BSF Bolts Part Thread Grade R

What are BSF part-thread bolts?

These are high tensile carbon steel hex bolts, Grade R, with a British Standard Fine thread. BSF has a finer pitch—more threads per inch (TPI)—than British Standard Whitworth (BSW) at the same nominal diameter. A BSF bolt will not fit a BSW nut or tapped hole of the same diameter.

The shaft is partly threaded, leaving a plain, unthreaded section beneath the head. The hex head is tightened with a suitable spanner or socket.

Where would I use BSF bolts?

BSF fixings are found on older British vehicles, motorcycles, machinery and engineering equipment. These bolts are for repairs and restoration where the assembly calls for a high tensile Grade R BSF bolt with a partly threaded shaft.

Replacing the correct thread helps you retain existing nuts and tapped components. Check the original fixing or parts specification: an older British vehicle or machine may contain more than one thread system.

Is BSF the same as UNF?

No. British Standard Fine and Unified National Fine are different thread standards. Both are described as fine threads, but a UNF bolt is not a direct replacement for a BSF bolt. Check the thread type as well as the diameter.

Part thread or full thread?

Choose the form specified for your joint. If you need thread along the shaft, see our BSF fully threaded hex setscrews, also high tensile Grade R.

How do I choose the size and finish?

Match the diameter and TPI, then measure bolt length from underneath the head to the tip. The head is not included in the length.

Choose the finish shown for your selected size. Our fastener coating guide explains self colour and plated finishes.

Which nuts fit BSF bolts?

Use BSF nuts with the same diameter and TPI, and the strength specification required for the joint. Add appropriately sized imperial washers where needed.

Unsure which thread you have? Start with our imperial thread identification guide.

All Available Sizes & Types

All Available Sizes & Types