Missed our Which Thread blog post? No worries read again here.
At Arun Fasteners, we stock a variety of thread options for all types of fasteners. Below is a brief summary of the main types and where they are used.
The most widely used thread today, ‘ISO Metric’ or ‘M’ for short. Available in coarse and fine threads in most materials and sizes, also DIN standards are very popular.
They come in a variety of strengths:
Grade 4.8 – Mild to medium carbon steel, common for machine screws and threaded bar.
Grade 8.8 – High tensile carbon steel, common for metric hex head bolts and setscrews
Grade 10.9 – High tensile alloy steel, common for metric hex head bolts and setscrews and socket screws
Grade 12.9 – High tensile alloy steel, common for metric hex head bolts, setscrews and socket screws.
UNC meaning Unified Coarse, is the most dominant used in the USA. Often used in the agricultural industry because of their strong coarse threads. Generally available in steel and stainless steel. Come in higher grades – (S) high tensile and higher grades available.
UNF meaning Unified Fine, also a dominant thread in the USA. Often used in the automobile industry because of their tight fine threads. Generally available in steel and stainless steel. Come in higher grades – (S) high tensile and higher grades available.
BA meaning British Association, old-style British thread with numbered diameters; 16BA being the smallest and 0BA the largest. Thread lengths are determined in inches and available in most materials.
BSF meaning British Standard Fine, an old style British thread. Often used on vintage British automobiles and machinery as its fine thread is preferred. Available in steel and stainless steel although stainless can now be difficult to source.
British Standard Whitworth (WHIT or BSW)
The original 19th century British coarse-threaded industrial bolts designed to hold locomotives together. Because of their coarse pitch, they are prone to vibrating loose, so are little used on motorcycles. Most sizes are interchangeable with UNC threads except ½” but do have a slightly different angle on the thread, however, this practice is ill-advised with stress fixings such as brakes or suspension components. Available in steel and stainless.