A hex key, Allen wrench or Allen key, is a simple tool used to drive bolts and screws with hexagonal sockets in their heads. The tool is formed of a single piece of hexagonal rod of hard steel, with blunt ends that are meant to fit snugly into the screw's socket, bent in an "L" shape with unequal arms; the tool is held and twisted by the long arm, creating a large torque at the tip of the short arm. Reversing the tool lets the long arm reach screws in hard-to-reach places; each key is meant to be used with rather tight tolerances. The size of the key increases with the size of the socket, but not in direct proportion. Variants of the tool have the short end inserted in a transverse handle, which may contain multiple keys that can be folded into the handle when not in use; the "Allen" name is a registered trademark, originated by the Allen Manufacturing Company of Hartford, Connecticut circa 1910, owned by Apex Tool Group, LLC. Its genericised use is discouraged by this company; the standard generic name used in catalogues and published books and journals is "hex key".
Explained by the geographical and commercial history of the drive type's development, the term "hex key" is best known as "Allen" in the USA, in Spain, as "Inbus" in Germany, as "Unbrako" key or wrench in Scandinavia. In Italy, it is known for the company Officine Egidio Brugola; the term "hex-head" is sometimes used to refer to this type of drive, but this use is not consistent with its more conventional use referring to external-wrenching hexagons. In the fastener industry, the terms "socket head" or "hex socket head" are used for the driven part of the driver–driven pair. A less common synonym is "female hex"; some features of hex keys are: The tool is simple and light. The contact surfaces of the screw or bolt are protected from external damage. There are six contact surfaces between driver. Small bolt heads can be accommodated; the tool allows the use of recessed-head screws. The screw can be held by the key; the torque applied to the screw is constrained by the thickness of the key. The tool is cheap, so it can be included with products requiring end-user assembly.
Either end of the tool can be used to take advantage of torque. The tool can be reconditioned using an electric grinder by removing the worn-out part near the end. High torque is more to damage an internal socket/key than an external hexagon head/wrench It is much more difficult to turn a damaged internal fastener than an external one; the scant documentation available indicates that the idea of a hex socket screw drive was conceived as early as the 1860s to the 1890s, but that such screws were not manufactured until around 1910. Rybczynski describes a flurry of patents for alternative drive types in the 1860s to the 1890s in the US, which are confirmed to include internal-wrenching square and triangle types, but he explains that these were patented but not manufactured due to the difficulties and expense of doing so at the time. P. L. Robertson, of Milton, Canada, first commercialized the square socket in 1908, having perfected and patented a suitable cold forming method, using the right material and the right die design.
In 1909–1910, William G. Allen too patented a method of cold-forming screw heads around a hexagonal die. Published advertisements for the "Allen safety set screw" by the Allen Manufacturing Company of Hartford, exist from 1910. Although it is unlikely that Allen was the first person to think of a hex socket drive, his patent for a manufacturing method and his realized product appear to be the first. In his autobiography, the founder of the Standard Pressed Steel Company, Howard T. Hallowell Sr, presents a version of events in which SPS developed a hex socket drive in-house, independently of Allen, circa 1911. From this came the Unbrako line of products; this account from Hallowell does not mention the Allen patent of 1910, nor the Allen safety set screw product line. Hallowell does describe, the same inspiration mentioned in connection with Allen for a wave of adoption of the hex socket head, beginning with set screws and followed by cap screws; this was an industrial safety campaign, part of the larger Progressive Movement, to get headless set screws onto the pulleys and shafts of the line shafting, ubiquitous in factories of the day.
The headless set screws would be less to catch the clothing of workers and pull them into injurious contact with the running shaft. SPS at the time was a prominent maker of shaft hangers and collars, the latter of which were set in place with set screws. In pursuit of headless set screws with a better drive than a straight slot, Hallowell said, SPS had sourced set screws of square-socket drive from Britain, but they were expensive. (This was only 2 years after Robertson's Canadian
A bicycle called a cycle or bike, is a human-powered or motor-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A bicycle rider is called bicyclist. Bicycles were introduced in the late 19th century in Europe, by the early 21st century, more than 1 billion were in existence at a given time; these numbers far exceed the number of cars, both in total and ranked by the number of individual models produced. They are the principal means of transportation in many regions, they provide a popular form of recreation, have been adapted for use as children's toys, general fitness and police applications, courier services, bicycle racing and bicycle stunts. The basic shape and configuration of a typical upright or "safety bicycle", has changed little since the first chain-driven model was developed around 1885. However, many details have been improved since the advent of modern materials and computer-aided design; these have allowed for a proliferation of specialized designs for many types of cycling.
