NPS GENERAL SPECIFICATION

Specification Engineering Common Product

Number Issue Date Code Code Page Total

NPS51218 3 94/Oct - - 1 39

NPS51218

ELECTRONIC DATA TRANSFER (EDT)

FILE GENERIC REQUIREMENTS

PRODUCT ASSURANCE COMPONENT ENGINEERING

Issued by Approved by Technical Content

Documentation Services Controlled by

P.R. Maxwell E. Millward K. White

Issue No 3 NPS51218

Issue Date Description

1 92/May Initial issue.

2 92/Dec Minor rewording changes throughout document.
3 94/Oct Corrections to change descriptions & addition of
tolerance formats for plastics, die cast parts and Class 2
tolerances for Sigma 3 sheet metal parts added. Changes
affected; NPS Sect. 1.1, 1.2, 3, 3.1.1, 3.1.2, 3.1.3, 3.1.3.2,
3.2, 3.3.1, 3.4, 3.4.1, 3.4.2, 3.4.9, 3.4.9.1, 3.4.9.2, 3.4.9.3,
3.5.1, 3.5.2, 3.5.3, 3.5.7, 3.5.8, 6.1, 6.1.2.
Guideline Sect. 1.1, 1.2, 2.0, 3.0, 3.2, 4.3, 4.5, 4.7, 4.8,
6.2, 6.4, 6.7, 6.12, 6.13, 7.2, 7.3, 7.6, 7.7, 10.1, 10.2, 10.8,
10.9, 10.11, 10.13, 11.1, 11.2, 11.6.

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Issue No 3 NPS51218

Contents
Section Description Page

GLOSSARY OF TERMS...............................................................................5
1. GENERAL......................................................................................................7
1.1 Scope.............................................................................................................. 7
1.2 Application..................................................................................................... 7
2. APPLICABLE DOCUMENTS ..................................................................... 8
3. REQUIREMENTS......................................................................................... 8
3.1 Sheet Metal Parts ........................................................................................... 9
3.1.1 Order of Precedence .......................................................................................9
3.1.2 Sheet Metal Flat Patterns (Tolerance) ............................................................9
3.1.3 Formed Sheet Metal (Tolerances) ................................................................11
3.2 Sheetmetal Assemblies ................................................................................ 12
3.2.1 Fastener Installation .....................................................................................13
3.3 Machined Parts............................................................................................. 14
3.3.1 Order of Precedence .....................................................................................14
3.3.2 Machined Piece Parts (Tolerances) ..............................................................15
3.3.3 Machine Threads ..........................................................................................16
3.4 Injection Molded Plastic Parts ..................................................................... 17
3.4.1 Molded Plastic Piece Parts (Commercial Tolerances) .................................17
3.4.2 Molded Plastic Piece Parts (Tolerances) ......................................................17
3.4.3 Surface Finish ..............................................................................................18
3.4.4 Post Molding Machine Operations (Tolerances) .........................................18
3.4.5 Location of Gates .........................................................................................18
3.4.6 Location of Ejectors .....................................................................................18
3.4.7 Feature Definition ........................................................................................18
3.4.8 Fillets and Rounds ........................................................................................18
3.4.9 Drafts ............................................................................................................19
3.4.10 Flash .............................................................................................................19
3.4.11 Witness Lines ...............................................................................................19
3.5 Die Cast Parts............................................................................................... 20
3.5.1 Die Cast Parts (Commercial Tolerances) .....................................................20
3.5.2 Die Cast Parts (Tolerances) .........................................................................20
3.5.3 Location of Gates .........................................................................................21
3.5.4 Location of Ejectors......................................................................................21
3.5.5 Feature Definition ........................................................................................21
3.5.6 Burrs and Sharp Edges .................................................................................21
4. SYMBOLS................................................................................................... 22
4.1 Weld Symbols.............................................................................................. 22
5. INCOMPLETE FEATURES....................................................................... 22

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Issue No 3 NPS51218

Contents
Section Description Page

5.1 General......................................................................................................... 22
6. DATUMS..................................................................................................... 22
6.1 General......................................................................................................... 22
6.1.1 Single Features .............................................................................................23
6.1.2 Groups of Features .......................................................................................23
7. INSPECTION.............................................................................................. 24
7.1 Part Verification........................................................................................... 24
7.2 Specific Requirements ................................................................................. 24
7.3 Part Measurement ........................................................................................ 24
APPENDIX A Design Guideline...........................................................25

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Issue No 3 NPS51218

GLOSSARY OF TERMS

ADCI American Die Casting Institute. Their standard is used to provide

default tolerances for die cast parts.

CAD Computer Aided Design. Usually refers to IGES compatible

software used to design or view parts.

CAM Computer Aided Manufacturing. Usually refers to IGES

compatible software used to extract information required to
fabricate parts, for example, software used to unfold sheet metal 3D
models or extract machine tool paths for machined parts.

IGES Initial Graphics Exchange Standard. The file format used to transfer
design information, 3D model and 2D drawing file, from NT to
suppliers.

NPS Northern Procurement Specification

NT Northern Telecom

PA Physical Agreement. A review step in the design-to manufacture

process that determines the readiness of the design for release to
manufacturing. In the context of NPS51218 the PA is also used to
determine design file content and identify all areas where the 3D
model and the 2D file do not, or can not, meet specific require-
ments, and take appropriate action to either correct the design files
or ensure that any exceptions are sent to NT, Product Assurance and
Component Engineering (PACE), for review and potential inclu-
sion in the NPS.

SPI Society of the Plastics Industry. Their standard is used to provide

default tolerances for plastic parts.

SHALL Identifies requirements that are mandatory.

SHOULD Identifies requirements that are good practice and preferred.

