What do the markings on nuts mean?
Bolt heads and nuts are often marked with numbers, letters, dashes, slashes, dots, or an assortment of other marks. Fasteners commonly have two different markings: a unique manufacturer identification symbol – such as letters or an insignia – and information about the fastener strength.
What do the numbers mean on nuts and bolts?
The bigger the number, the thicker the shank. 24 – Represents the number TPI, or the number of threads per inch. The higher the number, the finer the threads, which are best used in metal applications.
How can you tell if a 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.
Is class 10.9 the same as Grade 8?
Class 10.9 is stronger than class 8.8. It is commonly found in high strength automotive applications. Class 10.9 is similar to grade 8. A low carbon steel for general use.
How do you read bolt markings?
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. 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.
How can you tell the difference between standard and metric threads?
Metric vs standard 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.
What do letters mean on bolts?
The three-letter code is the manufacturer code (for example, HKT stands for Hau Kwang Enterprises) and the numbers (if metric) or radial lines (if SAE) refer to the bolts’ strength. If there are no numbers or lines present, assume the bolt is no better than a grade 2 (low strength).