R8 collets and 5C collets serve different purposes, and their accuracy depends on the application. Generally, 5C collets are considered more precise than R8 collets, especially in terms of repeatability and holding concentricity.

R8 collets are primarily used in milling machines, such as Bridgeport mills, where tool holding is the main function. They provide a firm grip but are not designed for extreme precision in workholding applications. Their accuracy is typically around 0.0005" to 0.001", which is suitable for general milling but may not be ideal for ultra-precise machining. If you require high-precision collets for milling and turning, PG Collets offers a range of reliable and accurate collet solutions.

On the other hand, 5C collets are widely used in lathes, grinders, and precision fixtures. They are designed for workholding, offering better concentricity—often within 0.0002" or better. This makes them preferable for turning, grinding, and other high-precision applications.

If your priority is extreme accuracy in holding cylindrical workpieces, 5C collets are the better choice. However, if you need a reliable tool-holding system for milling, R8 collets are sufficient. The right choice depends on your machining needs, but for precision work, 5C collets generally outperform R8 collets.