ISO Metric Screw Thread Tolerances

ISO Metric Screw Thread Tolerances are important for making sure your products meet international quality standards. In this article, we’ll explain what ISO Metric Screw Thread Tolerances are, and how they can help you ensure that your products meet the highest possible standards.

What is a Metric Screw Thread?

ISO metric screw threads are the most common type of screws in the world. They have a pitch (distance between threads) of 1/10 mm, 1/5 mm, 1/2 mm and 3/4 mm. The smaller the pitch, the finer the screw will be. ISO metric screw threads are also known as BSW or ISO 6789 screw threads. metric screw size chart

Metric Screw Thread Tolerances

ISO standards specify thread tolerances for screws and other fasteners. The most common tolerance is the “plus-or-minus” (±) 3° pitch, but ISO also specifies a number of other pitch tolerances.

Thread tolerances are important because they ensure that screws fit properly into their mating parts. If the screw’s threads aren’t tolerant enough, it can strip the threads in the mating part. This can cause the part to fail catastrophically.

The ISO standard for thread tolerances is ISO 10303-3:2010. It specifies six types of tolerance: plus-or-minus 0.5°, ±1°, ±2°, ±3°, ±4°, and ±5°. In addition to pitch tolerance, ISO 10303-3 also specifies thread form, taper angle (the degree at which the screw’s diameter decreases as its length increases), and yoke size (the distance between the center of the screw’s head and its yoke).

What is the ISO metric screw thread standard?

The ISO metric screw thread standard is a technical standard for the dimensions and tolerances of screws. It was developed in the early 1960s and has been revised multiple times since then. The latest version, ISO 11936-4, was published in 2013.

The ISO metric screw thread standard defines six types of screws: straight screw, slotted screw, Phillips head screw, self-tapping screw, tapped hole screw, and captive bolt screw. It also defines the dimensions and tolerances for each type of screw. For example, the straight screw has a diameter of 12 mm and must have a tolerance of 0.5 mm.

The ISO metric screw thread standard is important because it allows manufacturers to produce screws with consistent dimensions and tolerances. This prevents problems like mismatched parts that can cause defects or failures.

Why does a metric screw thread need to be standardized?

There are a number of reasons why a metric screw thread needs to be standardized. First, it allows for a consistent interchangeability between screws made in different countries. Second, it ensures that all screws have the same length and diameter so that they can be fitted together precisely. Third, it eliminates the need for special tools to tighten or loosen screws – simply use the appropriate size screwdriver. Fourth, it makes it easier to measure the torque required to secure screws in place. Finally, by standardizing screw threads, manufacturers can create more compact and lightweight products without sacrificing strength or stability.

Metric Screw Threads in other Standards

ISO metric screw threads are commonly used in other standards, including American National Standard for Electrical Wire Connectors (ANSI/NFPA 61), British Standards BS EN 883:2008 (formerly DIN 883), and Japanese Industrial Standards JIS Z8609. ISO metric screw threads have pitch sizes that are multiples of 10 millimeters, with a pitch size of 20 millimeters being most common. The ISO metric screw thread tolerance range is +0.20 to −0.40 mm.


If you’re working with ISO Metric screw threads, it’s important to be aware of the tolerances that are in place. Not all hardware stores carry the correct screws and bolts, so it’s important to know what those tolerances are in order to ensure a proper fit. This information can also come in handy when ordering parts online or from other sources. Read More