About Hex Head Screws and Bolts

Understanding Threading

Fully threaded screws engage with a tapped, threaded hole all the way to the head. Choose these when sideways force is not a concern.

Partially threaded screws have an unthreaded portion under the head for more holding power when force is applied from the side. The unthreaded portion is stronger than the threaded portion of the screw. Thread length may vary from the minimum thread length published to fully threaded.

Understanding Thread Size

Inch

Inch thread sizes are specified by diameter and threads per inch. Diameter is also known as screw size. For those with a diameter smaller than 1/4″, screw size is indicated by a number (e.g., #10 or No. 10).

Metric

Metric thread sizes are specified by diameter and pitch, which is the space between threads. For the size M6 × 1 mm, the pitch is coarse; while the size M6 × 0.75 mm has a fine pitch. If you don’t know the pitch, choose coarse threads; they’re the industry standard.

Comparing Materials by Strength and Corrosion Resistance

Use this chart to compare the trade-offs between strength and corrosion resistance in different environments.