WHITWORTH Bolts Part Thread Grade R

What are Whitworth part-thread bolts?

Whitworth bolts use the British Standard Whitworth thread, usually shortened to BSW or WHIT. This is the coarse thread in the Whitworth family, with fewer threads per inch (TPI) than BSF at the same nominal diameter. BSW and BSF are not interchangeable.

These hex bolts are partly threaded, leaving a plain, unthreaded section beneath the head. The high tensile steel options are Grade R. Stainless steel and brass options, where listed, have different material specifications and are not Grade R steel.

Where would I use them?

These bolts are for repairs and restoration of older machinery, vehicles and equipment that already use BSW fixings. Choose the part-thread form where the original joint calls for a bolt with a plain section beneath the head.

Match the original thread, material, required strength and bolt form. Age or appearance alone will not identify the correct fixing.

Is Whitworth the same as UNC?

No, some BSW and UNC sizes have the same diameter and TPI, but their thread profiles differ: BSW uses a 55-degree thread angle, while UNC uses 60 degrees. They can be interchangeable, apart from 1/2″.

Part thread or full thread?

If the joint requires thread along the shaft, compare our Whitworth fully threaded hex setscrews. Choose the form and material specified for the assembly.

Are all finishes high tensile Grade R

All of our Self Colour, Zinc and Zinc Yellow bolts are high tensile Grade R. Those products that are stainless or brass are not high tensile.

How do I choose the size and finish?

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

Select the material and finish offered for your chosen size. Our fastener coating guide explains self colour and plated finishes.

Which nuts fit Whitworth bolts?

Use Whitworth/BSW nuts with the same diameter and TPI, and the material and strength needed for the joint. Add appropriately sized imperial washers where required.

Unsure of the thread? Compare it using our imperial thread identification guide.

WHITWORTH/BSW TPI Chart

All Available Sizes & Types