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Issue No 3 NPS51218

GLOSSARY OF TERMS (continued)

2D File A drawing file which contains notes and explanatory detail, not
included in the 3D model file, necessary for fabrication.

3D Model 3 dimensional model. This file, in IGES format, carries the physical
shape and 1:1 dimensional information which can be accessed by
IGES compatible design or fabrication software.

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Issue No 3 NPS51218

1. GENERAL
1.1 Scope
This general specification defines generic requirements for the 2D and
3D electronic files used to convey mechanical fabrication information
from design to manufacturing.
Complete information necessary to fabricate a given part or assembly
resides collectively in the following three places:
- 3D model, a three dimensional model of the part or
assembly (model scale is 1:1)

- 2D file, a two dimensional graphic representation of the part or

assembly with notes

- NPS51218, the Northern procurement specification containing

generic fabrication information
All three sources are required by the suppliers of Northern Telecom in
order to manufacture a given part or assembly using the Electronic
Design Transfer Process.
1.2 Application
This general specification provides rules for interpreting 2D files and 3D
models and is for use by all those involved in the design transfer
process. The design guideline (Appendix A) shall be used by those
preparing the 2D files and 3D models that will be interpreted according
to NPS51218.
Some requirements are specific to a particular type of part or assembly.
This specification includes specific requirements for sheet metal parts,
sheet metal assemblies, machined parts, injection molded parts, and cast
parts.
This specification applies only to those parts or assemblies which
specifically reference NPS51218 on the associated 2D file, and only to
processes specifically covered.

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Issue No 3 NPS51218

2. APPLICABLE DOCUMENTS
The following documents, of the issue in effect on the date of the
purchase order, form part of this NPS to the extent specified herein:
151.02, NT Corporate Handbook, Welding Symbols
ANSI B1.1, American National Standards Institute, Unified Screw
Threads
ANSI Y14.5M-1982, American National Standards Institute,
Dimensioning and Tolerancing
ISO 965, International Organization of Standardization, General
Purpose Metric Screw Threads
ISO 4759, International Organization of Standardization, Tolerances for
Fasteners
American Die Casting Institute, Inc. (ADCI - E12 - 83) E Series Product
Standards for Die Casting.
Standards and Practices of Plastic Molders, SPI Publication, 1993

3. REQUIREMENTS
Unless specifically identified in the applicable 2D file, tolerances shall
be as specified in Section 3. Location and tolerances are with respect to
the datum shown in the 2D file. The 3D model describes the unfinished
part. Finish (plating or paint) thickness must be allowed for when
measuring the finished part.

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 Issue No 3 NPS51218

3.1 Sheet Metal Parts

3.1.1 Order of Precedence
The 3D model is intended to communicate the design to the supplier.
The information in the model is interpreted using this specification and
the 2D file.

Change information may be provided as an aid to the supplier in

modifying existing tooling / programming to produce the new issue of
the design. If there is conflict between the change information and the
3D model, the 3D model is to take precedence over the change notes.

Except as noted in the previous paragraph, in case of a conflict of

information the order of precedence shall be:

a) 2D file
b) This specification
c) 3D Model
3.1.2 Sheet Metal Flat Patterns (Default Tolerance)
Imperial
Dimension Range (in) Tolerance (in)
Feature location 0 - 23.999 ± 0.005
(from datum, on any flat surface) 24 - 47.999 ± 0.010
or 48 - 95.999 ± 0.015
Feature size 96+ Special case, refer to drawing
Round hole size (Note 1) 0 -3 dia ± 0.003
Angles ± 1°
Metric
Dimension Range (mm) Tolerance (mm)
Feature location 0 - 500 ± 0.1
(from datum, on any flat surface) +500 - 1000 ± 0.2
or +1000 - 2500 ± 0.4
Feature size +2500 special case, refer to drawing
Round hole size (Note 1) 0 - 100 dia ± 0.1
Angles ± 1°
Note 1: Diameter to be measured at burnished portion (punched side) of punched hole cross-section.

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Issue No 3 NPS51218

Sheet Metal Flat Patterns (Class B Tolerances)

To utilize class B tolerances the 2D file must have a note referring to Class B tolerances.
Imperial
Dimension Range (in) Tolerance (in)
Feature location 0 - 11.999 ± 0.005
(from datum, on any flat surface) 12 - 23.999 ± 0.010
or 24 - 47.999 ± 0.015
Feature size 48 - 95.999 ± 0.025
96 + Special case, refer to drawing
Round hole size (Note 1) 0 - 0.249 dia ± 0.003
0.250 - 0.499 ± 0.005
0.500 + ± 0.007
Countersink diameter (Note 2) 0 - 0.249 ± 0.006
0.250 - 0.499 ± 0.008
0.500 + ± 0.010
Metric
Dimension Range (mm) Tolerance (mm)
Feature location 0 - 299 ± 0.1
(from datum, on any flat surface) 300 - 599 ± 0.25
or 600 - 1199 ± 0.4
Feature size 1200 - 2399 ± 0.6
2400 + Special case, refer to drawing
Round hole size (Note 1) 0 - 5.9 dia ± 0.07
6 - 11.9 ± 0.1
12 + ± 0.2
Countersink diameter (Note 2) 0 - 5.9 ± 0.15
6 - 11.9 ± 0.2
12 + ± 0.25
Note 1: Diameter to be measured at burnished portion (punched side) of punched hole cross-section.
Note 2: For countersinks formed with a press stroke. For machined features see section 3.3
Note 3: See Guideline section 7.7 on page 33 for application

3.1.2.1 Feature Definition (Sheetmetal Flat Patterns)

Features are edges, lances, holes, dimples, extrusions, and so on. Refer
to Section 6 for feature location.

