Basic Tool Mason Plum Bob
Zero Error Tool
It is truth that books were written from experiential but no one can do any thing by book, because fun is knowledge based and shifted from a practical person to others followers.
About 25 years ago a mason question me that what is man made thing which has no error, I went to think about man made machines daily used equipment, tools etc and guessed many things, he reject all my pointed tools, then I tired and let him to tell me, he did not replied only show his hand where plum bob was hanging & moving due to his hand motion I asked this one he smile and tell me from the time of its invention till to date no error/fault traced/calculated in it. So we proudly say a great tool was created by a great person that has no error was invented only for us I mean surveyors.
I thank full for this great invention of that whom I do not know.
Plum bob is metal made tool probably it made of mild steel, cast iron, brass etc here in Pakistan mild steel/cast iron plum bob used by masons, shuttering carpenters, steel fabricators plumbers and brass made used by practical engineers/professional surveyors.
It is a simple tool having 3 parts 1, Lotto 2, Thread/Silk wire3, Kanda as shown in the sketch.
1,Lotto
About 120 gram mild steel lotto made on lath machine mostly having No-7 used in general professionals here in Pakistan having conical pointer below and two 3/32”.hole in its neck one across neck horizontally and one from top to some below horizontal hole (in past a brass neck with thread and hole was separate)
2, Holding wire
Holding wire mostly 15 feet long maximum 1/16” thick made of thread or pure silk used.
3, Kanda
Third part of this historical tool is kanda it also made of mild steel 5/16” round bar its length is equal to outer dia of lotto usually 1 ½”. A hole 3/32” made 1/16” a side from its center length wise.
Uses of plum bob
I do not know its history but here in indo-pak subcontinent many monuments constructed by Mughals Empire are still questing to the new world how we are still holding our position and having attraction who design us who construct us and who finish us what was their qualification from where they got a P.H.D,Masters,Bachular&Diplomas.
I have no answer if any body has answer please must inform to me for my knowledge.
I have a simple answer that they were devoted professionals.
They used a basic tool who has his advantage from centuries to this global connected modern world.
Every one do not know the base of plum bob but when they need truly reference or calibration only basic tool will be standing alone with its centuries advantage. for a reference check the box of latest survey instrument. Many surveyors commented that manufacturer put it to complete/increase the weight of instrument box because they are technically innocent.
As per history tell to me by a kasuri mason North meridian/line were forwarded by two plum bob hanging on two big wooden (ghori) stools such used in scaffolding in building construction and a professional range them with eye sight and forward/establish line. Also this method applied to make truly vertical with single plum bob & stool.
In above two methods professional sat about a distance from stool and range.
Now we use it only for to put a structure member verticality. Such as wall plaster,pipe,columns,etc and to shift the points from ground floor to first & all above floors. when we its change its direction 1/16” apart kanda hole of wire is to ensure -1/16”& +1/16” vertical. Everyone have not a concept about it because it is fun not a game. here in Pakistan mostly named professionals having foreign degrees speaking English wearing pent shirts but never touch the basic or modern surveying instrument in the field they do not know the base of survey but called foreign qualified.
Calibration
No need to calibration of it only check the size of kanda is equal to dia of lotto and thread/silk wire thickness should not less than hole of wire in the neck of plum bob.
Note:- District Kasur is in Punjab Pakistan most of historical buildings were constructed by kasuri masons or their followers.
Sorry to those who has objection on my writing & language
It is my first topic hope you all will like and soon I will try to write on other basic tools
Thanking you all
M akram shahid
Thoughts