Rant: ANSI vs ISO

Most of my career has been spent denying that 2D exists. I (half) jokingly tell customers that I charge triple rate for 2D drawings. Typically, I wind up doing some simple drawings when I hand off part data to a molder. But only big overall dimensions, some special finishes, and tolerances that are out of the ordinary.

Still, the fact that I avoid drawings as much as possible doesn’t mean I don’t know anything. One of my biggest pet peeves about users and CAD developers is that they don’t know the difference between ANSI and ISO. It gets even worse when you start mixing first and third angle projections. I think I many have complained recently that some training I attended set up a drawing with an ISO template, and proceeded to use first angle projections as if there was nothing wrong. That’s like sins-a-CAD-guy-should-never-commit-101. Sure, the guy should have known better, but the CAD developer could also do better.

I know two CAD software products that if you aren’t careful, you can install ISO as the default here in the US. When software is installed, there is all sorts of information available to the the installing application. One of those is what country the software is being installed in. If CAD software is being installed in the US, there’s a pretty good chance that ANSI will be a better choice than ISO. This is one of those things that’s basic drafting class information, and that must drive CAD Admins crazy.

I was just re-installing Solid Edge tonight, and right up front, it does have it there, is the choice for ISO or ANSI, but the default is ISO. This should be easy to fix. I have run into companies in the US that do use ISO, or an ISO-ish standard. I have also run into one company that uses first angle projection because they work primarily with companies from European countries who use that standard. I’ve never seen anyone implement ANSI or ISO 100% to the letter, but the difference between projection methods is subtle yet extremely important. Sending a wrong projection drawing is likely to cost you a lot of money.

What do you think CAD developers could do to help with standards compliance?


Updated: May 17, 2013 — 9:27 pm


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  1. There is another bit of a silliness that happens in the 2D side of things besides ANSI and ISO and it is fonts of all things. In SE the default SE font is not standard true type and when you export to DWG some of the text gets garbled. It falls into the category of silly things that happen that should not. Now you can go in there and change the default font and eliminate the problem but why the heck does the problem even exist???  ANSI should be default and fonts ought to be correct for DWG’s. Simple stuff that trips everyone up until you learn to be on guard against it.

    Hey Matt, is this the same guy that did not like the steering wheel?

  2. I’m always confused is it still ANSI or is it governed by ASME now, the US drafting standards?

    As for projection methods, as a European and as such a user of ISO, I  often curse against our own first-angle projection. It sometimes makes no sense that a projected view looking at the bottom of the part is of course, then, put on top of its parent view.

    Also what ticks me off is the different between ISO and AWS for welding symbols, because some things (like this side/other side welds) are completely opposite to each other!

    1. Yes, I believe it was a “merger” that happened between ASME and ASNI quite a few years back. ASME is now the controlling group.

      Weld symbols..that’s one that will really hose up a project!


  3. I would argue that projection methods are not subtle. Having views reversed on you is as far from subtle as I could imagine.  Having a comma for a decimal indicator would be subtle… :-)

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