Thread Accuracy Of Zirconium Bolts

The description and units of thread accuracy have clear industry standards. There are differences in the expression methods between different standard systems (metric and imperial). The core unit is based on millimeters (mm), as follows:

The essence of the core unit thread accuracy lies in controlling the dimensional tolerances of the thread (such as deviations in the major diameter, middle diameter, minor diameter), pitch errors, helix angle errors, etc. Its basic unit is millimeters (mm), and in some precise scena -rios, micrometers (μm, 1μm = 0.001mm) are used.

Metric threads (the most commonly used, such as ISO and GB standards) express their accuracy using the combination of "tolerance band code + accuracy grade". The smaller the accuracy grade number, the higher the accuracy.

Tolerance zone code: Composed of letters (with capital and lowercase to distinguish internal and external threads) and numbers, it represents the position of the tolerance zone.

The threads (nuts) are available in these sizes, usually represented by capital letters: G and H. H is the most common and is the standard size.

External threads (bolts / screws, such as zirconium screws) are denoted by lowercase letters: e, f, g, h (h represents the reference position with the smallest deviation).

Accuracy grade: It is indicated by numbers and is divided into 3, 4, 5, 6, 7, 8, and 9 levels.

Levels 3 to 5 represent high precision, suitable for applications in precision instruments, aerospace, and other fields.

Grade 6 represents the general precision level, which is commonly used for industrial fasteners (such as zirconium screws), and is denoted as 6g or 6H.

Levels 7 to 9 are of low precision and are suitable for scenarios where the assembly requirements are not very high.