The bicycle's invention has had an enormous effect on society, both in terms of culture and of advancing modern industrial methods. Several components that played a key role in the development of the automobile were invented for use in the bicycle, including ball bearings, pneumatic tires, chain-driven sprockets and tension-spoked wheels; the word bicycle first appeared in English print in The Daily News in 1868, to describe "Bysicles and trysicles" on the "Champs Elysées and Bois de Boulogne". The word was first used in 1847 in a French publication to describe an unidentified two-wheeled vehicle a carriage; the design of the bicycle was an advance on the velocipede, although the words were used with some degree of overlap for a time. Other words for bicycle include "bike", "pushbike", "pedal cycle", or "cycle". In Unicode, the code point for "bicycle" is 0x1F6B2; the entity 🚲. The "Dandy horse" called Draisienne or Laufmaschine, was the first human means of transport to use only two wheels in tandem and was invented by the German Baron Karl von Drais.
It is regarded as the modern bicycle's forerunner. Its rider sat astride a wooden frame supported by two in-line wheels and pushed the vehicle along with his or her feet while steering the front wheel; the first mechanically-propelled, two-wheeled vehicle may have been built by Kirkpatrick MacMillan, a Scottish blacksmith, in 1839, although the claim is disputed. He is associated with the first recorded instance of a cycling traffic offense, when a Glasgow newspaper in 1842 reported an accident in which an anonymous "gentleman from Dumfries-shire... bestride a velocipede... of ingenious design" knocked over a little girl in Glasgow and was fined five shillings. In the early 1860s, Frenchmen Pierre Michaux and Pierre Lallement took bicycle design in a new direction by adding a mechanical crank drive with pedals on an enlarged front wheel; this was the first in mass production. Another French inventor named Douglas Grasso had a failed prototype of Pierre Lallement's bicycle several years earlier.
Several inventions followed using rear-wheel drive, the best known being the rod-driven velocipede by Scotsman Thomas McCall in 1869. In that same year, bicycle wheels with wire spokes were patented by Eugène Meyer of Paris; the French vélocipède, made of iron and wood, developed into the "penny-farthing". It featured a tubular steel frame on; these bicycles were difficult to ride due to poor weight distribution. In 1868 Rowley Turner, a sales agent of the Coventry Sewing Machine Company, brought a Michaux cycle to Coventry, England, his uncle, Josiah Turner, business partner James Starley, used this as a basis for the'Coventry Model' in what became Britain's first cycle factory. The dwarf ordinary addressed some of these faults by reducing the front wheel diameter and setting the seat further back. This, in turn, required gearing—effected in a variety of ways—to efficiently use pedal power. Having to both pedal and steer via the front wheel remained a problem. Englishman J. K. Starley, J. H. Lawson, Shergold solved this problem by introducing the chain drive, connecting the frame-mounted cranks to the rear wheel.
These models were known as safety bicycles, dwarf safeties, or upright bicycles for their lower seat height and better weight distribution, although without pneumatic tires the ride of the smaller-wheeled bicycle would be much rougher than that of the larger-wheeled variety. Starley's 1885 Rover, manufactured in Coventry is described as the first recognizably modern bicycle. Soon the seat tube was added. Further innovations increased comfort and ushered in a second bicycle craze, the 1890s Golden Age of Bicycles. In 1888, Scotsman John Boyd Dunlop introduced the first practical pneumatic tire, which soon became universal. Willie Hume demonstrated the supremacy of Dunlop's tyres in 1889, winning the tyre's first-ever races in Ireland and England. Soon after, the rear freewheel was developed; this refinement led to the 1890s invention of coaster brakes. Dérailleur gears and hand-operated Bowden cable-pull brakes were developed during these years, but were only adopted by casual riders; the Svea Velocipede with vertical pedal arrangement and
Sheldon Brown (bicycle mechanic)
Sheldon Brown was an American bicycle mechanic, technical expert and author. He contributed to print and online sources related to bicycling and bicycle mechanics, in particular the web site Sheldon Brown's Bicycle Technical Info, his knowledge of bicycles was described as "encyclopaedic" by The Times of London. Brown was the parts manager and technical consultant of Harris Cyclery, a bike shop in West Newton, Massachusetts, as well as an enthusiast of vintage and classic bicycles in addition to cycling in general. Brown maintained Sheldon Brown's Bicycle Technical Info, a web site highlighting a broad range of cycling subjects ranging from how to fix a bicycle flat tire to details on Raleigh and English three-speed bicycles, Sturmey-Archer hubs and fixed-gear bicycles, he was an amateur photographer. His site features his photographic work. Brown maintained an English-French cycling dictionary, having lived and cycled in France and written about his family's travels in France. After developing nerve deterioration over the last years of his life, Brown lost his ability to ride an upright bicycle and continued riding with a recumbent tricycle.