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 Issue No 3 NPS51218

3.1.3 Formed Sheet Metal (Tolerances)

Imperial
Dimension Range (in) Tolerance (in)
Across bends (Note 2 & 3) 0 - 23.999 ± 0.020 across first 1 or 2 bends
(material thickness ≤ 0.090 in) ± 0.010 additional / bend thereafter
(96 in maximum bend length)
24+ refer to drawing
Across bends (Note 2 & 3) 0 - 23.999 ± 0.020 across first bend
(material thickness > 0.090 in) ± 0.015 additional / bend thereafter
(96 in maximum bend length)
24+ refer to drawing
Jogs 2 material thickness ± 0.010
maximum
Bosses/lance height ± 0.010
Angles all ± 1°
Flatness (Note 1) 0.0025 X maximum surface
dimension = tolerance
Metric
Dimension Range (mm) Tolerance (mm)
Across bends (Note 2 & 3) 0 - 500 ± 0.5 across first 1 or 2 bends
(material thickness ≤ 2 mm) ± 0.2 /bend thereafter
(2500 mm maximum bend length)

500+ refer to drawing

Across bends (Note 2 & 3) 0 - 500 ± 0.5 across first bend
(material thickness > 2 mm) ± 0.4 /bend thereafter
(2500 mm maximum bend length)

500 + refer to drawing

Jogs 2 material thickness ± 0.3
maximum
Bosses/lance height ± 0.3
Angles all ± 1°
Flatness (Note 1) 0.0025 X maximum surface
dimension = tolerance
Note: 1. Flatness shall be interpreted using ANSI standard Y14.5M-1982, Section 6.4.2.
Note: 2. Feature tolerances established in the flat pattern continue to apply after forming for features on
a single flat surface. The flat pattern tolerance for a surface shall be applied from the feature
closest to the higher ranking datum (datum A before datum B before datum C) unless a feature
on a flat surface is dimensioned.
If a feature on a flat surface is dimensioned, flat pattern tolerances for the surface shall be
applied from the dimensioned feature closest to the higher ranking datum (datum A before
datum B before datum C).
Note: 3. Feature tolerance across bends is dependant on the bend tolerance only and is not added to
the flat pattern tolerance.

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Issue No 3 NPS51218

3.1.3.1 Inside Bend Radii

Unless otherwise specified on the 2D file, the maximum inside bend
radius is material thickness.
3.1.3.2 Formed Features
The size of all formed features shall be fully specified in the 2D file.
Examples of formed features are lances, dimples, extrusions, and so on.
3.1.3.3 Burrs and Sharp Edges
Remove all burrs and sharp edges, unless otherwise specified on the 2D
file.
3.1.3.4 Machine Operations (Tolerances)
Refer to Section 3.3 (Machined Parts) for tolerances on machine
operations on sheet metal parts.
3.2 Sheetmetal Assemblies
Dimension Tolerance

Flatness (Note 1): 0.0025 X Maximum Surface Dimension

= Tolerance

Note: 1. Flatness shall be interpreted using ANSI standard

Y14.5M-1982, Section 6.4.2.

Flatness

NPS51218 Sec.3.2 0.55 mm

Tolerance
= 0.0025 x 220
= 0.55 mm

220 mm

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Issue No 3 NPS51218

3.2.1 Fastener Installation

Fasteners, such as clinch fasteners and rivets, may not always be
illustrated. The position of the fastener and the direction of insertion is
to be clearly indicated in the 2D file.
The following are typical examples of how fasteners may be shown.

Actual Representation Representation in 2D File

View
Example 1 — Clinch Nut
+0.003
0.187 -0.000 Dia
Install Item 20
Insert from Far Side
Direction of Insertion NPS51218 Sec.3.2.1a

Note: In the text "Item 20", 20 is an item number referring to a fastener

table. A fastener table on each 2D file lists all fasteners used
with their CPC and description.

Actual Representation Representation in 2D File

View
Example 2 — Clinch Standoff
+0.003
0.213 -0.000 Dia
Install Item 30
Insert from Far Side
NPS51218 Sec.3.2.1b
Direction of Insertion

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Issue No 3 NPS51218

3.3 Machined Parts

Features include edges, holes, counterbores, slots and grooves where a
center line is indicated, walls, edges, and so on. Refer to Section 6 for
feature location.
3.3.1 Order of Precedence
The 3D model is intended to communicate the design to the supplier.
The information in the model is interpreted using this specification and
the 2D file.

Change information may be provided as an aid to the supplier in

modifying existing tooling / programming to produce the new issue of
the design. If there is conflict between the change information and the
3D model, the 3D model is to take precedence over the change notes.

Except as noted in the previous paragraph, in case of a conflict of

information the order of precedence shall be:

a) 2D file
b) This specification
c) 3D Model

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 Issue No 3 NPS51218

3.3.2 Machined Piece Parts (Tolerances)

Imperial
Dimension Range (in) Tolerance (in)
Feature location (from datum) 0 - 11.999 ± 0.005
or 12 - 23.999 ± 0.010
Feature size 24+ Refer to drawing
Perpendicularity 0.002 X dimension from
edge = tolerance
Flatness (Note 2) 0.001 X maximum surface
dimension = tolerance
Roughness (surface finish) 63 microinches maximum
Angles (where angles are specified) ± 1°
Circular (Note 1) ± 0.005
Metric
Dimension Range (mm) Tolerance (mm)
Feature location (from datum) 0 - 300 ± 0.1
or +300 - 600 ± 0.2
Feature size +600 refer to drawing
Perpendicularity 0.002 X dimension from edge
= tolerance
Flatness (Note 2) 0.001 X maximum surface
dimension = tolerance
Roughness (surface finish) 1.6 micrometers maximum
Angles (where angles are specified) ± 1°
Circular (Note 1) ± 0.1
Note 1: Circular features with an arc less than or equal to 180° shall have the specified tolerance applied to the
radius. All circular features with an arc greater than 180° shall have the specified tolerance applied to
the diameter.
Note 2: Flatness shall be interpreted using ANSI standard Y14.5M-1982, Section 6.4.2.

