<s>
Geometric	B-Application
Dimensioning	I-Application
and	I-Application
Tolerancing	I-Application
(	O
GD&T	B-Application
)	O
is	O
a	O
system	O
for	O
defining	O
and	O
communicating	O
engineering	O
tolerances	O
and	O
relationships	O
.	O
</s>
<s>
It	O
uses	O
a	O
symbolic	O
language	O
on	O
engineering	B-Architecture
drawings	I-Architecture
and	O
computer-generated	O
three-dimensional	O
solid	O
models	O
that	O
explicitly	O
describe	O
nominal	O
geometry	O
and	O
its	O
allowable	O
variation	O
.	O
</s>
<s>
GD&T	B-Application
is	O
used	O
to	O
define	O
the	O
nominal	O
(	O
theoretically	O
perfect	O
)	O
geometry	O
of	O
parts	O
and	O
assemblies	O
,	O
to	O
define	O
the	O
allowable	O
variation	O
in	O
form	O
and	O
possible	O
size	O
of	O
individual	O
features	O
,	O
and	O
to	O
define	O
the	O
allowable	O
variation	O
between	O
features	O
.	O
</s>
<s>
Two	O
examples	O
are	O
linear	O
dimensions	O
and	O
feature	B-Application
control	I-Application
frames	I-Application
using	O
a	O
datum	O
reference	O
(	O
both	O
shown	O
below	O
)	O
.	O
</s>
<s>
There	O
are	O
several	O
standards	O
available	O
worldwide	O
that	O
describe	O
the	O
symbols	O
and	O
define	O
the	O
rules	O
used	O
in	O
GD&T	B-Application
.	O
</s>
<s>
The	O
Y14.5	O
standard	O
provides	O
a	O
fairly	O
complete	O
set	O
of	O
rules	O
for	O
GD&T	B-Application
in	O
one	O
document	O
.	O
</s>
<s>
position	B-Application
,	O
flatness	O
,	O
profile	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
BS	B-Application
8888	I-Application
provides	O
a	O
self-contained	O
document	O
taking	O
into	O
account	O
a	O
lot	O
of	O
GPS&V	O
standards	O
.	O
</s>
<s>
The	O
origin	O
of	O
GD&T	B-Application
is	O
credited	O
to	O
Stanley	O
Parker	O
,	O
who	O
developed	O
the	O
concept	O
of	O
"	O
true	B-Application
position	I-Application
"	O
.	O
</s>
<s>
In	O
1940	O
,	O
Parker	O
published	O
Notes	O
on	O
Design	O
and	O
Inspection	O
of	O
Mass	O
Production	O
Engineering	O
Work	O
,	O
the	O
earliest	O
work	O
on	O
geometric	B-Application
dimensioning	I-Application
and	I-Application
tolerancing	I-Application
.	O
</s>
<s>
According	O
to	O
the	O
ASME	O
Y14.5-2009	O
standard	O
,	O
the	O
purpose	O
of	O
GD&T	B-Application
is	O
to	O
describe	O
the	O
engineering	O
intent	O
of	O
parts	O
and	O
assemblies	O
.	O
</s>
<s>
GD&T	B-Application
can	O
more	O
accurately	O
define	O
the	O
dimensional	O
requirements	O
for	O
a	O
part	O
,	O
allowing	O
over	O
50%	O
more	O
tolerance	O
zone	O
than	O
coordinate	O
(	O
or	O
linear	O
)	O
dimensioning	O
in	O
some	O
cases	O
.	O
</s>
<s>
Proper	O
application	O
of	O
GD&T	B-Application
will	O
ensure	O
that	O
the	O
part	O
defined	O
on	O
the	O
drawing	O
has	O
the	O
desired	O
form	O
,	O
fit	O
(	O
within	O
limits	O
)	O
and	O
function	O
with	O
the	O
largest	O
possible	O
tolerances	O
.	O
</s>
<s>
GD&T	B-Application
can	O
add	O
quality	O
and	O
reduce	O
cost	O
at	O
the	O
same	O
time	O
through	O
producibility	O
.	O
</s>
<s>
For	O
basic	O
dimensions	O
,	O
geometric	B-Application
tolerances	I-Application
are	O
indirectly	O
applied	O
in	O
a	O
related	O
Feature	B-Application
Control	I-Application
Frame	I-Application
.	O
</s>
<s>
Engineering	B-Architecture
drawings	I-Architecture
define	O
the	O
requirements	O
of	O
finished	O
(	O
complete	O
)	O
parts	O
.	O
</s>
<s>
Tolerances	O
for	O
the	O
profile	O
symbols	O
are	O
equal	O
bilateral	O
unless	O
otherwise	O
specified	O
,	O
and	O
for	O
the	O
position	B-Application
symbol	O
tolerances	O
are	O
always	O
equal	O
bilateral	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
position	B-Application
of	O
a	O
hole	O
has	O
a	O
tolerance	O
of	O
.020	O
inches	O
.	O
</s>
<s>
+	O
Symbols	O
used	O
in	O
a	O
"	O
feature	B-Application
control	I-Application
frame	I-Application
"	O
to	O
specify	O
a	O
feature	O
's	O
description	O
