Long hole
In technology, an elongated hole denotes an elongated bore or groove . Its narrow sides are closed off by semicircles, the diameter of which corresponds to the width of the elongated hole. The long sides of the elongated hole run parallel to each other.
production
Elongated holes can be made in the following ways:
- Milling using a slot cutter
- Punching with a suitable punching tool
- Drilling , subsequently routed the space between the edge of bores with endmills
- Insertion in the tool as a mold for cast parts
- Burning out using an acetylene-oxygen cutting torch or plasma cutter
- Laser cutting , water jet cutting , etc. Ä.
Applications
The elongated hole works like a pair of rails, so it is a kind of " guide element " within which z. B. screws are inserted to fix machine parts (e.g. two metal plates) adjustable to each other. This z. B. tolerances are compensated.
In steel construction , elongated holes are used in structural steel structural components that are mainly subjected to static loads to compensate for tolerances and to facilitate assembly. The use is regulated in Eurocode 3 section 1–8 ( EN 1993-1-8 Dimensioning and construction of steel structures - Part 1-8: Dimensioning of connections ), the dimensioning of components is complex. In the case of screws loaded in the screw axis direction (normal force) and screws loaded perpendicular to the screw direction in the longitudinal direction of the elongated hole, corresponding shims with the same material as the base material and a thickness of more than four millimeters must be used to ensure the frictional connection through clamping forces. If necessary, such washers must also be welded to the base material (not the screw).
The use of elongated holes for screw connections in dynamically loaded components such as machine foundations, generator tables and especially on crane runways is not possible due to the notch effect and the lack of positional security. In connection structures such as crane runway consoles, elongated holes are used as assembly compensation. Punched elongated holes are unfavorable for dynamically loaded parts (cracks and local material embrittlement due to hardening during shear ).
The holder of an alternator , which is to be attached to the engine block , usually consists of a normal, round hole and an elongated hole. While the round hole on the alternator bracket does not allow any tolerances, i.e. it can only be fastened in a certain position to the counterbore on the engine block, the other hole on the alternator is designed as an elongated hole. This enables easier insertion despite the V-belt on the engine block already being pulled on. It also functions as a tensioning element, because the screw fixing can be attached anywhere along the length of the elongated hole. When the belt tension is reached, the alternator is fixed in the elongated hole by tightening the screw.
In addition, elongated holes are used in moving structures such as crank loops .
Individual evidence
- ^ A. Widmaier in Lueger: Lexicon of the whole technology and its auxiliary sciences , 2nd edition 1904-1920, Vol. 6 Stuttgart, Leipzig 1908., p. 69, [1]
- ↑ Bernd Wittchen, Elmar Josten, Thomas Reiche: Holzfachkunde: A teaching, learning and work book for carpenters / joiners, wood mechanics and specialists for furniture, kitchen and moving services . Vieweg + Teubner, December 11, 2008, ISBN 978-3-8348-0530-0 , p. 201 (accessed on January 2, 2012).
- ↑ Wilfried König, Fritz Klocke: Manufacturing process 5: Sheet metal forming . Springer, April 1, 1997, ISBN 978-3-540-62348-9 , p. 236 (accessed January 2, 2012).