enter image description here

I was looking through AMSE Y14-5 and noticed that they tend to use diameter symbols in their drawings, which is indicative of an ISO standard. enter image description here enter image description here

However, I always thought that ASME Y14-5, being American, would follow ANSI as opposed to ISO. Such as this random person online who mentioned that ASME follows ANSI : https://grabcad.com/questions/what-is-the-difference-between-ansi-and-iso-drafting-standard

Doing a quick search online I've gotten only more confused, and was wondering if someone could explain/help clarify this.

Edit: Even sites like this: https://www.cobanengineering.com/geometricdimensioningandtolerancing/TechnicalDrawingLines.asp

seem to say that diameter symbols, and calling out a radius as R0.250 is ANSI.

I am very lost :(

enter image description here


1 Answer 1


ASME follows the ANSI drafting standard.

Both ANSI and ISO have adopted many of the other standard as an alternative, so many companies have mixed and matched the drafting standards to create their own, oddball standard.

The basic, visual differences between the ANSI drafting standard and ISO drafting standard:

ANSI dimensions are read horizontally. ISO dimensions are parallel to the dimension line.

ANSI dimensions are centered on the dimension line. ISO dimension are placed above the dimension line.

ANSI tends to use abbreviations. ISO uses symbols. (example: RAD, DIAM, 3 PLACES versus R, Ø, 3X)

dimensions have a different syntax. ANSI: 1.000 DIAM 3 PLACES ISO: 3X Ø 1

I would suggest you google for them. Many are not free and you need to pay for them. Start by looking for a list of the standards, there are lots of them. https://www.asme.org/codes-standards https://www.iso.org/standards.html https://www.ansi.org/ These are the home pages, this should get you started/

  • $\begingroup$ Thanks for the reply! Do you know anywhere I can read up more on the ANSI, or ISO standards? Also, I wonder why the official ASME diagrams would show ISO symbols, and have that "mix" you mentioned. $\endgroup$ Commented Jul 16, 2021 at 2:55
  • 2
    $\begingroup$ If you want to know what the standards say, read the standards. (They are not free, because they are produced by teams of experienced people who have to be paid for doing a soul-destroying task like writing standards, instead of something else that pays well and is more interesting!) If you want to know what "some guys on the internet" think they say - well it should be obvious what to do! $\endgroup$
    – alephzero
    Commented Jul 16, 2021 at 3:15
  • $\begingroup$ More likely ANSI and ISO follow ASME as ASME was the first general standard. ISO is a relative newcomer, not to offend any national pride. $\endgroup$ Commented Jul 16, 2021 at 14:33
  • 1
    $\begingroup$ Just a note, I and many others serve or have served on these committees as volunteers, not paid members. Some may draw wages from there employer to do this but not all. Yes we have to pay for the standards we were not involved with drafting. $\endgroup$
    – Gil
    Commented Jul 16, 2021 at 16:34
  • $\begingroup$ I see, I didn't know what ASME was the first! Thanks for that information. $\endgroup$ Commented Jul 19, 2021 at 3:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.