I think "certain technical fields" refer to those that use pen plotters to print out (plot) drawings...wandererfan wrote: ↑Thu Apr 21, 2022 2:49 pm I can duplicate the ASME gap logic for ISO, but what does the "certain technical fields" mean? Does the gap have to be specified for some dimensions, but not others? Can we just always leave a gap?
A pen plotter is like 3D printer with only a restricted z axis; it can only lift and lower a pen.
On line crossings or at the start of a line (e.g. extension line), when the plotter paused too long after lowering the pen, the amount of ink flowing from the pen could have been too much for the paper to keep it in place until it had dried. It was likely to get dots at such points.
To avoid dots where they don't belong, gaps work fine.
But who really remembers the times of pen plotters? Since ink-jet and laser plotters took over, there's no technical need for gaps on drawings anymore. It seems like a tradition some older people don't want to give up. Gaps found their way into the standards and as they don't do harm to anyone, there's no pressure to remove them.
I only use gaps, when someone who pays for my work insists on having them. To me they are useless.
But in the end it is fine that we are now able to choose to use gaps or not.