Metric Fasteners Many issues still surround the use of the Metric System in manufacturing today. In the 70's there was an effort to increase the use of the metric system in the United States. Congress passed the Metric Conversion Act of 1975, then the Omnibus Trade and Competitiveness Act in 1988, making the metric system the preferred method. Today the US still does not consider the metric system as its primary or preferred means of measurement. Looking more specifically at the manufacturing of fasteners, screw, and bolts metric fasteners are in a large part driven by the Automotive Industry. Let's start with design and engineering. In the 70's many companies were still on draft boards, however today we fully utilize CAD systems which not only let us draw parts to size instead of scale, they easily switch between the english and metric systems of measurement. However specifications are still hard to get in metric, Why is there not a IFI standard for metric hex washer head when one is available in inches?

The shop floor and manufacturing process is full of more English measurement potholes. Converting to inches shaves 10ths off of tolerances by rounding. Lathes, mills, grinders, and other tool making equipment and support equipment have dial indicators and measurement scales all based on the english system. All gauging equipment and tools such as sliding calipers, micrometers, and test equipment like torque wrenches use of the English measurement system and have to be replaced with their metric system equivalents.

Duplication creates waste such as tools for production where most companies have metric and english drill bits, taps, roll thread dies, etc... Along with dual head markings for inch-grade and metric-property class. This duplication along with the efforts for conversion between the two systems adds up to a tremendous amount of waste.

Office systems and subcontracting of services for manufacturing operations, heat treating, plating, etc... need to be analyzed. Not only from an engineering drawing stand point of linear measurement, volume, and weight but production control, purchasing, and accounting systems use of weight and piece tracking. With all the underling systems and measurement tools it's easy to see why changing from English measurement to the metric system will take a long time and cost us all a lot of money in the process.

By Patrick Winter
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