These postings from Barton-Chapple's "Television For The Amateur Constructor" (Pitman's, London, 1933) were designed for the following size and configuration of aluminium scanning disc:
Thickness of aluminium disc = 32 S.W.G. = 0.0108 inches = 0.2734 mm (this is substantially thinner than the present NBTVA club discs!)
Diameter = 20 inch = 51 cm (substantially bigger than most club discs).
Number of lines/apertures = 30, each 0.028 inches = 0.7 cm square, punched to provide square shape.
Picture aspect ratio: 3 horizontal: 7 vertical, vertical scan lines.
Picture repetition rate = 12.5 pictures per second, no interlace.
I am reproducing the following chapters on this initial posting:
Chapter 2: "A [Mechanical Television] Workshop In The Home" pps 36 to 47.
Chapter 9: "Building Television Apparatus [from Baird Junior Kit]" pps. 167 to 177.
Chapter 10: "Bulding Television Apparatus [making all parts]" pps 178 to 211.