In August 2007, Brown was diagnosed with primary progressive multiple sclerosis. He died on February 4, 2008 in Newton, after a heart attack. Brown was an atheist. Brown's website, developed with Harris Cyclery, includes a knowledgeable and accessible database of technical bicycle information. In particular a wide selection of knowledge of common bicycles from the second half of the 20th century that use non-standard parts; the site remains current as of 2018—the commercial pages are maintained and updated by Harris Cyclery employees, the informational pages by his widow, Harriet Fell, his friend John Allen, "a nationally recognized bicycling expert who helped found the Cambridge Bicycle Committee." Brown maintained the site's glossary of bicycling terminology, online guide to wheelbuilding, as well as the mirror sites of the technical work of Damon Rinard, Jobst Brandt, others. Brown had participated in online cycling forums such as rec.bicycles.tech newsgroup and bikeforums.net. Brown was a proponent of single-speed bicycles for ordinary street use.
Brown, with Galen Evans and Osman Isvan, developed a method to determine and compare bicycle gear ratios. For any combination of front chainring, rear cog, wheel size and crank length, his method results in a number that Brown terms the "gain ratio". Brown expressed personal opinions on chain cleaning and wear, a source of controversy in the field of bicycle maintenance. In addition to the wide array of bike mechanics and repair articles, Brown's website contains sections on family cycling, touring, a bike humor section, as well as essays and fiction about cycling, his humorous online articles appeared on April 1. Brown was a contributing writer for Bike World magazine and for Bicycling magazine, for the trade magazine American Bicyclist. Brown wrote the "Mechanical Advantage" column for Adventure Cyclist, the magazine of the Adventure Cycling Association, "from 1997 through 2007."In October 2003, Brown was awarded a certificate of commendation for his contribution to cycling by the UK's Cyclists' Touring Club.
Brown received the Classic Rendezvous Vintage Bicycle Award in 2005. MassBike presented Brown the Influence Pedaler Award posthumously in 2008. CTC's Chris Juden mentioned Brown's site in his response to a letter to the editor email, Lennard Zinn, technical editor for VeloNews, cited Brown in his regular Technical FAQ with Lennard Zinn column. Frank Berto cites Brown's writing in The Dancing Chain, published by Van der Plas Publications, Zack Furness cites Brown's writing in One Less Car: Bicycling and the Politics of Automobility, published by Temple University Press. Sheldon Brown's Bicycle Technical Info Harris Cyclery homepage
A sprocket or sprocket-wheel is a profiled wheel with teeth, or cogs, that mesh with a chain, track or other perforated or indented material. The name'sprocket' applies to any wheel upon which radial projections engage a chain passing over it, it is distinguished from a gear in that sprockets are never meshed together directly, differs from a pulley in that sprockets have teeth and pulleys are smooth. Sprockets are used in bicycles, cars, tracked vehicles, other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear motion to a track, tape etc; the most common form of sprocket may be found in the bicycle, in which the pedal shaft carries a large sprocket-wheel, which drives a chain, which, in turn, drives a small sprocket on the axle of the rear wheel. Early automobiles were largely driven by sprocket and chain mechanism, a practice copied from bicycles. Sprockets are of a maximum of efficiency being claimed for each by its originator. Sprockets do not have a flange.
Some sprockets used with timing belts have flanges to keep the timing belt centered. Sprockets and chains are used for power transmission from one shaft to another where slippage is not admissible, sprocket chains being used instead of belts or ropes and sprocket-wheels instead of pulleys, they can be run at high speed and some forms of chain are so constructed as to be noiseless at high speed. The term'sprocket' applied to the projection from the wheel that caught on the chain and provided the drive to it; the overall wheel was termed a'sprocket wheel'. With time and common use of these devices, the overall wheel became known as a sprocket; the earlier uses would now be seen as archaic. In the case of bicycle chains, it is possible to modify the overall gear ratio of the chain drive by varying the diameter of the sprockets on each side of the chain; this is the basis of derailleur gears. A multi-speed bicycle, by providing two or three different-sized driving sprockets and up to 12 different-sized driven sprockets, allows up to 36 different gear ratios.