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Issue No 3 NPS51218

3.3.2.1 Inside Edges

Inside edges shown as sharp may be radiused to 0.005 inch (imperial) or
0.1 mm (metric) maximum.
3.3.2.2 Outside Edges
Outside edges shown as sharp are to be broken unless otherwise
specified on the 2D file. Chamfer on these edges shall not exceed
0.02 inch X 45° (imperial) or 0.5 mm X 45° (metric). Burrs are to be
removed.
3.3.3 Machine Threads
3.3.3.1 Modelling
All tapped holes shall be modeled as the tap drill size for machined parts
and lead hole size for cast parts, according to thread class. External
threads shall be modeled to the major diameter of the applicable thread
size.
3.3.3.2 Thread Classification
Unless otherwise stated on the 2D file, unified machine threads shall be
fit Class 2, in accordance with ANSI B1.1 and are indicated in the
2D file. For example 0.138-32 UNC-2B. ISO metric threads shall be
"medium fit" tolerance class 6H (internal) and 6g (external) in
accordance with ISO 4759. For example M8 x 1.25 - 6g.

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Issue No 3 NPS51218

3.4 Injection Molded Plastic Parts

3.4.1 Molded Plastic Piece Parts (Commercial Tolerances)
The 3D model is intended to communicate the design to the supplier.
The information in the model is interpreted using this specification and
the 2D file.

Change information may be provided as an aid to the supplier in

modifying existing tooling / programming to produce the new issue of
the design. If there is conflict between the change information and the
3D model, the 3D model is to take precedence over the change notes.

Except as noted in the previous paragraph, in case of a conflict of

information the order of precedence shall be:

a) 2D file
b) This specification
c) 3D Model
d) Society of the Plastics Industry Inc (SPI) publication,
Standards & Practices of Plastic Molders, 1993 edition.
3.4.2 Molded Plastic Piece Parts (Tolerances)
Unless otherwise specified on the 2D file or in this specification, parts
shall be manufactured in accordance with the commercial tolerances of
the Society of the Plastics Industry Inc (SPI) publication, Standards
& Practices of Plastic Molders, 1993 edition.
Dimension Tolerance
Angles ± 1°
Fillets shown in model ± 25% of radius
Circular (Note) ± 0.005 inches (± 0.1 mm)
Note: Circular features with an arc less than or equal to 180° shall
have the specified tolerance applied to the radius. All circular
features with an arc greater than 180° shall have the specified
tolerance applied to the diameter.
3.4.2.1 Inside Corners and Edges
Unless otherwise specified on the 2D file, inside corners and edges
shown as sharp shall have a radius of 0.01 to 0.02 inch (imperial) or
0.2 to 0.5 mm (metric).

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Issue No 3 NPS51218

3.4.2.2 Outside Corners and Edges

Outside corners and edges shown as sharp shall have a maximum radius
of 0.01 inch (imperial) or 0.2 mm (metric). This does not apply to
parting line edges or shut-off edges which are required to be sharp.
3.4.3 Surface Finish
Unless otherwise specified on the 2D file, the surface finish shall be as
indicated on SPI finish number 4.
3.4.4 Post Molding Machine Operations (Tolerances)
Refer to Section 3.3 (Machined Parts) for tolerances on post molding
machine operations.
3.4.5 Location of Gates
The location of all gates shall be approved by NT design authority.
3.4.6 Location of Ejectors
The location of all ejectors shall be approved by NT design authority.
3.4.7 Feature Definition
Features include ribs, bosses, holes, counterbores, slots, walls, and so
on. Note that a portion of a wall following a change in curvature or bend
shall be considered a separate feature. The change in curvature is the
separation point between features (see figure below).
NPS51218 Sec.3.4.7
Feature
A
B
C

3.4.8 Fillets and Rounds

Fillets and rounds are intended to be smooth transitions between
adjacent surfaces.

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Issue No 3 NPS51218

3.4.9 Drafts
Drafts shall be defined either by modeling them in the 3D model or by
details in the 2D file.
If no drafts are shown in the 3D model, the primary parting line shall be
specified in the 2D file. Draft shall be applied to the part from the parting
line; the modelled dimension represents the maximum dimension at the
parting line. The wall thickness in the part will be different than the
modelled wall thickness where draft is applied.
Draft always removes material from the model. (STEEL SAFE)

Parting Line

Model

Small end of hole

Parting Line

Part

3.4.9.1 Through Holes

If a through hole is modeled without draft, the modeled dimension
represents the small end of the hole. The small end of a hole shall be
specified on the 2D drawing, or stated to be non-critical.
3.4.10 Flash
There shall be no flash on the part. Minimal flash may be acceptable in
non-critical areas, but must be specifically approved by NT design
authority.
3.4.11 Witness Lines
The location of witness lines shall be approved by NT design authority.

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3.5 Die Cast Parts

3.5.1 Die Cast Parts (Commercial Tolerances)
The 3D model is intended to communicate the design to the supplier.
The information in the model is interpreted using this specification and
the 2D file.

Change information may be provided as an aid to the supplier in

modifying existing tooling / programming to produce the new issue of
the design. If there is conflict between the change information and the
3D model, the 3D model is to take precedence over the change notes.

