Controlling finish on drawings.

[steveedmonds]

Hi.
We are applying GD&T to our drawings to place controls on machining of our products so that the expectations from any subcontractor meet those unwritten expectations of our own shop and selected managed contractors.
This has been a learning curve and surprisingly the subcontractors have not questioned the change to GD&T on the drawings.
Where we struggle at present is in how to apply control of the visual appearance on the drawings. The products are bright nickel plated or electro-polished stainless steel and visual appearance is significant. The attachment link (700kB jpg)shows some images of finishes, acceptable and unacceptable. The unacceptable finishes in the images in fact have a smaller Ra roughness but it is the non-uniform pattern that is not acceptable. We don't wish to introduce additional cost of specifying grinding or polishing if it is unnecessary.
Can anyone suggest a means of applying this information to a drawing, would it require reference to say this link or another means of specification such as a standard.

Thanks,
steve

 

[handleman]

I believe there are letters to denote the "lay" of the machining lines on the surface. Here's a really horrible link:

http://books.google.com/books?id=my...&hl=en&sa=X&oi=book_result&resnum=4&ct=result

Sorry, can't find better at the moment.

-handleman, CSWP (The new, easy test)

 

[ctopher]

There is a difference between 'roughness' and 'finish'.
Finish would be, for example, 'anodize'.
Roughness would be the surface itself.

A lot of people/companies call it 'surface finish'.

http://www.jjjtrain.com/vms/eng_surface/eng_surface_02.html

http://www.engineersedge.com/surface_finish.htm

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

 

[drawoh]

handleman,

Finish specification lay lines are described in the ever popular Machinery's Handbook.

JHG

 

[steveedmonds]

Thanks. I suppose then I am trying to control lay lines using standard symbols.
At what point would the circular lay lines of a face mill become perpendicular as there does not seem to be a symbol for this lay.
When I can accept 3 lay line styles, would I put all 3 in the finish symbol check mark (perpendicular, circular and longitudinal)

steve

 

[ctopher]

Add the roughness symbol/info to the drawing, let the machine shop do the rest. They will have to meet the spec.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion