Pen (mechanical engineering)
Pins are simple machine elements by means of which workpieces to one another connected to. In this respect, they are comparable to nails , but they have neither heads nor points.
Pens exist in different designs and for different purposes e.g. B .:
- Cylindrical pins ( cylindrical shape),
- Taper pins ( cone shape),
- Dowel pins (slotted cylindrical sleeves),
-
Grooved pins (cylindrical with longitudinal notch ),
- Grooved pin (notch over entire length),
- Grooved pin (notch not over the entire length).
Two or more workpieces are positively connected to one another in the radial direction of the pins by means of a pin . The pin is inserted into a hole going through all parts. If the pin (cylindrical pins with oversize) is pressed into the hole ( press fit ), a force fit is created that prevents it from falling out. A dowel pin is elastically reduced in diameter when it is pressed in, which also creates a frictional connection. Although a grooved pin deforms the wall of the bore, it essentially holds in place through a force fit. Otherwise an additional measure is required. So z. B. a special pin - a bolt - prevented from falling out by transversely inserted pins ( split pins ). In order for a pressed-in pin to be dismantled, it must be possible to knock it out from the opposite side. A pressed-in pin can only be removed from a blind hole if it is specially designed (e.g. a cylindrical hollow pin with an additional internal thread ).
A pin is mostly stressed by a transverse force . A shear pin is a pin designed in such a way that it fails at a certain transverse force.
In addition to the usually rotationally fixed connections, pins are also used to produce rotatable connections between two parts (with additional measures to prevent them from falling out).
Standard information
- Example:
- Straight pin EN ISO 8734
- Designation: straight pin
- Standard: EN ISO 8734
- Shape or type: A
- Nominal diameter × nominal length (in millimeters): 4 × 20
- Material: steel
Pen types
There are suitable pens for different areas of application, which can be distinguished as follows:
Straight pin
Simple cylindrical shape with mostly rounded or beveled edges. This type of pin is used for connections and for fixing parts. The cylinder pin is used for connections which secure the position and which never or hardly need to be loosened. They are expensive to use because of the additional work step required to ensure sufficient borehole friction.
For fixed connections they are manufactured with tolerance m6, for loose connections with h8 or h11.
Standardized according to EN ISO 2338, formerly DIN 7 (unhardened) or EN ISO 8734, formerly DIN 6325 (hardened version).
Taper pin
Slight truncated cone shape (cone taper C = 1:50); Rounded end faces. With frequent dismantling and assembly, the bores widen over time. Taper pins can also be used after they have been widened, although the driving depth increases. Reaming the borehole to a conical shape and fitting the pin is relatively expensive.
Standardized according to EN 22339, formerly DIN 1 .
Tapered pins are also manufactured with threaded pins in accordance with DIN EN 28737 and used in blind bores.
Grooved pin
Notches are made in the circumference of the pin. These notches can have different shapes depending on the intended use (grooved pin, grooved taper pin, grooved taper pin, grooved cylindrical pin and grooved pin, see also EN ISO 8740… 8747). The notches give the notch pin a vibration-proof hold even in very smooth bores, which often remains even after dismantling and reuse. When used in blind holes, the grooves of the grooved pins allow the trapped air to escape.
Roll pin
Similar in effect to the grooved pin , the roll pin is a short sleeve made of spring steel . This is less robust, but easier to drive in, detach and reliably reuse. The longer version of a roll pin is the clamping sleeve.
calculation
The dimensioning or the proof of the load-bearing capacity of pin connections is carried out depending on the dominant stress through assessment
- the shear stress in the pin (shearing),
- the surface pressure between the pin and the bore (hole reveal) and / or
- the bending stress in the pin.
Individual evidence
- ^ A b c Alfred Böge, Wolfgang Böge: Handbook of mechanical engineering: Basics and applications of mechanical engineering , p. 811, Springer-Verlag
- ↑ http://www.tedata.com/2257.0.html