Except as noted in the previous paragraph, in case of a conflict of

information the order of precedence shall be:

a) 2D file
b) This specification
c) 3D Model
d) American Die Casting Institute, Inc. (ADCI - E12 - 83) E Series
Product Standards for Die Casting.
3.5.2 Die Cast Parts (Tolerances)
Unless otherwise specified on the 2D file or in this specification, parts
shall be manufactured in accordance with the two decimal place
tolerances of the American Die Casting Institute, Inc. (ADCI - E12 - 83)
E Series Product Standards for Die Casting.
Angles ± 1°
Fillets shown in model ± 25% of radius
3.5.2.1 Inside Corners and Edges
Unless otherwise specified on the 2D file, inside corners and edges
shown as sharp shall have a radius of 0.01 to 0.02 inch (imperial) or 0.2
to 0.5 mm (metric).
3.5.2.2 Outside Corners and Edges
Outside corners and edges shown as sharp shall have a maximum radius
of 0.01 inch (imperial) or 0.2 mm (metric). This does not apply to
parting line edges or shut-off edges which are required to be sharp.

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3.5.2.3 Post Casting Machine Tolerances

Machined part tolerances apply to post casting machine operations (refer
to section 3.3 on page 14).
3.5.3 Location of Gates
The location of all gates shall be approved by NT design authority.
3.5.4 Location of Ejectors
The location of all ejectors shall be approved by NT design authority.
3.5.5 Feature Definition
See section 3.4.7 on page 18.
3.5.6 Burrs and Sharp Edges
Remove all burrs, sharp edges and flash.
3.5.7 Fillets and Rounds
See section 3.4.8 on page 18.
3.5.8 Drafts
See section 3.4.9 on page 19.

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4. SYMBOLS
4.1 Weld Symbols
All weld symbols shall be in accordance with NT Corporate Handbook
151.02 (ANSI/AWS Standard A2.4).

5. INCOMPLETE FEATURES
5.1 General
Features not fully detailed in the 3D model shall be detailed in the 2D
file. For example, features such as large arrays of holes may not be
completely modeled. The limits and pitch of the array shall be shown on
the model using a start and stop hole with groups of holes in each corner
indicating pitch. The detail for the rest of the array shall be shown in the
2D file. The limits of the array shall be shown using phantom lines. At
least one formed feature of a pattern shall be part of the model.

6. DATUMS
6.1 General
Three orthogonal planes shall be used, except for flat parts which may
have only two. The datums shall be named A, B, & C. The primary
datum 'A' identifies the first set-up plane for reference measurement (3
point contact) with the secondary 'B' (2 point contact) and tertiary 'C' (1
point contact) providing subsequent alignment and referencing for all
measurements and tolerance variation. Refer to the figure below and
ANSI Y14.5M-1982, Section 4.3.
NPS51218 Sec.6.1
C
DATUM-A
DATUM-C
DATUM-B
A

B B

C A

Note: Datum locations have been chosen for clarity only.

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6.1.1 Single Features

The location of a feature is measured from the datum. Circular features
(except for fillets and rounds) are located by their centers. Other
features are located by the point of the feature closest to the datum,
unless the center is indicated. If the center of a feature is indicated, the
center is used for feature location. The size of a feature is measured
from the feature location point. Fillets and rounds are intended to be
smooth transitions between surfaces.
6.1.2 Groups of Features
Similar features that do not have a "grouping" dimension or explicit
information on the 2D file indicating that they are a group, are to be
treated as individual features.
The location of features in a group is measured from the origin of the
group.
Note 1: If the origin is not indicated, the feature nearest the datum shall be used as
the origin, even if the group straddles the datum. If (c) and (d), below right,
are equidistant from the datum, the origin shall be dimensioned.
Assumed Origin

(c) (d)

3 Places Non Cumulative

A 3 Places Non Cumulative

A

Note 2: If individual features are dimensioned from one of the features in a group,
this feature shall be assumed to be the origin of the group.
Assumed Origin

NPS51218 Sec.6.1.2
NPS51218 Sec.6.1.2

A
A

Note 3: If a dimension string is required, the origin of the group shall be dimensioned.
Origin
NPS51218 Sec.6.1.2

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7. INSPECTION
7.1 Part Verification
The supplier shall ensure that the part meets the requirements (that is,
dimensions, tolerances, material, finish, and so on) of the 2D file,
NPS51218 and the 3D model.
7.2 Specific Requirements
Specific inspection requirements shall be negotiated between the NT
manufacturing location and supplier.
7.3 Part Measurement
The illustration, as per ANSI Y14.5M, shows the orientation of the part
to the measurement planes on the Primary, Secondary, and Tertiary
datum planes (refer to Section 7.1).

Plane A

Establish 3 Point Contact with

Primary Datum Surface A
Plane B

Plane A
90°
Plane C
Establish 2 Point Contact with
Secondary Datum Surface B
Plane B 90°

Plane A
Establish Single Point Contact
with Tertiary Datum Surface C

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Issue No 3 NPS51218

APPENDIX A

Design Guideline
1. Guideline.......................................................................................................26
1.1 Process ..........................................................................................................26
1.2 Language.......................................................................................................26
2. Model Completeness.....................................................................................27
3. Datums..........................................................................................................27
3.1 Datum Selection............................................................................................27
4. Dimensioning................................................................................................28
5. Drawing Notes ..............................................................................................31
6. General..........................................................................................................31
7. Sheet Metal Parts ..........................................................................................33
8. Sheet Metal Assemblies................................................................................33
9. Machined Parts..............................................................................................34
10. Molded Plastic Parts .....................................................................................34
11. Die Cast Parts................................................................................................39

