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Four standards families a real engineering drawing carries at once: welding symbols under ISO 2553 or AWS A2.4, geometric tolerance characteristics under ISO 1101 or ASME Y14.5, surface texture under ISO 1302, and fluid power and process instrumentation under ISO 1219 and ISA 5.1. Where the ISO and American conventions produce a physically different part — the weld arrow-side rule above all — the members name the divergence rather than describing one system as the system. Two tolerance characteristics in the group were withdrawn from ASME Y14.5 in 2018 and remain current in ISO practice, which the records state with the year.
Which side of the reference line a weld symbol sits on.
A right triangle marking a weld in the corner of a joint.
Shapes naming how the joint edges are prepared.
A circle at the reference line's elbow, calling for a continuous weld.
A small flag saying the weld is made on site.
A line and letter saying what shape the finished weld must be.
Letters on a reference line calling for a named inspection method.
A tick with added bars and numbers specifying roughness.
A mark saying which way the machining marks must run.
A single straight line inside a tolerance frame.
A plain circle inside a tolerance frame.
A circle between two slanting lines in a tolerance frame.
A half-circle, open or closed, controlling a whole shape.
An angle sign in a frame, controlling orientation to a datum.
Two slanting parallel lines in a tolerance frame.
A crossed circle limiting where a feature may sit.
Two circles sharing a centre in a tolerance frame.
Three horizontal lines in a tolerance frame.
One or two slanting arrows controlling wobble about an axis.
A circled M allowing extra tolerance as a feature shrinks.
A dimension in a rectangle, exact by definition.
A downward arrow saying how deep a hole goes.
A capital S before the diameter sign.
A small square before a dimension, marking a square feature.
Two shallow triangles distinguishing a cone from a wedge.
Diagonal lines showing solid material a cut has passed through.
Continuous, dashed and chain lines each meaning something different.
Thin lines with arrows tying a note or a size to a feature.
A letter code and numbers naming a screw thread completely.
A crossed or straight pattern note specifying a gripping surface.
A scalloped outline around what has changed since the last issue.
Adjacent boxes whose arrows show each switched position.
A single box with an arrow and a spring, limiting pressure.
A circle with a solid triangle pointing out of it.
A rectangle with a piston and rod showing how it acts.
A rounded vessel storing energy under pressure.
Solid, dashed and dot-dashed lines for working, pilot and drain.
A circle with letters and a number tagging a process instrument.
Patterned lines distinguishing pneumatic, electric and software signals.
Two short lines across a pipe, measuring flow by pressure drop.
Line weight distinguishing main process flow from services.
A code in the tail of a welding symbol naming the process.
A divided circle naming a point, line or area of contact.
A circled P extending a tolerance zone beyond the part.
A circle or a double circle on a leader, extending a callout.
A circled F applying a tolerance to an unrestrained part.
A marked callout permitting statistical rather than worst-case control.