Question About Symbols

[tomw]

Dear All,

I am attempting to build a model beam engine originally designed by Elmer Verburg. I downloaded the plan from John Tomlinson's site. I have made OK progress, but I am confused by some of the call-outs.

In particular, I don't know what the circled letters mean. For example, in the image below are circled C, S and P (outlined in red). On other parts of the plan you will also find a B.



Any help will be much appreciated. If this questions belongs elsewhere please let me know.

Cheers,

Tom

 

[Badspellar]

On the site you got the plans from is an appendix that explains everything. its after plan 52.

 

[Wreck™Wreck]

I suspect that the indicated symbols have been unused for 50 or more years and have been replaced by ANSI and ISO symbols. However a symbol inside a circle denotes round work,
Brings back memories however, the circled P on its back is perplexing in every way.

Does it mean perpendicular to another datum?
In the ISO Standards:
The symbol for two plane surfaces with a required parallel relationship is // with a tolerance band.http://www.gdandtbasics.com/wp-content/uploads/2014/12/Parallelism-Drawing-Callout.jpg

The symbol for concentricity for round parts with one or more concentric diameters is a circle within a circle with a tolerance band. http://www.emachineshop.com/machine-shop/assets/images/GDT/Concentricity.jpg

The ISO did a nice job of making the symbols easy to visually grasp the intent of if not the actual meaning.

I will have to look into the inclined P symbol as it would make an interesting avatar on a machinists forum

 

[4GSR]

Here it is on the first page of his appendix.

http://www.john-tom.com/ElmersEngines/ShopWisdomRevNov07.pdf

Definitely not supported by ANSI or ISO.

 

[loose1]

So is that something the drafter came up with or old methods?
Matt

 

[4GSR]

So is that something the drafter came up with or old methods?
Matt

It's probably something the drafter came up with. I recall doing the same thing on drawings way back before the days of cad and ISO standards. Even today, if a company wanted to do this for inhouse use or even for a contractor to use, there is no law or rules that say you can't do it. I don't think very highly about ISO. Especially when they try to dictate that it's their way or bust.