The resulting lower gear ratios make the bike easier to pedal up hills while the higher gear ratios make the bike more powerful to pedal on flats and downhills. In a similar way, manually changing the sprockets on a motorcycle can change the characteristics of acceleration and top speed by modifying the final drive gear ratio; the final drive gear ratio can be calculated by dividing the number of teeth on the rear sprocket by the number of teeth on the counter-shaft sprocket. With respect to the stock gearing on a motorcycle, installing a smaller counter-shaft sprocket, or a larger rear sprocket, produces a lower gear ratio, which increases the acceleration of the motorcycle but decreases its top speed. Installing a larger counter-shaft sprocket, or a smaller rear sprocket, produces a higher gear ratio, which decreases the acceleration of the motorcycle but increases its top speed. In the case of vehicles with caterpillar tracks the engine-driven toothed-wheel transmitting motion to the tracks is known as the drive sprocket and may be positioned at the front or back of the vehicle, or in some cases both.
There may be a third sprocket, driving the track. Sprockets are used in the film transport mechanisms of movie projectors and movie cameras. In this case, the sprocket wheels engage film perforations in the film stock. Sprocket feed was used for punched tape and is used for paper feed to some computer printers. Roller chain Rack and pinion Toothed belt Gear train Chain drive Bicycle gearing Cogset Bicycle chain Cycling terminology Mechanical advantage Chain Engagement with Sprockets
Shimano, Inc. is a Japanese multinational manufacturer of cycling components, fishing tackle and rowing equipment. It produced golf supplies until 2005 and snowboarding gear until 2008. Headquartered in Sakai, the company has 32 consolidated subsidiaries and 11 unconsolidated subsidiaries. Shimano's primary manufacturing plants are in China. In 2017, Shimano had net sales of US $3.2 billion, 38% in Europe, 35% in Asia, 11% in North America. Bicycle components represented 80%, fishing tackle 19%, other products 0.1%. The company is publicly traded, with 93 million shares of common stock outstanding. Shimano sales constitute an estimated 70–80% of the global bicycle component market by value, its products include drivetrain, brake and pedal components for road, mountain and hybrid bikes. The components include: crankset comprising chainrings. Shimano Total Integration is Shimano's integrated shifter and brake lever combination for road bicycles; the Italian firm Campagnolo as well as US based SRAM are Shimano's primary competitors in the cycling marketplace.
When the 1970s United States bike boom exceeded the capacity of the European bicycle component manufacturers, Japanese manufacturers SunTour and Shimano stepped in to fill the void. While both companies provided products for all price-ranges of the market, SunTour focused on refinement of existing systems and designs for higher end products, while Shimano paid more attention to rethinking the basic systems and bringing out innovations such as Positron shifting and front freewheel systems at the low end of the market. In the 1980s, with Shimano pushing technological innovation and lower prices, the more traditional European component manufacturers lost significant market presence. During this period, in contrast to the near-universal marketing technique of introducing innovations on the expensive side of the marketplace and relying on consumer demand to emulate early adopters along with economy of scale to bring them into the mass market and SunTour introduced new technologies at the lowest end of the bicycle market, using lower cost and heavier and less durable materials and techniques, only moving them further upmarket if they established themselves in the lower market segments.
In the 1980–1983 period, Shimano introduced three groupsets with "AX" technology: Dura-Ace & 600, Adamas in the low-end. Features of these components include aerodynamic styling, centre-pull brakes, brake levers with concealed cables, ergonomic pedals. By 1985 Shimano introduced innovation only at the highest quality level trickled the technology down to lower product levels as it became proven and accepted. Innovations include index shifting, dual-pivot brakes, 8-9-10 speed drivetrains, the integration of shifters and brake levers; these components could only work properly when used with other Shimano components, e.g. its rear dérailleurs have to be used with the correct Shimano gear levers, cables and cassette. SunTour tried to catch up to this technological leap, but by the end of the 1980s SunTour had lost the technological and commercial battle and Shimano had achieved the status as the largest manufacturer of bicycle components in the world. Shimano's marketplace domination that developed in the 1990s led to the perception by some critics that Shimano had become a marketplace bully with monopolistic intentions.
