| I now it still like today, see it
still exact before me: The chaos in that drawer in the parental hobby
cellar, on which in fat letters " SCREWS " to be read is.
Heavily, this accommodated some kilograms a drawer the entire screw
supply of a family, which - the reader perhaps already noticed it - with
the work particularly much at the hat did not have. For thickness and
thin screws, be enough and short screws, between them innumerable
different nuts/mothers and wearing parts - simply everything in
disorder. Then really once if something had to be bolted, then the
search maneuver lasted usually substantially longer, than the actual
work.
Who believes now, the describing is an individual case, which errs. Hardly a property is as carelessly treated, as those inconspicuous metal parts, which on lives and death, on desire or grind to often decide. The number of bolted connections at a motorcycle is usually difficult to understand high. Who always gives its vehicle to the workshop, is fine. Who creates however even hand, for that it is advisable, once fundamentally with the topic to concern itself - perhaps this article can be an entrance. Begun the history of the thread said quite early, more exactly, already in the antiquity (250 v. Chr.) with the " Archimedean screw ", which served essentially to carry water of a low water level on are situated more highly. Wine and oil guns were described already with Plinius, the oldest well-known recordings originate from that 16. Century of Leonardo da Vinci, but it should last still another whole time, until the screw in today's form revolutionized the technique. Became long time screws and the fitting threads in manual work piece for piece (and thus always differently - thus in each case a screw fit a nut/mother!) manufactured, a technician made itself named Joseph Whitworth thought over the standardisation of threads, tolerances, materials and fits in the England of the early industrialization phase. It was convinced of the fact that it was for flourishing mechanical engineering from indispensable necessity to create an exchangeability of individual components and this is evenly only with a standardisation of the universally necessary components as, for example of the screws, possible. one indicates 1841 today as the " invention year " of the standardized thread by Whitworth, which carries still today the name of its inventor. Philosophy Whitworths was it to determine that Masze of a screw which are responsible for later fitting in a thread. Fast the factors were clear: Thread diameter, minor diameter, angle of pressure and upward gradient. For the first time it was now possible to install components, which were prefabricated at place A, at place B. Also a spare part production became thus possible. Due to the initially strong dominance of English mechanical engineering the English Whitworth thread, which was based on the English inch unit, spread rapidly also over the remaining europe out. And this, although derived on the mainland since the conference of meter 1875 the meter (Urmeter in Paris) was actually determined and thus from it a metric thread regulation finally as measure of the things. Which followed, a for many years was next to each other and against each other the different thread measure, because also the United States of America had created in the meantime again own measure (" ASME: American Society OF Mechanical Engineers " and " SAE: Society OF of automotives Engineers ") - the confusion was thus complete. A certain standardisation could to be caused be able in the subsequent years at least within the three main groups - it gave now per group (English inch; amerik. inch; metrically) only a system - basically in this muddled situation however to today only few changed. Owner of a Harley, equal which year of construction, may themselves about the inch thread of American provenance please, while owners of classical British Bikes are busy exclusively with inch tool of English origin, and to which remainder of the motorcycle world with metric screws may take favourite. Who possesses several motorcycles from different manufacturing countries, thus pitch can have and its workshop directly three-way equip. If one wants to measure now those, at that time from Whitworth of postulated regulation features of a screw, then one needs for it only in principle one caliper gauge, which should possess both a metric as well as an inch organization, a screw gauge (again metric and inch) and some tables of dimension, in order to find the suitable DIN standard or designation out of the available screw if necessary. With the caliper gauge parallel to the external thread of the thread measure one determines. If it amounts to for example 10 millimeters, then one has to do it with a screw with the diameter M 10, whereby the M is for metric. M 6, M 8, M 10 and also M 12 are usual sizes in the building of motorcycles and should thus (best in different lengths) in no assortment be missing. Next ratio is the upward gradient. This is measured with metric threads the distance between two threads, in each case from point to point. For exact regulation a screw gauge should to assistance taken. With the inch threads from England one calls the upward gradient number of threads, which is also somewhat differently determined. The number of threads indicates the number of threads, which one can count on an inch. In the plain text: An inch screw with the number of threads 12 needs thus 12 revolutions, in order to deep-close itself an inch. The outside diameter of the thread is naturally likewise indicated in inch. Also in this system there are to rule and fine threads, the designations reads " BSW - British standard Whitworth " and " BSF - British standard Fine Thread Whitworth ". Likewise the Americans cook their own Soup. Also in the country of the unlimited possibilities that is inch considerably, also the determination of the number of threads is identical to the British system. The reason, why one may not throw English and American inch threads nevertheless into a pot, is a different angle of pressure. While English inch threads possess an angle of pressure of 55 degrees, American