What dose the symbol "~" denotes in the drawing which is located at the top left corenr of 1

[Rhyder88]

Hello
I observed some drawings having the symbol " ~ " without quotes , size is little larger , at the top left corner of the drawing sheet.

What does it denotes?

 

[CheckerHater]

Old German symbols for surface texture.
“Tilde” – no material removal
1 triangle – Ra 12.5
2 triangles - Ra 6.3 to 1.6
3 triangles - Ra 0.8 to 0.2
4 triangles - Ra 0.1 to 0.05

 

[pmarc]

Yep, this is it.
The picture attached by CH as well as some other information can be found here:

http://www.mcadcentral.com/proe/forum/forum_posts.asp?TID=26824&KW=german+grind+symbol

 

[CheckerHater]

Google-searched for "tilde", pmarc?

 

[ctopher]

Showing it before a dimension could also mean "approximately" (which shouldn't be on a drawing in this context anyway).

Chris
SolidWorks 11
ctopher's home
SolidWorks Legion

 

[pmarc]

CH,
Way more sophisticated option: "tilde + drawing"

 

[CheckerHater]

I looked for “tilde on drawings”, or something like that.

Just in case, there is another place here with little more details: Link

 

[juergenwt]

Tilde = swung dash ~

 

[CheckerHater]

Long time ago in some REALLY old book it actually looked like “infinity” symbol ∞
Does anyone out there remember that?

Also, it looks like nowadays in hands of “creative drafters” the symbol degenerated into something that was discussed in this thread:

http://www.eng-tips.com/viewthread.cfm?qid=276296

 

[Rhyder88]

Glad to see these much interesting replies, my dear friends. With help of your replies, i got an idea for the symbol ~ .

When i googled now i got one reference....20 th page of this PDF has some clear cut definition.

http://files.smcetech.com/pdf/corporate/QA_Manual_Supplier.pdf

 

[Rhyder88]

oh, sorry , i forgot to paste the definition. Here it is:

C. Surface Finish Call-outs:
The general surface finish specification used on the drawing is shown in the top right hand
corner of the drawing, to the left of the revision block. The number above the triangles
indicates the maximum roughness value (Ra or Rz) in microns (um) for the surface
designated by the triangle(s). The notation is interpreted as follows:

~ The tilde surface finish designator indicates that the surface is not
machined and the surface finish is controlled by the raw material surface
finish tolerance.

Two horizontal lines drawn through the surface finish designator
indicates the surface finish tolerance is not used anywhere on the
drawing.

Parenthesis around a surface finish designator indicates that the
designator is called out on the drawing. It is attached to either the
dimension line or the object line of the surface. More than one designator
can be called out like this in a drawing.

A surface finish designator without any of the above notations or one
that is that is underlined is used for all machined surfaces that are not
called out by a designator. Only one designator is called out like this in a
drawing