What Style
These styles are a guide to the common, mass-produced fastener over different periods of time. Most manufacturers designed their products using the common fastener to keep the price of manufacture low. Specialised fasteners or fasteners with additional options were generally only used when necessary. The finishing applied to fasteners is also part of style. To try and keep it simple we have split style into two, this section is the physical style of the fastener. The section on the finish can be found here.
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Fasteners have changed over the last hundred years or so with advances in materials science. Both the quality of the metal improved and the costs of manufacturing were reduced.
There are two time periods that we do not sell. The Early period prior to around 1908 which consists of non-standardised and trade association or company standardised fasteners that are best reproduced in small batches that are copied from original articles, and the Current period that are readily available from many sources. There are three more distinct periods of the vintage and classic fasteners that we do sell, Pre-WWII, WWII and Modern.
Fasteners did not suddenly appear to style but like the standards that form them evolved over time. A standard took what was good at that time and formalised it. It takes time for the changes of a standard to take effect and for the many people to improve, produce, and use fasteners before a change is reflected in a standard making the fasteners within the periods somewhat flexible.
Pre-WWII Period
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Large sized nuts and bolt heads with a single chamfer to the upper face with a full bearing unchamfered lower face to both nuts and bolt heads. The lower face only of a nut was countersunk to help the nut engage onto the thread of a bolt or stud. Bolt and stud ends were generally rounded with a chamfer or rolled towards the centre to again help engage with a nut or threaded socket. This style continued until the metal saving standards of WWII were issued.
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There were also smaller sized nut and bolts heads designed for the automobile industry which also made their way into the aircraft and many other industries. The reduced size nut and bolt head standard appeared 1911. The size reduction was one spanner size down. To cope with the additional standard spanners were made with the two different sizes marked on the same end. Some of the intermediate sizes such as 9/32" and 5/16" were given the same head size as the next larger size.
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BA nuts and bolts followed the same style patten.
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The 1902 Cycle Engineers’ Institute, CEI threaded nuts and bolts used the same size heads and nuts as BSF or BSW. CEI was standardised just before WWII as BSC, British Standard Cycle. There are four series of threads in the BSC standard, those with a 60° flank angle and those with a 55° Whitworth flank angle. The series are BSC bolts and nuts, BSC spokes and nipples, BSC for special applications and BSW bolts and nuts (20TPI). The BSC bolts and nuts series is often called 26 TPI Cycle Thread as this number of thread per inch run from 7/32" diameter to 3/4" but the series also has 40TPI at 1/8" and 32TPI at 5/32" and 3/16. The BSC (20TPI) series often called 20TPI Cycle Thread uses the Whitworth 55° flank angle with diameters running from 7/16" to 3/4" at the same 20TPI. The BSC for special applications covers cycle and motorcycle crank cotters, steering columns, lock rings for sprockets, and bearing cups.
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Whitform is a set of threads that are not in the above standards. These might be threads that were originally included such as the 3/16" range of bolts and nuts, or they might a thread with the Whitworth form of but a different number of threads for the diameter of bolt or nut.
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WWII Period
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The style remained the same as pre-war but to save metal for the war effort the size of nuts and bolt heads were reduced. Lock nuts went from a full bearing to lower face to double chamfered and countersunk on both sides to make mounting easier.
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Post WWII
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Improved manufacturing processes brought down the costs of the additional options to nuts and bolt heads. The majority of nuts became double chamfered and countersunk on both sides. With both sides identical it no longer mattered which way round a nut was used. Bolt heads were full bearing with the addition of a washer face. The double chamfered, washer face was also a popular alternative type.
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This period begins with the rise of the Unified standard of fasteners.
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Modern
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Although there are still Imperial fasteners made this is the period the Imperial fastener standards have not changed. This period is the rise of the Metric fastener.
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