Asee peer logo

Clarifications of a Datum Axis or Centerplane Specifying in Maximum Material Condition of Geometric Dimensioning and Tolerancing

Download Paper |


2013 ASEE Annual Conference & Exposition


Atlanta, Georgia

Publication Date

June 23, 2013

Start Date

June 23, 2013

End Date

June 26, 2013



Conference Session

Implementing Active Learning in Mechanical Engineering Technology

Tagged Division

Engineering Technology

Page Count


Page Numbers

23.289.1 - 23.289.7



Permanent URL

Download Count


Request a correction

Paper Authors


Cheng Y. Lin P.E. Old Dominion University

visit author page

Dr. Lin is a professor and program director of Mechanical Engineering Technology at Old Dominion University. He received his Ph.D. of Mechanical Engineering from Texas A&M University in 1989, and is a registered professional engineer in Virginia. Dr. Lin has expertise in automation control, machine design, CAD/CAM, CNC, geometric dimensioning and tolerancing, and robotics. He has published sixteen journal papers in the areas of robotics, automation, and GD&T.
He has been active in the technology application research and teaching training courses for Virginia's Applied Technology and Professional Development Center (VATPDC).

visit author page


Jennifer Grimsley Michaeli P.E. Old Dominion University

visit author page

Dr. Jennifer Michaeli is an assistant professor in the Mechanical Engineering Technology Program at the Department of Engineering Technology of Old Dominion University. She received her Ph.D. in Mechanical Engineering from Old Dominion University, her M.Sc. in Ocean Systems Management from Massachusetts Institute of Technology, and her B.Sc. in Naval Architecture and Marine Engineering from Webb Institute. Dr. Michaeli has over fifteen years practical work experience in the government and private industry as a Naval Architect and program manager where she oversaw the design, construction and testing of a wide range of high performance marine vehicles and associated technologies for the United States and foreign navies. Dr. Michaeli has expertise in the design, construction, testing and fielding of advanced combatant vessels and associated technologies. She has taught courses in Engineering, Naval Architecture, and Computer Aided Design.
Dr. Michaeli is a past recipient of the ASNE Rosenblatt Young Engineer of the Year Award and the U.S. Navy’s ADM Melville Award. She is a registered professional engineer in Virginia. She is a member of ASEE, ASNE, RINA, and SNAME.

visit author page


Mileta Tomovic Old Dominion University

visit author page

Dr. Tomovic is serving as the chair of Engineering Technology Department, Old Dominion University, Norfolk, Va. Prior to joining ODU Dr. Tomovic was faculty member at Purdue University, West Lafayette, Indiana. While at Purdue University, Dr. Tomovic held the position of W. C. Furnas chaired professor at the College of Technology. He also served as special assistant to the dean for Advanced Manufacturing, co-director for Product Lifecycle Management Center of Excellence, director of Digital Enterprise Center, and department head of Mechanical Engineering Technology Department. Dr. Tomovic is also Honorary Professor at Beihang University, Beijing, China. Dr. Tomovic received B.S. in Mechanical Engineering from the University of Belgrade, Yugoslavia, M.S. in Mechanical Engineering from the Massachusetts Institute of Technology, and Ph.D. in Mechanical Engineering from the University of Michigan. Dr. Tomovic co-authored one textbook on materials and manufacturing processes that has been adopted by over 50 national and international institutions of higher education. In addition, he has authored or co-authored over 60 papers in journals and conference proceedings, focused on applied research related to product lifecycle management, design and manufacturability, system dynamics and controls, and engineering education. Dr. Tomovic delivered over 20 invited presentations nationally and internationally. He has authored and/or co-authored four patents, and over 100 technical reports on practical industrial problems related to product design and manufacturing process improvements.

visit author page

Download Paper |


Clarifications of a Datum Axis or Centerplane Specifying in Maximum Material Condition of Geometric Dimensioning and Tolerancing[Abstract]In Geometric Dimensioning and Tolerancing (GD&T) the datum is defined as atheoretically exact plane, point, or axis from which a dimensional measurement is made.Datum features include flat datum features, datum targets (3-2-1 Rule), and datum axes.While flat datum features and datum targets have been clearly defined, the author hasexperienced learning difficulties among students in defining a datum axis usingMaximum Material Condition (MMC). The same problems occur when giving GD&Ttraining to engineers working in local industries. This paper presents an approach toresolve this issue.When a feature of size (FOS) is specified as a datum feature, it results in an axis or acenter plane as a datum. Figure 1 (Please see the figure attached in the second page ofthis abstract) shows a datum axis specified as “A○” (MMC). Since the MMC of the FOS Mis φ2.0050”, the fixed gage size φ2.0050” (showing on the very right side of Figure 1)which defines the datum axis is easily understood. However, the datum axis “A○” Mspecified in Figure 2 causes a problem to the students. Most students and engineers stilluse the same gage size φ2.0050” to define the datum axis mainly because of the samesymbol “A○”. According to the ASME 14.5M standards, the fixed gage size to represent Mthis datum axis should be φ2.0070” (showing on the very right side of Figure 2), which isthe Virtual Condition (VC) of the external feature (φ2.0050”+ φ0.0020”). To avoid thisconfusion, it’s suggested by the author to use another symbol “A○”, as showing in VFigure 3, to specify the datum axis when the FOS for the datum also includes a GD&Ttolerance in MMC. “○” represents the Virtual Condition of the datum Axis. Examples Vapplied in the external and internal features will be given. A thorough rationalization ofusing “○” in a datum axis will be discussed. VThe suggestion of using “○” in specifying a datum axis and center plane in MMC has Vbeen brought up for discussion in classes and training sessions. Almost all studentsagreed that this will certainly clarify the issues in specifying a datum axis or center plane. Figure 1: A Datum Axis Using A○ to Define the Datum Axis MFigure 2: A Datum Axis Associated with a Feature Control Frame to Define the Datum Axis Figure 3: A Suggested Drawing to Replace the Part Showing in Figure 2

Lin, C. Y., & Michaeli, J. G., & Tomovic, M. (2013, June), Clarifications of a Datum Axis or Centerplane Specifying in Maximum Material Condition of Geometric Dimensioning and Tolerancing Paper presented at 2013 ASEE Annual Conference & Exposition, Atlanta, Georgia. 10.18260/1-2--19303

ASEE holds the copyright on this document. It may be read by the public free of charge. Authors may archive their work on personal websites or in institutional repositories with the following citation: © 2013 American Society for Engineering Education. Other scholars may excerpt or quote from these materials with the same citation. When excerpting or quoting from Conference Proceedings, authors should, in addition to noting the ASEE copyright, list all the original authors and their institutions and name the host city of the conference. - Last updated April 1, 2015