# What do the dimensions on a bolt mean?

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The size of a metric bolt is specified using pitch, diameter, and length in millimeters. For example, in M8-1.0*20, the “M” means the Metric thread designation, the digit 8 refers to the Nominal diameter (in millimeters), 1.0 refers to the pitch, and 20 refers to the length.

## What do the numbers mean on bolts?

The first number in each size is the nominal or root (minor) diameter (mm) and the second number is the thread pitch (mm). NOTE: Remember that the nominal bolt diameter is the measurement of the bolt diameter as taken from the bottom of the threads NOT the top (which would be major diameter).

## What size bolt should I use?

A typical rule of thumb . . . Use a bolt diameter that is 1.5 – 2.5 times (up to three times) the thickness of the thinner material you are bolting together. So, for 1/8″ material, a 1/4″ diameter is often a good bolt choice. For 1/4″ thick material, perhaps a 3/8″ or 1/2″ bolt.

## What does M12 mean?

6. Those are metric screw dimensions. M10 means a 10 millimeter outer diameter for the bolt or whatever piece it is; M12 means 12 millimeters. The part after the ‘x’ is the pitch — how many mm a thread is wide. To figure out which you have, you can measure the existing part with calipers and a thread gauge.

## What does 8.8 on a bolt mean?

A property class (PC) is the metric equivalent of a grade in inch series terminology. … So, in English, a PC 8.8 bolt is a bolt with a nominal tensile strength of 800 MPa and a nominal yield strength that is 80% of the bolt’s nominal tensile strength, or 640 MPa.

## What do 3 lines on a bolt head mean?

The markings can identify the standard to which the bolt was made. For instance, if a bolt head contains three radial lines, then it’s a Grade 5 bolt. If it contains five radial lines, then the bolt is Grade 8.

Grade 8 bolts have been hardened more than grade 5 bolts. Thus they are stronger and are used in demanding applications such as automotive suspensions. Grade 8 bolts have 6 evenly spaced radial lines on the head. Grade G is roughly equivalent to Grade 8.

## How do I choose the right bolt?

This is how you choose the right bolt for the joint:

1. First, identify the load case.
2. Determine the necessary clamping force in the joint.
3. Choose the smallest bolt diameter that can support the clamp load.
4. Choose an effective bolt securing method.
5. Decide on the most appropriate tightening method.

## Is a longer bolt stronger?

The longer the bolt length acting within the joint affects it’s stiffeners IE longer = more deflection and obviously shorter = less deflection of the bolt.

## What does a 1/4 20 screw mean?

So when you read a bolt that says 1/4″-20 x 2″, that means, 1/4″ inch diameter, 20 threads TPI that’s threads per inch, which would be here,and then 2 inches long. 2 inches long would be from under the head to the end of the bolt. … Thread pitch is the distance between the peaks in millimeters.

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## What does m20 bolt mean?

M10-1.0 x 20

M = This designates the fastener is a metric size. 10 = The nominal diameter in millimeters. 1.0 = The thread pitch, or distance between threads, in millimeters. 20 = The fastener’s length, in millimeters.