BS 4145:1967

Co-operating organizations
Foreword
Specification
1 Scope
2 Definitions
3 Classification
4 Finish
5 Flatness
6 Thickness
7 Electric strength proof test in oil
8 Surface electric strength proof test in air
9 Insulation resistance
10 Carbon arc test
11 Spirit burner test
12 Water absorption
13 Deformation under compression
14 Shear strength
15 Cross-breaking strength
Appendices
A Conditioning of test pieces
B Electric strength proof test in oil
C Surface electric strength proof test in air
D Insulation resistance
E Carbon arc test
F Spirit burner test
G Water absorption
H Deformation under compression
J Shear strength
K Cross-breaking strength
Figures
1 Electrode arrangement for electric strength test
2 Apparatus for carbon arc test
3 Circuit diagram for carbon arc test
4 Spirit burner
5 Arrangement of test piece for spirit burner test
6 Assembly of punch, die and bolster for shear
    strength test

Requirements for two types of board for electrical purposes made from glass bonded mica powder, from ⅛ in (3.2 mm) up to ½ in (12.7 mm) in thickness. Definitions, classifications, finish, flatness, thickness, electric strength proof test in oil, surface electric strength proof test in air, insulation resistance, carbon arc test, spirit burner test, water absorption, deformation under compression, shear strength and cross breaking strength. Methods of test given in appendices.

This British Standard specifies requirements for boards for electrical purposes, made from glass bonded mica powder, from ⅛ in (3.2 mm) up to ½ in (12.7 mm) in thickness.

NOTE Although limits are given only for boards up to ½ in (12.7 mm) thick, boards are made in greater thicknesses up to 1½ in (38.1 mm). For boards over ½ in (12.7 mm) thick, limits and test methods should be agreed between the purchaser and the supplier.

Two types of board are covered, both of which are incombustible.

The boards have good resistance to arcing, good mechanical properties and can be machined provided suitable techniques are employed. The boards are suitable for use as arc shields, terminal boards and high temperature panels.

The density of the boards covered by this standard may be taken as approximately 0.09 lb/in³ (2.5 g/cm³). Density is not, however, a guide to the quality of the board.