Like it or not, metric fastners are here and becoming more prevalent in the manufacture of many products, particularly automotive.

Knowing a few basics about what types of metric fasteners are in use can save you time, money and lots of aggravation.

There are two basic metric styles DIN European and JIC Japanese. The difference between the two styles is very significant.

European style are most commonly available from industrial suppliers on the net and in brick and mortar stores. The sizes most typically offered in most DIN assortments range from 6mm to 24mm in diameter with  course thread pitches 1.00, 1.25, 1.50, 1.75, 2.00, 2.50, 3.00.

Japanese style are a little harder to find. The JIC metrics use one thread pitch (1.25) for several different diameters 8, 10,12. European change the the thread pitches on 10 and 12 mm diameters.

Another difference in the two styles is head size of the bolt. Because of the limited space in the engine compartments of Japanese vehicles and the need to reduce weight, engineers needed a more compact fastener. So they created a smaller head screw. A common name used for this style of metric bolt is "Japanese Small Head Cap Screws". The Japanese manufactures also use DIN style so both styles are needed.

If you are servicing Japanese autos, trucks, tractors and small engines it would be good to start with an assortment of JIC and then fill in your metric assortment with DIN European to have a complete selection.

American and European auto manufacturers are using more metrics everyday. They use DIN almost exclusively. But there is no guarantee, they may for cost or supply reasons at any time throw in another style without much fanfare.

Generally speaking a simple 6mm to 14mm assortment will provide a good resource...open the hood of a Japanese vehicle and you need both JIC and DIN to do the job correctly.