Early JIS screw size differences (1 Viewer)

[Krondor]

I had the hardest time finding a correct screw size for the early wiper and light rotary switches. Turns out I wasn't crazy. The correct thread is an M3-0.6! Here is a little history.

So if you have an early cruiser and can't get the screw to thread in. You are not crazy. The threads are different.


In April 1967 the JIS (Japanese Industrial Standard) was changed to match the screw pitches of the ISO standard.
A little chart is below comparing pre April 1967 JIS screw pitches with post April 1967 JIS screw pitches.
It may help explain why some metric screws don't seem to fit on your motorcycle or car.

Pre Apr 1967 JIS
3mm.....0.6
4mm.....0.75
5mm.....0.9
6mm….. 1.0
8mm.....1.00
10mm...1.25
12mm...1.5

Post Apr 1967 ISO
3mm.....0.5
4mm.....0.7
5mm.....0.8
6mm… ..1.0
8mm.....1.25
10mm...1.5
12mm...1.25

Machine Screws - Pan Head - Metric - JIS Zinc Pre ISO Coarse Pitch - Classic Fasteners

www.classicfasteners.com.au