Metrication at Caterpillar Tractor
From the July/August 2007 issue of USMA’s Metric Today.
by Don Hillger
Caterpillar Tractor Company began to metricate its US plants in 1971, shortly after publication of the US Metric Study—A Metric America: A Decision Whose Time Has Come—that had been commissioned by Congress. As a multinational operation, Caterpillar was convinced that going metric was in its best interest. With plants in many countries, it was already involved in the expensive task of converting inch drawings from the US to metric for non-US operations. The company’s chief standards engineer summed up the decision:
The longer we wait to go (metric), the more costly and difficult it will be.
To make all new designs with dimensions in millimeters, coordination among departments within Caterpillar was important. However, Caterpillar decided not to force its suppliers to go metric. The company developed a computer program to convert dimensions for suppliers requiring inch measurements, giving suppliers time to adjust. Although some were initially surprised at Caterpillar’s conversion, suppliers have since converted to metric.
Training was needed, especially for design engineers, and generally consisted of a two-hour session. The net cost of this training was effectively zero, because overseas engineers were no longer going through the costly conversion of inch designs.
Caterpillar is a strong advocate of metric education. The company’s employment application forms query applicants on their knowledge of the metric system, and Caterpillar’s major presence in Peoria, Illinois, led the city’s school district to teach the metric system almost exclusively.
Actual costs for going metric were much lower than the initial cost estimates because Caterpillar did not have to replace tools, gauges, and measuring equipment. In addition, plant disruptions were almost non-existent. Dual dimensioning allowed the use of existing designs and equipment. Step by step, soft conversion of old designs progressed to hard conversion as new products were introduced. Over time, the attrition of non-metric designs created a predominantly metric operation.
Caterpillar found that adopting metric sizes for steel, particularly sheet and plate steel, reduced inventory and costs. A 54% saving was achieved by replacing 74 non-metric sheet and plate steel sizes by 34 metric sizes. Over 500 flat bar sizes were replaced by fewer than 200 metric sizes. Most of these changes took place over a three-year period, with surprisingly few exceptions.
Caterpillar chose metric drill sizes already used in Europe, because they provided a better choice of drill sizes and thread choices in some sizes. This change did not increase costs. However, Caterpillar continues to use some ISO inch fasteners for its US operations.
One aspect of Caterpillar’s metrication was its aim at influencing international standards. This was accomplished by working with the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) to provide American input to the standards-making process.
The benefits of metric conversion at Caterpillar included elimination of redesign in overseas plants; reduction in the number of sizes, resulting in fewer and larger steel orders, as well are reduced steel inventory; improved design selection resulting from a more logical sequence of sizes; and cost reductions of between $900 000 and $1 000 000 a year!
In summary, Caterpillar realized that the cost of conversion was minimal and would not have been lower had they put it off until later. The company feels that its customers and users have likewise reaped benefits from its gains in going metric. In the end, Caterpillar achieved the goals of making its products more salable worldwide, improving standardization and design, and reducing its production costs.
Note: Material for this article came from various articles about Caterpillar’s conversion to metric.