Point Locations (Virtual Sharps)

The names for dimensioning methods within ASME Y14.5-2009 often do not match the common names.  For example, what most of us call ordinate dimensioning is officially labelled as rectangular coordinate dimensioning.  This can make finding information about certain dimensioning methods hard to find within the standard.

One dimensioning method that is particularly difficult to find is point location.  A point location is where a point is located by the intersection of extension lines only.  The method is known by so many other names.

• theoretical sharp corner
• theoretical corner
• theoretical sharp
• apex
• intersect
• intersection
• intersection point
• imaginary point
• virtual sharp
• and likely others as well
  

SolidWorks uses the term virtual sharp.  SolidWorks offers a list of options for the delineation of virtual sharp (i.e., point location), which is found at Tools pulldown>Options...>Document Properties tab>Dimensions heading>Virtual Sharps subheading.  The only method supported by ASME Y14.5-2009 is the use of intersecting extension lines from two surfaces; so called witness in SolidWorks.

The standard does not require any other identifier or labelling.  Yet many of us do feel compelled to add some sort of label to the dimension, using one of the above terms or their initials.  A label does add clarity, particularly when the scale of a view makes display of a point location hard to read.

I covered this topic once before from a slightly different perspective in this article: Virtual Sharps.  That article includes instructions on how to create a virtual sharp in SolidWorks drawings.

Author: fcsuper

As a drafter, mechanical designer and CAD engineer, I've been in the mechanical design field since 1991. For the first 8 years of my career, I was an AutoCAD professional. I utilized AutoLISP and many other AutoCAD customization features to streamline drafting activities for 6+ drafters and designers. I authored several custom functions, one of which was published in the March 1997 issue of Cadalyst Magazine. Since 1998, I've been used SolidWorks non-stop. I've worked to utilize the SolidWorks' user environment to simplify drafting and design activities for 20+ engineers. I've created this website to provide current information about SolidWorks from a variety of contributors. More recently, I am now employed by Dassault Systemes as SOLIDWORKS Sr. Product Definition Manager to improve drawing, annotation and MBD related areas. View all posts by fcsuper