BS 4978:1988
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
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Specification for softwood grades for structural use
Hardcopy , PDF
15-08-1996
English
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
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