,	O
tolerance	O
,	O
modifier	O
and	O
datum	O
references	O
Symbol	O
Unicode	O
character	O
Modifier	O
Notes	O
32px|center	O
ⒻU+24BB	O
Free	O
state	O
Applies	O
only	O
when	O
part	O
is	O
otherwise	O
restrained	O
32px|center	O
ⓁU+24C1	O
Least	O
material	O
condition	O
(	O
LMC	O
)	O
Useful	O
to	O
maintain	O
minimum	O
wall	O
thickness	O
32px|center	O
ⓂU+24C2	O
Maximum	B-Application
material	I-Application
condition	I-Application
(	O
MMC	O
)	O
Provides	O
bonus	O
tolerance	O
only	O
for	O
a	O
feature	O
of	O
size	O
32px|center	O
ⓅU+24C5	O
Projected	O
tolerance	O
zone	O
Useful	O
on	O
threaded	O
holes	O
for	O
long	O
studs	O
32px|center	O
ⓈU+24C8	O
Regardless	O
of	O
feature	O
size	O
(	O
RFS	O
)	O
t	O
part	O
of	O
the	O
1994	O
version	O
.	O
</s>
<s>
Technologist	O
GDTP	O
,	O
which	O
provides	O
an	O
assessment	O
of	O
an	O
individual	O
’s	O
ability	O
to	O
understand	O
drawings	O
that	O
have	O
been	O
prepared	O
using	O
the	O
language	O
of	O
Geometric	B-Application
Dimensioning	I-Application
&	O
Tolerancing	O
.	O
</s>
<s>
Exchange	O
of	O
geometric	B-Application
dimensioning	I-Application
and	I-Application
tolerancing	I-Application
(	O
GD&T	B-Application
)	O
information	O
between	O
CAD	B-Application
systems	O
is	O
available	O
on	O
different	O
levels	O
of	O
fidelity	O
for	O
different	O
purposes	O
:	O
</s>
<s>
In	O
the	O
early	O
days	O
of	O
CAD	B-Application
,	O
exchange-only	O
lines	O
,	O
texts	O
and	O
symbols	O
were	O
written	O
into	O
the	O
exchange	O
file	O
.	O
</s>
<s>
GD&T	B-Application
presentation	O
:	O
On	O
a	O
next	O
higher	O
level	O
the	O
presentation	O
information	O
is	O
enhanced	O
by	O
grouping	O
them	O
together	O
into	O
callouts	O
for	O
a	O
particular	O
purpose	O
,	O
e.g.	O
</s>
<s>
GD&T	B-Application
representation	O
:	O
Unlike	O
GD&T	B-Application
presentation	O
,	O
the	O
GD&T	B-Application
representation	O
does	O
not	O
deal	O
with	O
how	O
the	O
information	O
is	O
presented	O
to	O
the	O
user	O
but	O
only	O
deals	O
with	O
which	O
element	O
of	O
a	O
shape	O
of	O
a	O
product	O
has	O
which	O
GD&T	B-Application
characteristic	O
.	O
</s>
<s>
A	O
system	O
supporting	O
GD&T	B-Application
representation	O
may	O
display	O
GD&T	B-Application
information	O
in	O
some	O
tree	O
and	O
other	O
dialogs	O
and	O
allow	O
the	O
user	O
to	O
directly	O
select	O
and	O
highlight	O
the	O
corresponding	O
feature	O
on	O
the	O
shape	O
of	O
the	O
product	O
,	O
2D	O
and	O
3D	O
.	O
</s>
<s>
Ideally	O
both	O
GD&T	B-Application
presentation	O
and	O
representation	O
are	O
available	O
in	O
the	O
exchange	O
file	O
and	O
are	O
associated	O
with	O
each	O
other	O
.	O
</s>
<s>
Then	O
a	O
receiving	O
system	O
can	O
allow	O
a	O
user	O
to	O
select	O
a	O
GD&T	B-Application
callout	O
and	O
get	O
the	O
corresponding	O
feature	O
highlighted	O
on	O
the	O
shape	O
of	O
the	O
product	O
.	O
</s>
<s>
An	O
enhancement	O
of	O
GD&T	B-Application
representation	O
is	O
defining	O
a	O
formal	O
language	O
for	O
GD&T	B-Application
(	O
similar	O
to	O
a	O
programming	O
language	O
)	O
which	O
also	O
has	O
built-in	O
rules	O
and	O
restrictions	O
for	O
the	O
proper	O
GD&T	B-Application
usage	O
.	O
</s>
<s>
GD&T	B-Application
validation	O
:	O
Based	O
on	O
GD&T	B-Application
representation	O
data	O
(	O
but	O
not	O
on	O
GD&T	B-Application
presentation	O
)	O
and	O
the	O
shape	O
of	O
a	O
product	O
in	O
some	O
useful	O
format	O
(	O
e.g.	O
</s>
<s>
a	O
boundary	B-Algorithm
representation	I-Algorithm
)	O
,	O
it	O
is	O
possible	O
to	O
validate	O
the	O
completeness	O
and	O
consistency	O
of	O
the	O
GD&T	B-Application
information	O
.	O
</s>
<s>
GD&T	B-Application
representation	O
information	O
can	O
also	O
be	O
used	O
for	O
the	O
software	O
assisted	O
manufacturing	O
planning	O
and	O
cost	O
calculation	O
of	O
parts	O
.	O
</s>
