This useful chart shows imperial and metric equivalents, as well as offering suggested tapping drill sizes for a wide range of threads.

Download links:

ChartA

ChartB

ChartC

Many thanks to the 'Man Who Can Scan' - Nick Farr - for sending us good quality scans of his copy (we don't have an electronic version on file). Nick offers the following advice:

Charts A and B are the full chart in two sheets of the same size in portrait which ideally would best be printed onto A3+ paper, which would give a chart the same size as the original, that could be made by trimming and sticking them together. Chart C is a landscape of the full chart which could be printed out on an A2 or larger printer, to give a one piece size of the original. I can't say the sizes would be exact, but they should be close, I have printed all three on A3 paper, but of course they are smaller but the landscape one is still a readable size for close reading.

The charts are also easily read as PDFs by zooming in and may be usable printed onto two A4 sheets if you have good enough eyesight!