How do you specify metric threads?

Asked by: Sarah Campanita

Designation. A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (the maximum thread diameter) and the pitch P, both expressed in millimetres and separated by the multiplication sign, × (e.g., M8×1.25).

How are threads specified on metric bolts?

Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimetres (measured along the length of the fastener). For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm.

What are standard metric threads?

Standard metric screw threads are designated by pitch in millimeters (mm). This is the distance measured between the peaks of two adjacent threads. ASTM fastener standards measure threads by TPI: threads per inch. You literally just count the number of threads that cover a one-inch distance.

Does M10 mean 10mm?

Steel bolt with M10 metric thread. Metric threads are designated with a capital M plus an indication to their nominal outer diameter and their pitch: This bolt is M10 x 1.5 – which means the outside diameter is 10mm and the threads are 1.5mm apart (the most common thread pitch for M10).

How do I know if I have a M6 or M8 bolt?

The defined diameter of metric bolts is actually slightly larger than the actual diameter of the bolt shaft. So an M8 bolt would have a shaft diameter that’s slightly under 8mm which means that the bolt should fit through an 8mm hole.

What does M8 1.25 mean?

For metric fasteners, you will see a M8 x 1.25 or an M8 x 1. For thread pitch, the distance between two points is the second number meaning the higher the number the fewer threads there are. This means the M8 x 1.25 is the coarse threading and the M8 x 1 is the fine thread.

Are standard and metric threads the same?

Metric thread pitch measurements are read differently than standard ones. While for standard thread pitch measurements the lower number is coarse thread and the higher number refers to fine thread, in metric this is opposite. M10-1.50 is a coarse thread denotation while M10-1.25 is a fine pitch.

What are the different types of metric threads?

BSPP (BSP, parallel) BSPT (BSP, tapered) metric parallel. metric tapered.

How do I determine thread size?

Use a caliper to measure the nominal male or female thread press to crest diameter on the first fourth.

How do you read thread size?

Thread sizes are given in nominal sizes, not in the actual measurement. The exact measurement is slightly below the named or nominal size. For example, a 6mm bolt may measure 5.8mm or 5.9mm, but it is called 6mm bolt. It is also common to use “M” before the bolt size, such as M6 for a 6mm bolt.

How do I know if my nut is metric or standard?

Metric fasteners are measured by length and pitch, or the distance between threads. So the systems are opposite in a way: The higher the TPI in a standard bolt, the finer the threads because there’s more squeezed into a set space. The greater the pitch on metric fasteners, the more distance between threads.

How do I know if my threads are metric or imperial?

Metric threads are measured by their pitch. That is the distance from the crest of one thread to the crest of the next measured in millimetres. The pitch of a metric thread can be checked by direct measurement with a metric rule. Imperial threads have their pitch measured indirectly as a given number of teeth per inch.

Do metric bolts have different threads?

Metric thread callouts are fundamentally different because the thread pitch (distance between each thread, in mm) is specified instead of threads per inch or per mm. For example, an M10x1. 5 (coarse) thread has a 1.5mm pitch, while an M10x1. 25 (fine) thread has a 1.25mm pitch.