Bolts: mechanical parts, cylindrical threaded fasteners with nuts, a type of fasteners composed of two parts, the head and the screw (cylinder with external threads), which need to be matched with the nut for tightening Two parts with through holes are firmly connected.

This connection form is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a for detachable connection.

Measuring bolt

Knowing how to find the diameter and length of the fastener is an important first step in obtaining the correct fastener.

Measuring bolt diameter

To measure the diameter of screws and bolts, measure the distance from the external thread on one side to the external thread on the other side.

This is called the large diameter and is usually the appropriate size for the bolt.

You can also measure from one side to the other side of the threaded bottom cavity to find the smaller diameter.

Simple method (not precise enough)
Use vernier calipers and bolts to measure the thread of the outer dao, and the nut to measure the bottom of the thread of the screw. According to the measured value, use the closest standard size.

Easier way
Find a set of fixed-value bolts and nuts (the principle is the same as the plug gauge).

And then use these standard items and the matching you want to measure (for example, use m20 bolts to measure suspected m20 nuts, if they can be screwed together, then Explain that the nut is m20), it is very convenient to know.

Measurement of hexagon bolts:
To measure hexagonal bolts, you must use a caliper. The measuring method is generally to measure the thread diameter and thread length.

If it is half-threaded, in addition to measuring the thread length, the diameter of the light rod and the total length of the polished rod and the thread are also measured.

The diameter of the polished rod and the diameter of the thread can be compared to determine whether this screw needs to be reduced.

After the thread is measured, the pitch can be measured, And then measure the head. If it is a hexagonal head, you need to measure the opposite side of the hexagon. The diagonal can be measured but not because the opposite side can be calculated.

Then measure the thickness of the hexagon again. If it is an internal hexagon, not only the opposite side of the hexagon, but also the depth of the hexagon, then the diameter and thickness of the head.