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Issue No 3 NPS51218

APPENDIX A

1. DESIGN GUIDELINE
The following is a guideline for designers to use with NPS51218.
1.1 Process
The specification contains all the generic requirements for parts and
assemblies to minimize the information presented on the 2D portion of the
design file. The specification provides standard tolerances and shall
supplement the 2D file. The designer shall use the following guide to ensure
that the design conforms to both standard practice and any applicable rules in
order to meet supplier needs for consistency and completeness. The
specification and both the 2D and 3D files constitute the total requirements
for fabrication and or assembly. The 3D model controls the dimensions,
while the 2D file and the specification control tolerances and other specific
requirements.
To use NPS51218, the process used to produce the part or assembly shall be
specifically covered by the NPS, and the intended vendors must be capable of
receiving and using the electronic files required by the NPS.
1.2 Language
In this guide, the words "shall", "should" and "may" are to be interpreted as
follows:
Shall: Identifies design requirements which are mandatory
Should: Identifies design requirements which are good practice and
preferred. (Note that violations are subject to the PA review
process.)
May: Identifies design items where the need for compliance is
subject to the PA review process

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Issue No 3 NPS51218

2. MODEL COMPLETENESS
The goal is that the model be complete. The present process has limitations
and it is not always possible nor advisable to put all feature detail in the
model. NPS51218 and this guideline identify the following cases:
Guideline Sections: 6.4 6.8 6.11 7.2 10.1 10.8
10.9 10.10 10.11 10.12 11.1 11.5

NPS Sections: 3.1.3.1 3.2.1 3.3.2.1 3.3.2.2 3.4.2.1 3.4.2.2

3.5.2.1 3.5.2.2 5.1
Where the model is not complete, it is the responsibility of the designer to
ensure that the 2D file clarifies the intent by providing detailed and
dimensioned views or cross-sections.
New situations will be identified during the design process. Agreements
reached prior to PA between design and manufacturing will determine the
content of the 3D file.
Exceptions identified during design reviews should be forwarded to PACE
Product Assurance and Component Engineering, located at Queensview,
Ottawa for review and potential inclusion in the specification and guideline.

3. DATUMS
Datums shall be included in the 2D file for tolerancing and dimensioning. It
is not necessary that the datums match datums in the 3D model.
3.1 Datum Selection
Datums should be selected to reflect design intent and will normally be
associated with features used to assemble the part to another part. For
example:
- mating surfaces or features;
- through or in contact with features that can be used to locate
the part for gauging or measurement;
- planes located by the centers of holes.

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Issue No 3 NPS51218

3.2 In order to provide a reference for tolerance verification measurements, a

datum or set of datums must be identified as follows.
a) Default datums shall be 3 orthogonal planes
b) Visible in the 2D file
c) Primary, secondary, and tertiary datums are specifically identified
as A, B, and C respectively. Points of contact for measurement may
be indicated using standard geometric dimensioning symbols.
d) The names A, B, & C are reserved for primary, secondary, and
tertiary datums. To avoid confusion, these names shall not be used
for other datums without a clarifying note on the 2D file.
3.3 Flat parts may use only 2 datums as a special case.
3.4 Features that are rotated, so that an edge is not parallel to a datum, shall be
dimensioned unless a center is indicated. Features that exactly straddle a
datum shall be dimensioned.
3.5 Datum systems other than those using rectangular coordinates shall be clearly
explained in the 2D file.

4. DIMENSIONING
The following dimensions may appear on all 2D files as a guide to suppliers.
The intent is to indicate important characteristics of a part so as to permit the
supplier and the manufacturing shop to optimize the fabrication process and
part quality.
4.1 Overall height, width, and depth dimensions or reference dimensions shall be
shown.
4.2 All dimensions on the drawing shall show tolerances except reference
dimensions and dimensions within the general tolerances.
4.3 Location and size of features (fastener holes and alignment features) used for
mating a part to another part may be dimensioned.
4.4 Dimensions that are required for further processing, such as jigging for
machining or welding, shall be shown.

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Issue No 3 NPS51218

4.5 Any dimension required for process control maybe marked with an "E" and
the requirements stated in a note.
Example: /<--------------10.01-------------->/
E
Sampling frequency to be agreed between the supplier and NT.
4.6 Aesthetic constraints, flash, untextured flat space for stamping etc., shall be
specified.
4.7 Location and description of marking (e.g., characters or symbols, etc.,) shall
be fully specified.
4.8 Groups of features may need to be dimensioned for proper interpretation.

Note 1: All holes treated as individual features located from datums.

NPS51218 Sec.6.1.2

Note 2: Three of the holes will be treated as individual features located from datums.
There is one group, its origin closest to the datum and dimensioned as
indicated.
Assumed Origin

NPS51218 Sec.6.1.2

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Issue No 3 NPS51218

Note 3: There is only one group. The origin is the feature within the group from
which other features are located.

NPS51218 Sec.6.1.2

Assumed Origin
C

Note 4: There is only one group. A specific string of dimensions is required (more
than one feature within the group is used to locate other features in the
group.) Therefore the origin is dimensioned.

Note 7a: This dimension must be included to avoid ambiguity.

Note 7a

NPS51218 Sec.6.1.2

Origin
C

Note 5: There are two groups, each with an origin defined by group dimensions.

Assumed Origin
C

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Issue No 3 NPS51218

5. DRAWING NOTES (Used as part of the 2D File)

5.1 Must be manufactured in accordance with NPS51218 unless otherwise
specified in this drawing.
5.2 Material:
5.3 Finish:
(Appropriate NT material and finish specifications shall be referenced and the
nominal finish thickness and tolerance stated.)
5.4 All dimensions are in (millimeters) (inches).
5.5 To convert millimeters to inches: 1 mm = 1/25.40 inches
or
To convert inches to millimeters: 1 inch = 25.40 millimeters

