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| What
Is GD&T? |
GD&T
stands for geometric dimensioning and
tolerancing. It is a system of symbols, rules
and definitions used to define the geometry of
mechanical parts.
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GD&T
is one of the most powerful tools available that
can improve quality, reduce cost and shorten
delivery time. All of this is possible when the
concurrent engineering team is involved with the
creation of the drawing. The drawing is a common
thread that ties these groups together. They all
are involved with the engineering drawing. GD&T
on the drawing must first and foremost capture
design intent. However, the best design in the
world is worthless if it cannot be produced.
That is why it is necessary for
production/vendors and quality to be involved
with the requirements that are placed on the
drawing. When they are not involved, the
drawings often have overly tight tolerances and
result in non-producible parts. At least not
producible at the quality level, cost and
timeliness expected by industry.
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Nearly every
company in the United States and many companies
around the world use the ASME Y14.5M-1994
standard on GD&T. There is an ISO standard but
it is in a state of flux. Because of this the
Y14.5 standard is recognized and used around the
world.
In
short, GD&T is:
- Symbols
- Rules
- Vocabulary
- Mathematical
definition (ASME Y14.5.1)
- A National
Standard (ASME Y14.5M-1994)
- An
International Standard (ISO 1101)
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There is no other
standardized way to control the geometry of
parts. The old methods were never standardized.
Many people thought they knew what the old
method meant. The problem was that many people
interpreted the drawing differently. GD&T is
standardized and mathematized which means that
anyone who knows the Standard, knows what the
drawing means. GD&T is today's Print
Reading. Anyone who creates, approves or uses
the drawing should know how to read the drawing.
In today's world, if you do not know GD&T, you
do not know how to read! |
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Max
says -
Use
GD&T to effectively communicate product specs to
ensure the part drawn, is the part
made.
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