BS 5204-1:1975

Cooperating organizations
Foreword
Specification
1. Scope
2. References
3. Nomenclature
4. Material
5. Lengths of straightedges
6. General features
7. Finish
8. Flatness of working surfaces
9. Equality of depths
10. Flatness of side faces
11. Squareness of working surface and side faces
12. Marking
13. Protection against climatic conditions
14. Case
Appendices
A. Minimum general dimensions for straightedges
B. Recommended methods of testing cast iron
    straightedges
C. Recommended chemical compositions of plain and
    alloy cast irons and method of heat treatment
Tables
1. Tolerances on flatness of working surfaces
2. Tolerances on equality of depth between working
    surface and faces of support feet (bow shaped):
    tolerances on uniformity of depth between working
    surfaces (I-section)
3. Minimum general dimensions for bow shaped straight-
    edges
4. Minimum general dimensions for I-section straight-
    edges
Figures
1. Bow shaped straightedge
2. I-section straightedge
3. Exaggerated illustration of squareness deviation
4. Alternative positions
5. Design of supporting feet
6. Alternative methods of using parallel blocks to
    support the straightedge in position (b) of figure 4
7. Test by inclination method
8. Plotting of readings

Metric sizes in lengths up to 8000 mm bow shaped and 5000 mm I section. Two grades of accuracy for each type, material, manufacture, design. Recommended dimensions and test methods appended.

This Part of this British Standard specifies requirements for cast iron straightedges of bow shaped design and of I-section in metric sizes. Two grades of accuracy are provided for each type, namely grade A and grade B.

Requirements applicable to both types are given in clauses 3 and 4 and 7 to 14 inclusive while clauses 5 and 6 specify particular requirements relating to bow shaped straightedges in lengths up to and including 8 000 mm and I-section straightedges in lengths up to and including 5 000 mm.

Recommended general dimensions, methods of testing and heat treatments are given in appendices.

NOTE A straightedge complying fully with the requirements of a superseded standard continues to be operational but it should be brought into full association with this standard when convenient, i.e. when the surfaces are reconditioned and/or retested.