The grade of a hex bolt indicates its strength and hardness. Common grades in the U.S. are Grade 2, Grade 5, and Grade 8. Each grade has a specific marking on the head, like two marks for Grade 5 and six marks for Grade 8. Higher-grade bolts (e.g., Grade 8) are stronger and can withstand more stress, making them suitable for demanding applications. Choosing the right grade is essential for safety and durability, as an under-graded bolt could fail under load, potentially leading to structural failure.

Fully threaded hex bolts have threads running from the tip to just beneath the head, making them ideal for situations requiring adjustable length or secure threading along the bolt’s full length. Partially threaded hex bolts, with a smooth shank between the threads and head, offer more shear strength, as the unthreaded section can better withstand side-to-side forces. The choice depends on the application’s requirements, such as tension and shear loads, with partially threaded bolts often preferred for load-bearing connections.

Coatings, such as zinc, black oxide, or galvanization, are applied to hex bolts to enhance their resistance to corrosion. Zinc-coated bolts, for example, are commonly used in damp environments, as the zinc acts as a barrier against rust. Galvanized bolts, with a thicker zinc coating, are even more corrosion-resistant, ideal for outdoor or marine applications. Coatings also improve the bolt's appearance and can reduce friction, making installation easier. Selecting the right coating depends on the environment and expected lifespan of the fastener.