threads have an angle of pressure of 60 degrees - they are thus not among themselves exchangeable. " UNC - Unified Coarse Thread " and " UNF - Unified Fine Thread " are the names for American rule and fine thread. Apart from the usual thread types specified above there are still innumerable special forms, which can meet a ambitionierten nut runner also quite once. Even gasoline and oil lines indicate often conical special thread, which show a better sealing behavior. Also owners of older English motorcycles must make friends themselves with Exotics. Those come not rarely " BSCy threads " under (British standard Cycle), which are to be found main at spokes, chains tension adjusters and engine parts. BSCy threads have always the same number of threads of 26, whereby 9/16 inch and 5/8 inch can indicate alternatively also 20 courses per inch. Apart from the almost inexhaustible area of the thread types, one should still lose a few words over materials and firmness, nuts/mothers as well as over forms of the screw head and wrench sizes. But always in sequence. As the most usual screw material steel becomes related. In order to be assigned to the rust not immediately, screws are usually galvanized. Depending upon quality of the used steel there are different strength classes, which are readable on the screw also. In order to be able to interpret the indicated value correct, one must concern oneself briefly with the characteristics of steel: If one attracts the nut/mother of a strutted steel screw slowly ever fixed, then the resistance constantly grows, the screw lengthens itself slightly. Since steel possesses however a certain elasticity, the screw diminishes like a rubber band after the solve again together. This functions however only up to a certain limit. If this is exceeded, then the screw lengthens itself lasting. The optimal firmness of a screw connection is achieved, if one tightens the screw so firmly that they " recover themselves " in extension area find. And evenly over these firmness areas the inscription on a screw gives information. There two numbers separated by one point are to be read. The first number indicates the minimum tensile strength, second the relation of the minimum yield strength to the minimum tensile strength. An example makes it clear: It is to be read on a screw 8,8 then means the eight before the point that this screw possesses a tensile strength of 800 N/mm, afterwards tears it off. The second number indicates, starting from which traction power the screw lengthened itself so strongly that it does not pull together again. The calculation occurs according to the following pattern: Assumed, the screw is marked by 10.9, then the tensile strength amounts to thus 1,000 N/mm. The elongation limit are those 1,000 N/mm x 0,9 (thus 90% of the tensile strength), thus 900 N/mm. These values have to do however nothing with the torques, which are to be adjusted on a torque wrench. This to calculate, requires a larger expenditure and depends not least on the material which can be bolted. Each hobby nut runner does thus well to procure itself the torques from a repair manual in order to avoid damage to screws and threads. Who would like to exchange screws at its vehicle thus in the future, sometimes should absolutely to the firmness specification pay attention, cheap department store screws can expensive damage to the consequence have (importantly: Also the use of screws also to high firmness can cause damage!). Beside screws from steel also such are applicable from aluminum, high-grade steel (VA) or titanium. The latters are expensive to use first mentioned only in basic screw connections and such from VA in many fields of application problematic (VA possesses substantially smaller extension characteristics than steel!). Who plans the application of such " Exotics", should by a specialist leave itself advised, in order to avoid unbill. If one must penetrate with the views over firmness and thread deeply into the realm of the engineer art, then the handling of the different head forms of a screw is to a very large extent matter of taste. Simplified said: Is permitted, what pleases! No matter whether female hexagon -, slot -, cross slot -, hexagonal or other head form, from technical control room regarded hardly plays this a role. Often one has however hardly the possibility for the selection, since the space conditions make a certain head form necessary. If one has now finally the field of application appropriate screw in the fingers, then the actual ATS of bolting begins. At the latest now one should think about wearing parts, nuts/mothers and suitable wrenches. The nut/mother and disk question are fast clarified: Ever one is always well served a disk under nut/mother and screw head, thus. Who has special fear of the lot vibrating of the nut/mother, can fall back to lock washers, spring washers or toothed washers. In any case ones to recommend are so-called stop nuts/mothers, that have an integrated nylon ring to the protection against the lot vibrating. Even extremely vibrating motorcycles will break off themselves to it the teeth. In the end still a few words to the different sizes of the wrenches for hexagonal cuts back. If the allocation of the metric is and American inch thread simple to the suitable wrench widths still, then there is again once the British, who provide for confusion. They have two systems of units, which are to be read off also both on the wrench. In contrast to the American inch tool the Englishmen indicate not the muzzle width, but to the threads diameters as base factor. Since in the course of the time however the heading size for the same thread was reduced, two specification is necessary. The instruction " 3/8 W 7/16 BS " means thus that this code for 3/8 inch thread of the old system with large heading (w) as well as for 7/16 inch thread of the new system with small heading (BS) fits. Whom the heading smokes now, which does not have to despair. It is still no expert of the sky pleases - over the stage of the " module loading principle " the reader of this article is in any case away. (Quelle: "Thunder Cycles") |
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