Red Seal Machinist Practice Exam 2025 – All-in-One Comprehensive Guide to Exam Success!

The Imperial system, which uses inches as its primary unit of measurement, is the most commonly used system in machining in North America. This preference is deeply rooted in tradition, as American manufacturing has historically adopted the Imperial system for its precision measurement tools, machining standards, and general practices.

Machinists typically use fractional inches for measurements of tools, parts, and components, which are easily understood and applied in the context of fabrication and assembly. The familiarity of the workforce with this measurement system also supports its continued use, as machinists learn to read and interpret measurement tools like calipers and micrometers calibrated in inches.

While the Metric system is also recognized and utilized—especially in some areas of engineering and science—the Imperial system remains predominant in many machine shops and manufacturing settings across the United States and Canada. Mixing systems could lead to confusion and errors in production, which is why the Imperial system continues to be the standard in many applications within the industry.