This viewpoint was based on the fact that Shimano became oriented towards integrating all of their components with each other, with the result being that if any Shimano components were to be used the entire bike would need to be built from matching Shimano components. The alternative perspective is that by controlling the mix of components on the bicycle, a manufacturer such as Shimano can control how well their own product functions. Shimano's primary competitors make proprietary designs that limit the opportunity to mix and match componentry. In 2003 Shimano introduced "Dual Control" to mountain bikes, where the gear shift mechanism is integrated into the brake levers; this development was controversial, as the use of Dual Control integrated shifting for hydraulic disc brakes required using Shimano hydraulic disc brakes, locking competitors out of the premium end of the market. However, with their 2007 product line, Shimano moved back to making separate braking and shifting components available in addition to the integrated "Dual Control" components, a move to satisfy riders that wished to use Shimano shifting with other brands of disc brakes.
Shimano in 1990 introduced the Shimano Pedaling Dynamics range of clipless pedals and matching shoes designed so that the shoes could be used for walking. The shoes have a recess in the bottom of the sole for fitting the smaller cleats and therefore it does not protrude, while conventional clipless road pedals are designed for road cycling shoes which have smooth soles with large protruding cleats, which are awkward for walking; the SPD range, in addition to other off-road refinements, were designed to be used with treaded soles that more resemble rugged hiking boots. SPD pedals and shoes soon established themselves as the market standard in this sector, although many other manufacturers have developed alternatives which are arguably less prone to being clogged by mud and/or easier to adjust
The bicycle pedal is the part of a bicycle that the rider pushes with their foot to propel the bicycle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket spindle and propel the bicycle's wheels. A pedal consists of a spindle that threads into the end of the crank, a body on which the foot rest is attached, free to rotate on bearings with respect to the spindle. Pedals were attached to cranks connecting directly to the driven wheel; the safety bicycle, as it is known today, came into being when the pedals were attached to a crank driving a sprocket that transmitted power to the driven wheel by means of a roller chain. Just as bicycles come in many varieties, there are different types of pedals to support different types of cycling. Traditionally, platform pedals were pedals with a large flat area for the foot to rest on, in contrast to the quill pedal which had little surface area. One form of the platform pedal had a large flat top area and flat bottom for use with toe clips and toe straps.
They were designed for greater comfort. They had a smaller cutaway underside giving greater cornering clearance, needed for track cycling, they were marketed as being more aerodynamic than conventional quill pedals. Attaching the shoes to the pedals gives the user more control over the pedal movements. There are two methods for attaching a cyclist's shoes to their pedals: toe clips – a basket-and-strap device which hold the foot in place – and so-called clipless pedals, where specialized shoes with built-in bindings attach to compatible pedals. In mountain biking and BMX, platform pedals refer to any flat pedal without a cage. BMX riders use plastic pedals made of nylon, polycarbonate, or carbon reinforced plastic, although aluminum alloy, magnesium are not uncommon pedal body materials. Mountain bikers tend to use aluminum or magnesium because of the necessary use of metal studs to offer grip while the pedals are wet and slippery. BMXers tend to prefer platforms to cage pedals because they offer more support and grip for flexible "skate" shoes by using short metal studs.
Cage pedals are more popular in the low end mountain bike range. In general, cage pedals are uncommon in all types of biking, although there is a niche market within mountain biking. Platform pedals are available in a wide variety of types and prices, ranging from disposable plastic units used for test rides on new bicycles to high-end downhill models. Budget models may be made of steel or aluminum and incorporate reflectors for safer riding on streets at night, in addition to complying with some traffic laws. Less expensive platform pedals are considered disposable and cannot be rebuilt when worn out. More expensive platform pedals for the mountain bike market are available with replaceable metal traction pins and cartridge bearings. Lightweight pedals intended for Freeride and downhill cycling have been made from exotic metals such as magnesium. Toe clips are not installed on this type of pedal because they are considered unsafe by some MTB and BMX riders. In downhill racing, the extra power and grip offered by clipped pedals is utilized at the risk of clipped in crashing in which the bicycle can stay attached to the foot of the victim.