6. GENERAL
6.1 Existing NT documentation standards should be followed for assembly
drawings and dimensioning, where applicable.
6.2 No drawing need be fully dimensioned. The designer may elect to fully
dimension.
6.3 All dimensions shall be nominal in the design documentation. Symmetrical
tolerances are preferred but unsymmetrical tolerancing is permitted.
6.4 The intent is that the model be as complete as possible given the limitations
of todays tools and clarity of design intent. For example, for large arrays of
holes, it is permitted to define the limits, pitch, and size without modelling all
the holes. The total number of holes in the array should be specified to reduce
the risk of misinterpretation. Features not complete in the 3D model must be
detailed in the 2D file.
6.5 All parts should be shown in isometric as well as orthogonal views.
6.6 Fastener table and direction of insertion to be shown on the 2D file (see
NPS51218 for examples). Fasteners are permanently attached items,
including clinch and welded fasteners.
Sample Table:
Item Qty Unit CPC Description
10 1 ea P0123456 8-32 Clinch nut

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6.7 When changes to parts are applied, the changes shall be indicated in such a
way that all the items that have changed since the last issue of the files can be
readily identified. The change information will permit the supplier to identify
where tooling changes are required. The change information shall be placed
on the 2D file, or on the Engineering Change (EC) document. Agreement
from the receiving site on where the change notes will go is required. If the
change information is on the Engineering Change document, the receiving
site agrees to provide the change information to the supplier in a form
acceptable to the supplier.
Where a tool or mold for a part does not exist, a note “major change” is
acceptable. In this case, the supplier is expected to process the file as a new
part. Normally a “major change” requires that the part code be changed.
6.8 Radii should be shown in the 3D model.
6.9 Dimensions and tolerances shall be shown for features with dimensions
outside NPS ranges.
6.10 Required tolerances (flatness, perpendicularity, parallelism, etc) not included
in, or different from NPS51218, shall be shown on the 2D file.
6.11 Since the 3D model shows unfinished size (i.e., without plating and or paint)
the designer must ensure that the design meets all assembly fit and function
requirements after finishing.
6.12 The number of decimal places shown in a dimension shall not be used as a
method of defining tolerances. Tolerances which differ from the general
tolerances defined in NPS51218 shall be explicitly shown following each
related dimension.
6.13 Unused.
6.14 After a tool has been built, any deviations from the design intent must be
fully documented by:
a) changing the 3D model and 2D file to match the tooled part; or
b) detailing the deviations from the original design on the 2D file.
The deviations shall be clearly identified as such. The 2D file shall
instruct that future tools are not to include the deviations listed.

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Issue No 3 NPS51218

7. SHEET METAL PARTS

7.1 Direction of punching should be shown on the 2D file where significant to the
design.
7.2 All formed features shall be fully specified in the 2D file. At least one formed
feature of each size and type should be modeled. Formed features are bosses,
lances, dimples, card guides, and so on.
7.3 Sometimes the flatness requirement must be relaxed, due to large numbers of
punched or formed features which might result in unusual, allowable,
distortion of the material. If so, specific requirements must be clearly
indicated in the 2D file.
7.4 Bend radii should be included in the model.
7.5 The location of parts, such as weld studs and nuts that are not located by a
feature in the model, shall be dimensioned on the 2D file.
7.6 Location of bends in sheet metal parts should be dimensioned. (Since bends
are largely a manual fabrication process, this eliminates the need to derive
bend location for shop aid sketches.)
7.7 Where wider tolerances can be acommodated, class B tolerances are
preferred.

8. SHEET METAL ASSEMBLIES

8.1 All required tolerances, including concentricity and parallelism, must be
detailed in the 2D file when they are not covered by NPS51218.
8.2 Dimensions and tolerances for location of parts that are not self-jigging shall
be shown in the 2D file. For example, parts not using tooling pins and
semi-shears, and so on.
8.3 Welding symbols (ANSI) and details shall be shown in the 2D file.
8.4 Tables for threaded holes, as well as holes with special tolerances, shall be
shown.
8.5 Assembling self-fixturing sheet metal parts into an assembly does not always
result in expected assembly tolerances because of distortion during assembly
(example, welding).
If a dimension (tolerance), straightness, squareness, parallelism, and so on, is
important to the design, state the restriction on the 2D file for the assembly.

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Issue No 3 NPS51218

9. MACHINED PARTS
9.1 Tolerances for concentricity and parallelism shall be detailed in the 2D file
where applicable.
9.2 Tables for threaded holes as well as holes with special tolerances, shall be
shown in the 2D file.

10. MOLDED PLASTIC PARTS

10.1 Molded threaded portions not fully modeled shall be detailed in the 2D file.
Internal threads are modeled to the minor diameter, and external threads to
the major diameter.
10.2 The goal is that all features be shown in the model. Features not shown in the
model shall be detailed and dimensioned in the 2D file.
10.3 Finish for cosmetic requirements shall be specified on the 2D file (as per the
list below)
Plastic Texture Paint Match Required
SPI# 1 (optical finish) Yes high gloss
SPI# 4 Yes semi gloss
MT11010 0.001 deep Yes light texture
MT11020 0.0015 deep No
MT11030 0.002 deep Yes medium texture
10.4 Approximate gate location shall be shown, as reference, on the 2D file after
consultation with the mold maker.
10.5 Cosmetic requirements, such as no sink marks, shall be shown on the 2D file.
10.6 The model shall show the features required to accept inserts installed after
molding.
10.7 Include an insert table on the 2D file showing; part #, quantity, and
flush/over/under.

Example:

Flush ± 0.005
Under-flush + 0.000, - 0.010
Over-flush +0.010, - 0.000

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Issue No 3 NPS51218

10.8 Where fit or function impacts occur, draft shall be modelled. For example,
the model shall show draft for situations where sink marks are significant,
where interference with other features/parts is possible, or where draft affects
the function.
Examples of parts that shall show draft:
Potential interference: buttons for a telephone keypad and the recess into
which they fit shall show draft.

Function: Lead-ins on snap-fit features.

