Interpretation of a symbol used to indicate a hole requirement in a technical illustration

For the symbol denoting a conducting connection to a chassis or frame on a printed-wiring board, IEEE Std 315 recommends referring to the source provided. Alternatively, when searching for the ohm or micro symbol, copying and pasting from Google search results is a quick solution. Word processors can also be used to autocomplete abbreviations like “kohm” into “kΩ”. Another option is to use AutoHotkey as a universal AutoCorrect and shortcut solution, where Hotstrings can be programmed for even faster typing.


Apologies for asking a straightforward question, but despite scouring multiple online resources, I have yet to find a concise response. Attached is a visual representation of my hole specification, which measures 3.4 with an added tolerance of 0.13.

What does the +0.13 mean?


Solution 1:

It is possible that this is referring to the acceptable dimensions of the circle’s diameter, which include both lower and higher tolerances.

The range of acceptable measurements is from 3.40mm as the minimum to 3.53mm as the maximum.

You require four through-holes in your specific scenario that fall within the specified tolerances of [3.40, 3.53].

Solution 2:


  • geometric dimensioning and tolerancing
  • Datum reference.

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