However, fixed gear riders have started using fabric straps instead. The quill pedal is a common pedal system on bicycles, it consists of a main axle section, attached to the bicycle crank arm and contains extensions from the axle to which parallel cage plates are attached at the front and rear of the pedal. In order to utilize the quill pedal, the cyclist pushes his foot against the platform formed by the parallel cage plates. To improve the performance of the quill pedal toe clips were added; the toe clip is a thin plastic attachment to the front cage of the pedal. The toe clip is shaped like the toe of a shoe and its function is to prevent a cyclist's shoe from slipping off the pedal during the forward pedaling motion. A further enhancement of the quill pedal was modifying the toe clip to allow a strap and buckle to go around or through both the pedal and the toe clip to encircle the cyclist's foot on the top of the pedal; this strap is made of leather or nylon. To further improve the quill pedal's efficiency a "cleat" was developed.
This cleat consists of plastic attachment to the cyclist's shoe. The cleat is adapted to engage a quill section of the bicycle pedal; the use of the slotted cleat enhances a cyclist's ability over that provided by toe clips and strap, enabling for greater pedaling efficiency. Although quill pedals can be used with smoothed-soled cycling shoes or ordinary shoes, they were designed to be used with cycling shoes which had a slotted shoeplate attached to its sole; the disadvantage with this system is that to remove the shoe from the pedal a rider had to reach down and loosen the strap by hand or leave the toe strap loose and thus give up some efficiency. This type of pedal and pedal setup was common for racing cyclists until the mid to late 1980s. Quill pedals are sometimes said to "pick up tab" on the rear of the pedal; the weight of the toe clip and strap would make the pedal hang upside down, the rider would tap the quill with their shoe to flip the pedal over so the shoe could be inserted into the pedal.
The main difference between track and touring quill pedals is width. Track pedals are narrow and the front and back plates of the cage are separate, road being a little wider with a one piece cage in a shape of a sideways "U", touring being the widest to allow for comfort when used with wider
Splines are ridges or teeth on a drive shaft that mesh with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them. For instance, a gear mounted on a shaft might use a male spline on the shaft that matches the female spline on the gear; the splines on the pictured drive shaft match with the female splines in the center of the clutch plate, while the smooth tip of the axle is supported in the pilot bearing in the flywheel. An alternative to splines is a key, though splines provide a longer fatigue life. There are several types of splines: Parallel key spline where the sides of the spaced grooves are parallel in both directions and axial. Involute spline where the sides of the spaced grooves are involute, as with an involute gear, but not as tall; the curves increase strength by decreasing stress concentrations. Crowned splines where the sides of the spaced grooves are involute, but the male teeth are modified to allow for misalignment. Serrations where the sides of the spaced grooves form a "V".
These are used on small-diameter shafts. Helical splines where the spaced grooves form a helix about the shaft; the sides may be involute. This can either minimize stress concentrations for a stationary joint under high load, or allow for rotary and linear motion between the parts. Ball splines where the "teeth" of the outer part are implemented with a ball bearing to allow for free linear motion under high torque. Drive shafts on vehicles and power take-offs use splines to transmit torque and rotation and allow for changes in length. Splines are used in several places on bicycles; the crank arm to BB shaft interfaces that are splined include ISIS Drive, Truvativ GXP and Howitzer, Shimano's Octalink and many others, most of which are proprietary. Some cranksets feature modular spiders. Cassettes engage the freehub via a spline that has one groove wider than the others to enforce a fixed orientation. Disc brake mounting interfaces that are splined include Centerlock, by Shimano. Aircraft engines may have a spline upon.
There may be a master spline, wider than the others, so that the propeller may go on at only one orientation, to maintain dynamic balance. This arrangement is found in larger engines, whereas smaller engines use a pattern of threaded fasteners instead. There are two types of splines and external. External splines may be broached, milled, rolled, ground or extruded. There are fewer methods available for manufacturing internal splines due to accessibility restrictions. Methods include those listed above with the exception of hobbing. With internal splines, the splined portion of the part may not have a through-hole, which precludes use of a pull / push broach or extrusion-type method. If the part is small it may be difficult to fit a milling or grinding tool into the area where the splines are machined. To prevent stress concentrations the ends of the splines are chamfered; such stress concentrations are a primary cause of failure in poorly designed splines. Hirth joint Keyed joint Reeding Coupling Robert Rich Robins.
"Tooth Engagement Evaluation of Involute Spline Couplings". Brigham Young University. Retrieved 2010-07-08