Dual dimensioning units - surface roughness 3

[dgallup]

I've been asked to convert a couple of drawings to dual dimensioning units. This is easy to do with our CAD system for linear dimensions and geometric tolerances. Change on drawing configuration option and it's done. However, that has no effect on surface roughness symbols. I've never seen a dual dimensioned surface roughness symbol. Our symbols just have a text string for the roughness. Is it acceptable to do this:

50[1,2]

for the micro-inch[micron] values?

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[ctopher]

I have never seen surface texture with mixed units, they are usually either in µM or µIN.

Chris
SolidWorks 11
ctopher's home
SolidWorks Legion

 

[CheckerHater]

Roughness symbol can be troublesome as it is, without dual units.
Would you consider placing conversion table somewhere near titleblock?
Naturally, the note should be provided saying something like “SURFACE ROUGHNESS IN MICROINCHES, FOR MICROMETERS CONVERSION SEE TABLE 2”

 

[drawoh]

dgallup,

One of the many arguments against dual dimensions traditionally is that the conversions might be wrong. It sounds like this is still true.

--
JHG

 

[dgallup]

Believe me, I'm as anti dual dimensions as anyone, but when it has to be done it has to be done. The CAD system automatically takes care of most of it very well. It is just these surface finish tolerances that remain. ISO 1302-1978 (obsolete) recommends using roughness grade numbers to avoid misinterpretation of numerical values but since no one here is familiar with their use that would only add confusion in my opinion. I think I will add a table to each drawing, there are only 2 or 3 values on each drawing.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[CheckerHater]

Here is another interesting idea: To think of it, even obsolete symbology may be used, if you clearly explain what you are trying to achieve. Please check the following link:

http://content2.smcetech.com/pdf/Supplier_QA_Manual_Rev_13.pdf

This is remarkable document, created to ”level the field” for the suppliers, and make sure all of them will interpret company drawings in the same way.
The surface roughness chapter starts on the bottom of Page 18.
I am not saying this is the only way to do it, just an example.

 

[dgallup]

We have a similar document that explicitly states every drawing standard we use and any special symbols, etc. It does not say anything about units as we have drawings in both inch and metric. I'm not about to start using obsolete symbols!

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[pmarc]

I've been asked to convert a couple of drawings to dual dimensioning units. This is easy to do with our CAD system for linear dimensions and geometric tolerances. Change on drawing configuration option and it's done. However, that has no effect on surface roughness symbols. I've never seen a dual dimensioned surface roughness symbol. Our symbols just have a text string for the roughness. Is it acceptable to do this:
50[1,2]
for the micro-inch[micron] values?

I have been working with drawings using such convention. As long as there is a clear explanation on the drawing area or in a document referenced on the drawing as to what is what, I see no issues with that.

Correct conversion of dual dimensions is a different story.

 

[TheTick]

Two things I would not do:
1. Dual dimensions on surface roughness
2. Use vendors incapable of unit conversion