What do the markings on the head of a bolt mean?

The markings on the heads of bolts serve two different purposes: The markings can indicate who manufactured the bolt. This will vary from manufacturer to manufacturer, but is usually one, two or three characters. The markings can identify the standard to which the bolt was made.

How do you identify a hex bolt?

As a general rule, the length of fasteners is measured from the surface of the material, to the end of the fastener. For fasteners where the head usually sits above the surface such as hex bolts and pan head screws, the measurement is from directly under the head to the end of the fastener.

What do the numbers on top of bolts mean?

The number has nothing to do with the size, but does indicate the relative strength of the bolt. The higher the number, the stronger the bolt. Some metric nuts are also marked with a single-digit number to indicate the strength, and some may have the M and strength grade embossed on the flats of the hex.

What does 3 lines on bolt head mean?

Three radial lines will indicate an SAE grade 5 fastener, while six radial lines will indicate an SAE grade 8 fastener. These are the most common grades, but there are others.

How Will Head of Grade 5 Unified bolt be marked?

Grade 5. So as you can see, this bolt head has Wilson-Garner’s manufacturer mark and three radial lines. These lines indicate that the bolt is a Grade 5. Grade 5 fasteners have a minimum tensile strength of 120ksi for diameters ¼ inch through 1 inch and 105ksi for diameters over 1 inch through 1-1/2 inches.

What are bolt grade markings?

The grade of a bolt determines the maximum amount of stress (tensile strength) that the bolt can handle. The SAE marking system uses raised dashes on the bolt head to indicate strength. Metric Bolt Grades—Metric grades are set according to rules set by the ISO (International Standards Organization).

How do you measure a hex bolt head?

They are measured from the top of the head to the tip. Hex and hex washer head screws and bolts, although flat on the top and the bottom, are measured from the bottom of the head. Oval head screws are an exception to the rule. The starting point for their length is at the widest point of the head.

What size bolt has a 24mm head?

Size Chart

What are the different types of bolt heads?

What do you call a bolt without head?

Set screws are most often headless (aka blind), meaning that the screw is fully threaded and has no head. A blind set screw, known in UK as a grub screw, is almost always driven with an internal wrenching drive, such as a hex Allen key.

What are the markings on the head of a bolt?

Most bolt markings are found on the fastener head. They can be a combination of numbers and letters or a pattern of lines. Nuts tend to have much smaller markings, although they are also made of numbers and letters or lined patterns.

What do the markings on a stainless steel bolt mean?

The marks shown on the head of a bolt represent the hardness of the bolt. No marks indicate the softest bolt, whereas three marks indicate medium hardness and six marks indicate the hardest. What grade are stainless steel bolts? Usually, stainless steel bolts come in 18-8/304 stainless steel or 316 stainless steel grades.

The grade mark is a standardised mark that identifies the material properties that the fastener meets. For example 307A on a bolt head indicates that the fastener properties conform to the ASTM A307 Grade A standard. The bolt head shown at the side indicates that it is of property class 8.8 and ML is the manufacturer’s mark.

What are the dimensions of a hex head?

Typically, machine bolt sizes range from 1/4″ to 1 1/4″ for square heads and 3/8″ to 1 3/4″ in diameter for hex heads, and lengths span from about 3/4″ to 18″ for square and 6 1/2″ to 24″ for hex heads. Measure length from under the head to the threaded end of the bolt. Both square and hex heads are available.