ISO Metric Thread Chart

ISO metric threads are an internationally recognized standard thread featuring a symmetrical 60° thread profile angle, with dimensions expressed in millimeters (mm). ISO metric threads are widely utilized in various fasteners; they constitute the most widely adopted universal thread type and represent one of the earliest international standards to be established by consensus.

The standards related to metric thread tables are ISO 68-1, ISO 261, ISO  262, and ISO 724. ISO 261 and ISO 262 provide standard diameter-pitch combinations, which are suitable for design selection. ISO68-1 specifies the geometric characteristics of the basic tooth profile of metric threads. ISO 724 provides calculation formulas for basic thread dimensions, which can provide technical guidance for thread design and proofreading.

According to the definition of ISO 68-1, the thread design is characterized by Major Diameter and Pitch. The flank angle of the metric thread is 60°, that is, the angle between the two sides of the thread and the thread axis is 60°, which is structurally stable and conducive to force transmission.

Metric Thread Marking Symbol

The information expressed by the thread marking symbol is the standard system, nominal diameter, and pitch, in millimeters, which are the core parameters when selecting, processing or purchasing threaded parts. For example, M6×0.75 means a metric fine thread with a Major Diameter of 6mm and a Pitch of 0.75 mm. When there is no Pitch, M6 means a coarse thread with a Major Diameter of 6 mm.

Terms Used In Thread Specifications

The various parameters in the thread specifications do not exist independently and can be derived through related parameters. This conversion method is very important in thread design and detection, which can help us quickly determine the key dimensions of the thread and ensure assembly accuracy and strength requirements.

The conversion formula between Fundamental Triangle Height H and Pitch P is as follows:

The Minor Diameter and the Pitch Diameter can be calculated by combining the known major diameter with the Pitch. The Minor Diameter D1 and Effective Pitch Diameter D2 are calculated by the Major Diameter D as follows:

The following chart shows the standard specifications of ISO metric threads. According to your needs, you can choose the appropriate thread specifications for processing. We provide one-stop internal and external thread processing services.

Custom CNC Machining Product Case

01

Custom CNC Machining Aluminum Alloy Liquid Cooling Plate

02

CNC Turning Stainless Steel Hydraulic Quick Coupling

03

Custom CNC Machining Copper & Aluminum Heat Sink Fin

04

Precision Automatic Lathe Parts

Metric Threads - Coarser Threads(M1-M68)

The coarse thread has a wider distance between teeth, is more resistant to damage, and has a loose processing tolerance, making it suitable for outdoor use.

Metric Threads - Fine Pitch(M1-M28)

Fine threads have a smaller pitch and stronger locking ability, making them more suitable for high-vibration scenarios. Under the same conditions, fine threads have more turns, more evenly distribute the tension, and can bear greater loads.

Labeling Examples

I believe that through the previous explanation, you have already understood the basic knowledge of the ISO Metric Thread Chart. Below is a simple example to help you test whether you have learned how to read the parameters of metric threads.

• M5 x 0.5: This indicates a fine thread with a diameter of 5 mm and a pitch size of 0.5 mm.
• M10: This refers to a metric coarse thread with a diameter of 10 mm (which, with reference to the standard thread table, corresponds to a pitch size of 1.5 mm).

Conclusion

ISO Metric Threads provide the essential geometric data for CNC machining by defining precise pitch and diameter standards. Strict adherence to these standards allows for predictable quality control and seamless assembly in the international supply chain.

LVMA CNC offers professional CNC machining services, ensuring these stringent ISO thread specifications are met with professional precision. Get a free quote within 24 hours if your parts are ready.