British Standard Fine (BSF) is a screw thread form, as a fine-pitch alternative to British Standard Whitworth (BSW) thread. It was used for steel bolts and nuts on much British machinery, including cars, prior to adoption of Unified, and later Metric, standards. For highly stressed conditions, especially in motorcycles, a finer thread, British Standard Cycle (BSC), was used as well.
BSF was developed by R. E. B. Crompton, and his assistant George Field.BSF threads use the 55 degree Whitworth thread form. It was introduced by the British Engineering Standards Association in 1908.
The table provides BSF sizes, the threads per inch and spanner jaw sizes. The BSC column indicates where BSF and BSC threads match. The table shows suitable tapping drill sizes. Uncommon sizes are shown in italics.
|As BSC?||Nut||Tap drill|
|3⁄16||0.19||4.83||32||Yes||8.59||11⁄32 6pt||5⁄32 in|
|5⁄8||0.63||16.00||14||25.65||1 6pt||14 mm|
|11⁄16||0.69||17.53||14||27.94||1 1⁄8 6pt||15.5 mm|
|3⁄4||0.75||19.05||12||30.48||1 1⁄4 6pt||16.75 mm|
|7⁄8||0.88||22.35||11||33.02||1 5⁄16||25⁄32 in|
|1||1.00||25.40||10||37.59||1 1⁄2||22.75 mm|
|1 1⁄8||1.13||28.70||9||42.42||1 11⁄16||26.50 mm|
|1 1⁄4||1.25||31.75||9||47.24||1 7⁄8||28.75 mm|
|1 1⁄2||1.50||38.10||8||56.39||2 1⁄4||34.50 mm|
An adjustable spanner or adjustable wrench is an open-end wrench with a movable jaw, allowing it to be used with different sizes of fastener head rather than just one fastener size, as with a conventional fixed spanner. Several other names are in use, including casually imprecise use of the US trademark crescent wrench.
A micrometer, sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw widely used for accurate measurement of components in mechanical engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier, and digital calipers. Micrometers are usually, but not always, in the form of calipers. The spindle is a very accurately machined screw and the object to be measured is placed between the spindle and the anvil. The spindle is moved by turning the ratchet knob or thimble until the object to be measured is lightly touched by both the spindle and the anvil.
A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning.
Taps and dies are tools used to create screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair. A die is used to cut or form the male portion of the mating pair. The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.
The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.
A collet is a subtype of chuck that forms a collar around an object to be held and exerts a strong clamping force on the object when it is tightened, usually by means of a tapered outer collar. It may be used to hold a workpiece or a tool.
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In drills and mills it holds the rotating tool whereas in lathes it holds the rotating workpiece. On a lathe the chuck is mounted on the spindle which rotates within the headstock. For some purposes an additional chuck may be mounted on the non-rotating tailstock.
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, based on the Whitworth thread devised and specified by Joseph Whitworth in 1841, which was the world's first national screw thread standard,
British Association screw threads, or BA screw threads, are a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter. They were, and to some extent still are, used for miniature instruments and modelling.
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most common forms used for leadscrews. They offer high strength and ease of manufacture. They are typically found where large loads are required, as in a vise or the leadscrew of a lathe. Standardized variations include multiple-start threads, left-hand threads, and self-centering threads.
British Standard Pipe (BSP) technical standards for screw threads that has been adopted internationally for interconnecting and sealing pipes and fittings by mating an external (male) thread with an internal (female) thread. It has been adopted as standard in plumbing and pipe fitting, except in North America, where NPT and related threads are used.
The ISO metric screw thread is the most commonly used type of general-purpose screw thread worldwide. They were one of the first international standards agreed when the International Organization for Standardization (ISO) was set up in 1947.
A screw and a bolt are similar types of fastener typically made of metal, and characterized by a helical ridge, known as a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in the matching part.
United States Standard thread, also known as Sellers Standard thread, Franklin Institute thread and American Standard thread, is a standard for inch based threaded fasteners and washers.
British Standard Cycle is a British Imperial screw thread standard. Unlike other major British imperial thread standards the thread runs at a 60 degrees rather than a 55 degrees angle. All sizes 1⁄4 inch and larger use 26 threads per inch (tpi), making them similar to 1 mm ISO threads, which are 25.4 per inch and also run at a 60 degrees angle. It was originally used with both bicycles and motorcycles. However it is now believed to be obsolete in motorcycle manufacture. In the bicycle industry it is still found on virtually all bottom bracket threads and the wheel axles of low-end models manufactured in China.
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 Swiss-designed Thury screw thread is a metric thread standard that was developed in the late nineteenth century for screws used in scientific and horological instruments. The thread is named after Marc Thury, an engineer and professor at the University of Geneva who contributed heavily to the standard's development.
The Löwenherz thread is a largely obsolete metric thread form designed in the late nineteenth century and frequently applied in precision instruments. It is named after Dr. Leopold Löwenherz, who was the director of the metrology institute Physikalisch-Technische Bundesanstalt in Berlin.