AF was introduced much later and refers to Across Flats and was related to UNC(universal national coarse) and UNF(universal national fine) threads in the USA A 1/2 inch Whitworth socket is for a nut that fits on a 1/2 inch diameter thread, and is usually 1.5 times the diameter of the screwed rod across the flats of the ...
What does AF stand for on spanners?
Width across flats is the distance between two parallel surfaces on the head of a screw or bolt, or a nut, mostly for torque transmission by positive locking. The term width across flats (AF) is used for the following forms: 2-socket = round material with two surfaces. 4-socket = profile square section.
Are Whitworth and AF spanners the same?
The ‘sizes’ of Whitworth spanners refers to the diameter of the threaded stud, and not the bolt head itself: it is not an AF system. For this reason, BSF spanners are one size larger than the equivalent BSW, despite the fact that the bolt head is exactly the same size .
What are Whitworth spanners?
A whitworth spanner or socket is larger than one marked with the same size in BSF for example a 1/4 inch whit is the same physical size as a 5/16inch BSF. (approx 13.34mm),this occurs throught the sizes so a set of whitworth sockets or spanners will fit an equal number of BSF nuts and bolts.
Is Whitworth the same as imperial?
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard , devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard.
What is 16mm in AF?
| Inches Millimeters Spanner | 0.625 5/8 AF | 0.630 16mm 16mm | 0.669 17mm 17mm | 0.686 11/16 AF |
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What does AF mean in sockets?
AF can stand for American Fractional; another term used for imperial. However, when applied to metric sockets, AF means ‘ Across Flats ‘. This means a 19mm AF socket will fit a nut or bolt head that measures 19mm across its flats.
Are Whitworth threads still used?
British Standard Whitworth (BSW) Thread Form. Sir Joseph Whitworth proposed this thread in 1841. ... The thread form is now redundant and has been replaced by Unified and Metric threads but there are many applications in which it is still used .
What does SAE stand for?
SAE originated in the early 1900s as the Society of Automobile Engineers but soon became the Society of Automotive Engineers, a move that reflected its growing influence beyond the automobile.
What is an AF thread?
AF isn’t a thread type, it’s “Across Flats” and is just a way of measuring the size of a bolt head, so UNF and UNC bolts have head sizes that are specified by measuring them Across the Flats instead of relating them to the thread size as with Whitworth and BA.
When did Whitworth stop being used?
Whitworth and BSF officially became obsolete in 1948 following an agreement between the UK, US, and Canada to standardise on the American UNC and UNF fasteners for future use.
How do you identify Whitworth threads?
Use the Teesing thread gauge to determine the pitch or the TPI. The pitch is indicated in metric thread in millimeters. Whitworth thread is indicated in the number of threads per inch . Locate the possible TPI or pitch by matching the diameter measured with the thread tables below.
What is the difference between AF and Imperial?
Imperial are another range of sizes completely ;tend to be found on older UK vehicles. Most people take imperial to be inch sizes which are AF. If you’re thinking of Whitworth then you’ll struggle to get a whit set for cheap money these days. Most AF sizes are useful for when the metric nut is rounded etc.
How do I know if my threads are metric or imperial?
Metric threads are measured by their pitch . That is the distance from the crest of one thread to the crest of the next measured in millimetres. The pitch of a metric thread can be checked by direct measurement with a metric rule. Imperial threads have their pitch measured indirectly as a given number of teeth per inch.
Is BSP a Whitworth thread?
BSP threads have rounded valleys and troughs with a 55 degree pitch (this is known as Whitworth type). There are two types of BSP threads; Tapered (BSPT) and parallel (BSPP). ... The table below summarises BSP sizes to help with general identification.
What size is a 9/16 spanner?
| BOLT DIAMETER (INCHES) AF SPANNER SIZE (INCHES) SPANNER SIZE (MM) | 1/4 INCH 7/16 INCH 11.11 MM | 5/16 INCH 1/2 INCH 12.7 MM | 3/8 INCH 9/16 INCH 14.29 MM | 7/16 INCH 5/8 INCH 15.88 MM |
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