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BS 4978:1988

Superseded
Superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

View Superseded by
superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

Specification for softwood grades for structural use
Available format(s)

Hardcopy , PDF

Superseded date

15-08-1996

Language(s)

English

Published date

30-11-1988

Foreword
Committees responsible
Specification
0. Introduction
1. Scope
2. Definitions
3. Stress graded timber
Section two. Visual stress grading
4. Measurement of characteristics
5. Grade requirements
6. Marking
7. Re-marking
Section three. Visual stress grades for laminating
8. Requirements for laminating grades
Section four. Machine stress grading
9. Requirements for machine grading
10. Marking
11. Re-marking
Section five. The acceptance of stress grading machines
12. General
13. Requirements for all systems
14. Additional requirements for 'machine controlled'
    systems
15. Additional requirements for 'output controlled'
    systems
Appendices
A. Determination of the knot area ratio in cases of
    dispute
B. The control and supervision of stress grading
    operations
C. Determination of slope of grain
D. Species marking
E. Determination of settings for grading machines in
    'machine controlled' systems
F. Determination of settings for grading machines in
    'output controlled' systems
G. Testing for quality control of grading in 'output
    controlled' systems
Tables
1. Permissible limits for the SS and GS visual stress
    grades
2. Visual requirements for machine grades
3. Values of species constants
Figures
1. Edge, face and margin areas
2. Knot projection
3. Typical knot area ratios and the resulting grades
4. Measurement of rate of growth
5. Amounts of wane
6. Fissures
7. Measurement of bow, spring, twist and cup
8. Swivel handled scribe for determination of slope of
    grain
9. Use of scribe
10. Measurement of slope of grain
11. A graph of variables A and B for use in the
    determination of cusum control constants for mean
    modulus of elasticity
12. Cusum control form (in control)
13. Cusum control form (out of control)
14. Cusum chart of data from figures 12 and 13

Specifies 2 methods of grading softwood namely, visual and machine stress grading. Permissible limits of characteristics for: (a) 2 visual stress grades - General Structural (GS) and Special Structural (SS); (b) 3 laminating grades - LA, LB and LC. Requirements for machine stress grades; Machine General Structural (MGS), Machine Special Structural (MSS), M50 and M75 and Strength Classes are specified. Also includes performance requirements for machines which grade softwood.

Committee
B/518
DevelopmentNote
BS DRAFT 93/104870 DC REFERS TO AMD 3
DocumentType
Standard
Pages
48
PublisherName
British Standards Institution
Status
Superseded
SupersededBy
Supersedes

Standards Relationship
ISO 2299:1973 Similar to
ISO 2301:1973 Similar to
ISO 1030:1975 Similar to
ISO 2300:1973 Similar to

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