Bolt Size Chart report

Bolts are one of the most indispensable parts of hardware. We can see or use bolts in many places in daily life. But there are different types and sizes of bolts, and their uses also differ. Do you know how to check the bolt size? However, the surface of most bolts has not been marked with a model number.

Bolts are externally threaded fasteners used with a nut. It will not rotate in the assembly process but is tightened by turning the nut. Nuts and bolts are essential fastenings, critical in the safe assembly of machinery, equipment, furniture, and much more. The right bolt size must be used in most circumstances.

If you are searching for more details about bolt sizes, please continue reading the following articles. This article will provide a complete guide of bolts, which involves bolts definition, dimensions, and the standard bolt sizes chart in metric and imperial.

Bolt Size Guide

Metric nuts and bolts are commonly referenced using 'M' sizes: M3, M8, M12. But the size of a metric fastener is more accurately specified using the diameter, pitch, and length dimensions in millimeters. For nut size, the measurements used are simply diameter and pitch.

For example， metric bolt specification: M8-1.0 x 20.

• The letter ‘M’ indicates that this bolt uses a metric thread.
• The number '8' refers to the nominal diameter of the bolt shaft in millimeters.
• The number 1.0 is the thread pitch of the bolt, which is the distance between threads in millimeters.
• And the final figure, 20, is the length in millimeters.

Nominal Bolt Size

The diameter is equal to the external diameter of the threads. The bolt diameter is a little smaller, and the nut diameter slightly larger. But it is easier to specify the components by a single size designation since the bolt and nut are mating components.

Thread Pitch

Pitch is the distance from the crest of one thread to the next or the distance from one thread groove to the next. It is also described as the number of threads per inch.

Length

The length of a metric bolt is measured in the same way as imperial, inch-based bolts and fasteners. Socket head, pan head, button head, and hex head bolts are measured from the underside of the bolt head to the end of the shaft. For flat head bolts, the length includes the bolt head height, and for dome head bolts, the length is measured from the thickest, highest point on the curved head.

Bolt Size Charts

Coarse threads are with a larger pitch, and fine threads are with a smaller pitch. The following metric stud bolt size table is meant to help determine the correct size bolt or nut for your purpose. The bolt size charts provide coarse and fine thread sizes in both US and metric sizes.

Coarse Thread Bolts

Fine Thread Bolts

Metric Bolt Dimensions Chart

Check out the standard bolts size chart in metric or imperial below.

Imperial Bolt Dimensions Chart

Hole Sizes for Metric Bolts

The defined diameter of metric bolts is slightly larger than the actual diameter of the bolt shaft. So an M8 bolt would have a shaft diameter that’s a little under 8mm, which means that the bolt should fit through an 8mm hole. The following table provides examples of clearance hole sizes, standard or coarse thread pitches, along fine thread pitches and their corresponding tapping hole sizes.

In the above brief guide, we introduce the standard bolt size charts, which will hopefully help dispel any confusion.