The basic definition of the accuracy grade of screw and guide rail is vague, which generally means to reflect the different differences between the positioning surface of linear guide rail and datum plane, or the repeated positioning accuracy of lead screw under the condition of different matching clearance of rolling element and related components. If you can understand the role of ball screw in servo system and linear guide rail in precision guiding elements, the concept of "precision level" is not difficult to understand. To put it bluntly, high-precision screw can be used in high-precision equipment. Of course, high-precision screw price is not cheap.

于這些指標，廠家有專門的測試設備給出結果，反映在我們這些客戶眼中呢，我們只需要關心產品樣本中寫的行業內通用的標識即可。這些標識有的不同廠家叫法還可能不同。比如有的叫“普通級”，有的叫“一般級”，這樣不同的叫法只是相對于自己廠家的“精密級”而言的，為了對比不同廠家之間的產品，我們好還是看那些術語吧。

As for these indicators, the manufacturer has special test equipment to give the results, which are reflected in the eyes of our customers. We only need to care about the general marks in the industry written in the product samples. Some of these marks may be called differently by different manufacturers. For example, some are called "ordinary level" and some are called "general level". Such different names are only relative to the "precision level" of their own manufacturers. In order to compare the products of different manufacturers, we'd better look at those terms.

比如滾珠絲杠，有個“e300”和“e2π”這是行業通用的參數，下面地址是個pdf頁面，有說明，但是他用的是“v300”和“v2π”是一樣的。

For example, the ball screw has "E300" and "E2 π", which are common parameters in the industry. The following address is a PDF page with instructions, but it uses "V300" and "V2 π", which are the same.