NOTICE :

1
NOTICE This presentation is part of a
presentation that was given at the March 2008
Lunch N Learn at JH Machine Tools in
Charlotte. The presentation is meant to be viewed
with the narration and detailed explanation of
the presenter.
2
Understanding True Position
Best Fit of Bore Pattern
A portion of the True Position Part III LNL
presentation.
3
True Position of the Three Holes
3x
10
10
10
Ø 0.2 A B C
Ø 0.1 A
C
10
20
-A-
B
4
The Top tier controls the feature positions
relative to the Datum Reference Frame. The
tolerance zone is FULLY CONSTRAINED to the
Specified Datums. This ensures the holes are
located properly on the part.
This is a True Position with a COMPOSITE
TOLERANCE.
Ø 0.2 A B C
Ø 0.1 A
The Bottom tier controls the pattern of holes
to themselves, without positional or rotational
constraints, in this case. This ensures that the
pattern itself will mate with the joining parts
hole pattern.
5
Top Tier
3x
10
10
10
Ø 0.2 A B C
C
10
20
-A-
B
6
Top Tier Tolerance Zone Location
3x
10
10
10
Ø 0.2 A B C
C
10
20
-A-
B
7
Bottom Tier
3x
10
10
Ø 0.1 A
10
-A-
8
Bottom Tier Zone Location
3x
10
10
Ø 0.1 A
Dia 0.1
10
-A-
9
Bottom Tier Zone Location
3x
Ø 0.1 A
Dia 0.1
-A-
10
Bottom Tier Zone Location
3x
Ø 0.1 A
Dia 0.1
-A-
11
Bottom Tier Zone Location
3x
Ø 0.1 A
Dia 0.1
-A-
12
An Example Here are ACTUAL center points. Are
they in Spec?
Lets Check the Top Tier.
-A-
13
An Example Here are ACTUAL center points. Are
they in Spec?
Good!
Ø 0.2 A B C
-A-
14
In Calypso
15
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An Example Here are ACTUAL center points. Are
they in Spec?
Ø 0.2 A B C
Lets Check the Bottom Tier.
-A-
20
An Example Here are ACTUAL center points. Are
they in Spec?
Ø 0.2 A B C
Ø 0.1 A
-A-
21
An Example Here are ACTUAL center points. Are
they in Spec?
Ø 0.2 A B C
Ø 0.1 A
-A-
22
An Example Here are ACTUAL center points. Are
they in Spec?
Ø 0.2 A B C
Ø 0.1 A
-A-
23
An Example Here are ACTUAL center points. Are
they in Spec?
Ø 0.2 A B C
Ø 0.1 A
-A-
24
An Example Here are ACTUAL center points. Are
they in Spec?
BAD!
Ø 0.2 A B C
Ø 0.1 A
-A-
25
In Calypso
26
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Ø 0.2 A B C
Ø 0.1 A