One problem with standardizing the metric system is the initiative to fully convert metric specifications to an ISO standard. Although the process has begun, most industries are unenthusiastic about converting from DIN or metric ANSI.
|Product Type||Metric Specification||Scope|
|960||8765||Partially Threaded (Fine)|
|961||8676||Partially Threaded (Fine)|
|Hex Nuts||934||4032||B220.127.116.11M (style 1)||Classes 6, 8, & 10|
For example, metric hex cap screws are generally manufactured to one of the three standards:
- DIN 931 (DIN 933 fully-threaded)
- ISO 4014 (ISO 4017 fully-threaded)
- ANSI/ASME B18.104.22.168M
Although the various standards may have different dimensional properties, products made to these three standards are interchangeable. Hex cap screws manufactured to the dimensional specifications of any one of the listed standards are compatible with nuts manufactured to the metric specification of any of the respective organizations. The main difference between each of the hex cap screw standards is the width across the flats dimensions for the M10, M12, and M14.
Each metric standard is product specific. For example DIN 931 is for partially threaded coarse thread metric hex cap screws. DIN 960 is the specification for partially threaded fine thread metric hex cap screws. The specification used to produce the corresponding inch series fastener is ANSI B 18.2.1. However, the ANSI B 18.2.1 specification encompasses eight product types under the broad heading of "Square and Hex Bolts and Screws." Therefore, one must state the pattern of the desired product; in this case, hex cap screw. Under the metric system, each of the eight product types would have its own individual standard.