Dimensioning Channel Sections - CAD Standard Question

[JoelTXCive]

I am designing a small work platform that will use Channel sections as beams. I'll have a series of channels running horizontally.

My question is: What is the CAD standard for dimensioning Channels on a framing plan?

Should I dimension to the center line of the flange? Centerline of the web? Or to the "exterior face" of the web? It seems that dimensioning to the face of the web would be easier for the contractor/fabricator to lay out?

If the 'back face' of the web, then what is the best way to describe that on the plans?

How about "Dimension lines shown are to exterior face of channel web?"

I've tried googling this and looking in my detailing books, but haven't found the answer.

Thank you.

 

[KootK]

1) if there's a standard, I don't know of it. Maybe one of our fabricator guys will.

2) exterior faces appeals to me strongly but I'm not entirely sure why. Maybe it cleanly defines edge of deck in some applications? Center of web would cleanly define the centres of double angle connections but, then, connections will likely be single angle. And in the age of computers/tesla, I'm not sure anybody cares.

3) Do your drawings rock a sexy steel framing legend? If so, it might be slick to throw a dimension leader on that and say that it's centreline for wide flanges and web face opposite flanges for channels. One and done.

 

[Agent666]

Round these parts it's typically to the back of the web, this is generally because this is the face being slapped against other members/cleats, and the face that flange bolt holes are setout from, etc. So it just makes the most sense if you're laying things out.

I usually put a little channel cross section on the plans, projected out from the end of the member to show the orientation of the flanges if its not clear from any details that might be referenced. Another way is to put the call-up on the web side on the plan.

 

[JoelTXCive]

Thank you all! I added a note to the sheet, and I also have a cross section showing dimension lines.

 

[canwesteng]

Back face of the web, and have a widget showing a piece of the channel in plan so it is obvious a) you dimensioned to the back face of the web b) which direction the flanges point. My company has software that does this but I've seen on old school hand drawings as well.