Allow Parameters to be included in Superscript and Subscript text syntax

[Bernie]

Add ability for use of parameters in the Superscript and Subscript text syntax @+<param_name>@# and @-<param_name>@#

This would be very useful for custom hole charts with hole callout notes when certain hole sizes have non-symmetric tolerances.

For example the tap drill for a #4 helical insert is a #31 drill, .120" diameter.  Allowed minor diameter per NASM spec (rounded to 3 place decimals) is .118"-.125".  So the preferred hole callout would be .120+.005/-.002.  This uses the standard tap drill and the tolerance range permitted per the NASM spec. When displaying this hole callout on a drawing or model annotation we would typically stack the tolerances (i.e. +.005 over the -.002) in super/subscript.  This is currently not possible when the hole sizes and tolerances are entered into the hole chart as parameters, since the Superscript and Subscript syntax above only allows plain text.

[BenLoosli]

Since you are dealing with a standard drill diameter and tolerance per a spec, leave the tolerance off the drawing and let manufacturing use their best practices to produce a hole within tolerance for a tapped hole. Inspecting a tapped hole between drilling and tapping operations is an expense that is hardly justified. Tolerance only helps when inspecting the hole.

[Bernie]

The example listed was just one scenario where use of a parameter in the super/subscript syntax would be advantageous .  I've seen inquiries from other users looking for this functionality for other purposes, but I didn't see an idea submitted yet to give it some visibility.  So regardless of this specific example, I believe this functionality in the super/subscript syntax would be helpful for some users.

Thanks for the suggestion regarding the specific example, it would indeed be easiest for us to only reference the hole spec on the drawing and let manufacturing do the rest.  Unfortunately I know from experience that this would often turn into manufacturing manually marking up the drawings with all the relevant hole and tapping info for use on the shop floor and inspection.  The "drill diameter" I was referring to is actually the minor diameter of the finished threaded hole that will be noted on the drawing.  We typically set the nominal minor diameter of the tapped hole to the closest standard drill size that is within the minor diameter's tolerance range, since that is the drill they will actually use.  The minor diameter of the finished threaded hole is inspected separately from the thread itself.  I believe they typically use a thread go/no-go plug gage on the thread and then a cylindrical go/no-go for the minor diameter. 

So in this case if we remove the tolerance from the minor diameter it would then default to the standard block tolerance, which may not be suitable.  If we remove the dimension altogether, or make it reference, then manufacturing will end up adding it back in manually from the spec.  So if we can drive the useful hole information from model/parameter based annotations by putting it into a hole chart once, it will end up saving time for people down the road and potentially preventing some errors along the way.

[BenLoosli]

Holes do not default to the standard  tolerance block. There is a separate spec for drilled hole diameters and their tolerances. Sheet metal with punched holes may be a different issue.

If you are doing your machining with CNC equipment, then your programmers should be using a standard tapped drill size. I have modified our company hole files so they use standard drill sizes, not the calculated  values that PTC supplies.

[Bernie]

These are tapped holes for NASM helical inserts and there is a specific spec controlling the minor diameter (and the rest of the prepared hole), and it is inspected.  We either put the thread and minor diameter w/ tolerance on the drawing (preferably model/parameter driven from our custom hole chart), or manufacturing puts it on the shop drawings manually to save the inspectors the time of pulling up the spec every time they need to check the hole.

Again this is just one example of the use of parameters in the Superscript and Subscript text syntax.