Robert Stout's Website..... rlstout.com
This is still under construction but....
Here in the USA use we have the SAE (formed in 1905), an organization that developed and publishes the specifications needed to standardize the hardware (nuts and bolts) used in the manufacture of goods in the USA… In Europe they have the DIN (formed in 1917), an organization that developed and publishes the specifications needed to standardize the hardware used in the manufacture of goods in Germany. In Japan they have the JIS (formed in 1921), an organization that developed and publishes the specifications needed to standardize the hardware used in the manufacture of goods in Japan. Unfortunately, each of these standards were developed in their respective country and they are not all the same…
In 1947 the ISO (International Organization for Standardization) was formed to create worldwide standards. ..In the past sixty years they have had some success in doing so. Some of the standards developed by the SAE, DIN and JIS have been replaced with ISO standards. Today, if you go into the local hardware store to buy a metric nut, bolt or screw, chances are they will have one.. The hardware sold in most US hardware stores complies with the ISO or DIN standard. Thirty years ago finding any metric hardware in America was difficult.
Now, suppose you are trying to repair, or restore an vintage Japanese motorcycle and you need to replace a few nuts, bolts or screws. The hardware used on that motorcycle was made to the JIS standard that was in effect the year that it was built so, the parts your local hardware store carries may not be the same as the hardware that came on the bike….
For example, the "Phillips screws" used on vintage Japanese motorcycles... (Actually the JIS standard doesn't call them Phillips screws, they are called cross point screws). A 6mm JIS cross point screw will have a have a head that is about 1.5mm smaller in diameter than a similar 6mm ISO Phillips screw… And the screwdriver slot is also made slightly different.... This is why a #3 Phillips screwdriver doesn't fit them very snugly... and using a #3 Phillips to remove or tighten the screw is why you find so many that are rounded out... You be surprised how much tighter an actual JIS #3 cross point screwdriver fits in the slot.
OR a hex bolt with 8 mm threads made to the ISO or DIN standard will have a head that is 13 mm across the flats (uses a 13 mm wrench) but a hex bolt with 8 mm threads made to the JIS standard will have a head that is 12 mm across the flats (uses a 12 mm wrench).
Also, the "standard" pitch is not always the same
either.... For example an 8mm "standard" thread ISO/DIN bolt would
have a thread pitch of 1.25 mm and a 8mm "standard" thread JIS bolt
would have a thread pitch of 1 mm... An 8mm ISO/DIN bolt with a thread pitch of
1 mm would be considered a "fine" thread...