems like it should be a controlled substance.

Kel

 

[1Kenny]

Mercury is not illegal. Yes, the average person can buy it. If a person is nervous about using it, then don't use it. Please don't try to get it banned for those of us that do use it and are carefull with it.

Kenny

Edit: Here is one place that sells it.
http://secure.sciencecompany.com/Mercury-Metal-quicksilver-3X-Distilled-250g-P16388C670.aspx