P. H. O
NUST SMME
Advance Workshop Practice Lab
Geometric dimensioning and tolerancing
Ref: _________________
Level: UG
Mode: Practical
Time: 03 Hours
Course: ME-223 Advance Workshop
Group: ______
TITLE
1.
Geometric Dimensioning and Tolerancing (GD&T)- Metrology Practice.
Introduction
2.
GD&T is an international language that is used on engineering drawings to accurately describe a part. It
defines a part based upon how it functions in the final product.
3.
GD&T increases tolerances with cylindrical tolerance zones and allows additional or bonus tolerances.
GD&T allows the designer to communicate more effectively and eliminates confusion during inspection.
Objective:
4.
To introduce proper use of GD&T symbols, reading and interpretation of engineering drawings,
techniques for determining part adherence to design requirements and workmanship standards. measuring
techniques of common instruments used in a workshop.
Requirements
5.
Following items are required for conduct of this demo and practical exercise:
a.
Vernier caliper.
b.
Micro meter
c.
Dial Indicator with stand
d.
Go, No Go Gauges
e.
Feeler Gauge
f.
GD&T Drawings of the specimen job without dimensions.
g.
Lathe and Milling Machine
h.
Sample job or specimen as per the drawing.
Procedure
6. Students will acquire different techniques to determine geometrical characteristics of a part/specimen
surfaces using different measuring instruments or gauges. Go/No-Go gauges will also be used to ensure
that internal/external features of size (FOS) will assemble with one another. Go gauge verifies part
diameter does not exceed MMC size while NO-Go gauge verifies that any two points check is equal to
or greater than LMC. The following geometrical characteristics will be practiced.
a. Straightness
b. Flatness
c. Circularity or Roundness
d. Cylindricity
e. Angularity
f.
Perpendicularity
g. Parallelism
h. Positioning
i.
Concentricity
j.
Circular runout
k. Total runout
l.
7.
PCD
Carry out above geometric characteristic measurements of the specimen to as accurate as possible
level and mark them on the drawing.
Special Instructions
8.
Each reading must be taken at least twice.
9.
Ensure that the instruments are calibrated and corrected against zero error.