Examples of features that should show draft:

Tall ribs, tall screw bosses, tall pins, deep cuts or holes. For an example
of a tall rib, see sketch below.
2.5 mm 1 mm
NPS51218 Sec.7.3 1° Draft Angle

15 mm

Some parts are best constructed by first defining a nominal wall, then
adding protrusions or depression features. Draft shall be modeled in
these cases (see figure below).When a draft is applied to the nominal
wall, the core side of the wall runs parallel to the cavity side, such that
the wall thickness does not vary. The nominal wall draft is modelled to
facilitate communicating the design intent, and to permit checking of fits
with other parts. For example assembling a telephone set.

CORE Parallel
t
t t Nominal wall
t t thickness t
t CAVITY t

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Issue No 3 NPS51218

10.9 For situations not covered by 10.8, there are two ways to represent draft;
modelling or documenting on the 2D file.
If no draft is shown in the model, the designer shall create the model so
that applying the rules of the section 3.4.9 of the specification results in
a part that meets design intent, and indicate draft by one of the
following methods:
a) Dimensioning on the 2D file;
b) Modelling one of a group of features and clearly identifying, on the
2D file, with a cross section or detail, which specific feature of the
group has been drafted. Also indicate that this feature is typical for
the group.
c) Adding a note to the 2D file allowing the supplier to choose the
draft, if neither model or detail is provided.
10.10 If no draft or only a minimum draft is required, it shall be indicated on the
2D file.
10.11 The primary parting line shall be indicated in the 2D file or stated to be non-
critical. If non-critical, the primary mold opening direction shall be indicated.
On complex parts, specifying the parting line may be too restrictive to die
construction with sliding cores or inserts that determine parting lines.
Communication with suppliers and manufacturing is encouraged to address
these datails early and capture them in design files (by modelling or specific
views on 2D files). This issue is addressed before PA sign-off between
design and manufacturing.
10.12 Good practice is to radius inside corners of the part to improve material flow
and to radius outside corners to reduce stress on the mold and improve tool
life. Tool capability and functionality may place some constraints on what
edges may be radiused.
10.13 Refer to SPI Standards and Practices of Plastics Molders (1993 Edition),
commercial tolerances, for industry guidelines.
The designer shall provide, on the 2D file, a simplified table of default
tolerances, reflecting the tolerances described in the SPI guide.
The example tables shown in this section may be used on the piece part
drawing to capture the tolerance information. Default dimensions should be
as specified in the SPI standards. For many parts, tighter tolerances will be

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Issue No 3 NPS51218

required to achieve design intent. Deviations from the standards should be

discussed with and agreed to by the vendor, and input to the tables in place of
the standard values. The designer should be aware of the economic
implications of specifying nonstandard tolerances. The values in the tables
should represent a balance of technical requirements and cost.

The values in the tables are the default tolerances for all part dimensions
unless otherwise specified. In some cases, individual dimensions will require
tighter tolerances than the general tolerances in the tables. These dimensions
should be discussed with and agreed to by the vendor and clearly noted on
the drawing.

The following sample tolerance tables are provided as a template for what
should appear on the part drawing. The values are provided for
ILLUSTRATON ONLY and are specific to a Noryl (General Electric) part.
When using the template on a part drawing, the values appropriate to the part
size, geometry, and material should be substituted.

Linear Dimension Tolerances, as Molded

Dimension Range (in) Tolerance (in)

Relative Location of Surfaces in the Casting 0.0 - 0.999 ±0.0022 per in

Die Cavity 1 - 5.99 ±0.0012 per in
6 - 12 ±0.001 per in
Hole Size 0.0 - 0.125 ±0.001
- Diameter 0.126 - 0.250 ±0.001 ±0.0015
0.251 - 0.500 ±0.002
0.501 - 1
- Depth 0.000 - 0.250 ±0.001
0.251 - 0.500 ±0.005
0.501 - 1.000 ±0.0015
Out of round condition ±0.007in/in of Diam.
Flatness (Note: 1) 0.0 - 2.99 ±0.010
Aditional tolerance for each additional inch. 3-6 ±0.020

Note: 1) Diameter of circle or diagonal of a rectangular surface

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Issue No 3 NPS51218

General Tolerances

Dimension Tolerance (in)

Wall thickness - bottom wall (parallel to parting plane) ±0.001

Side walls (perpendicular to parting plane) ±0.001
Corners, ribs, fillets ±0.005
Draft allowance per side ±2.0 degrees
Concentricity ±0.005 FIM (Full
Indicator Movement)

Note: Wall thickness to be as nearly constant as possible. Any variation should be a

gradual blend

Other Tolerances

Dimension Tolerance (in)

Relative Location of Surfaces in the Cavity
Surfaces in opposite die sections ±0.00x
Surface formed by a moving die member ±0.00x
Allowance for Gate Removal ±0.00x

Parting line Tolerances

Perpendicular to the parting plane ±0.00x
Alignment (Shift) Tolerances ±0.00x

Note: It may be necessary to apply more than one of the above tolerances to a
single dimension.

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Issue No 3 NPS51218

11. Die Cast Parts

11.1 Cast threaded portions not fully modeled shall be detailed in the 2D file.
Internal threads are modeled to the minor diameter and external threads to the
major diameter.
11.2 Finish requirements shall be specified on the 2D file.
11.3 Cosmetic requirements, such as no sink marks, flash, etc., should be shown
on the 2D file.
11.4 The model shall show the features required to accept inserts installed after
casting.
11.5 See Section 10 above for requirements for Model features - 10.2;
Gates - 10.4; Draft - 10.8, 10.9, and 10.10; Parting line - 10.11;
Radii - 10.12.
11.6 For tolerancing see section 10.13 on page 36, replacing the SPI industry
guideline with the American Die Casting Institute, Inc. (ADCI - E12 - 83)
E Series Product Standards for Die Casting.

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