Shafts

Clad ends of thick boards

Shafts or scarf joint is a method that a plurality of workpieces to be joined together. Even in prehistory and early history , parts were connected by shafts to tools or weapons . The shaft makes a device “more handy”.

In modern connection technology , shafts in the narrower sense mean that two parts to be connected are beveled at the respective contact surface at an acute angle .

Shafts in wood

Finished stock. The inclined cutting creates a much larger contact area.

In a shanked wood connection , two elongated wooden parts ( rod , bar , other sawn timber ) are firmly connected to form a longer piece, resulting in a load-bearing, fiber-parallel longitudinal joint (DIN 1052-1 and 1052-2). The ends of the parts to be connected are bevelled, in this case the slope of the adhesive surface (ratio of connection length to component thickness or height) must not exceed ( ). ${\ displaystyle {\ tfrac {10} {1}}}$ ${\ displaystyle l / h \ leq 10/1}$

Adhesive surface inclination for a scarf. The ratio of the connection length to the component height must not be greater than . The rule of thumb is assumed.

{\ displaystyle l}

{\ displaystyle h}

{\ displaystyle 10/1}

{\ displaystyle l = 8h}

The inclined surfaces are placed on top of one another and glued .

If the rule is observed, the inclined contact surface is at most a little over ten times larger (exactly:) than the front surface before . The connection is also stronger because the wood fibers are glued together lengthways over a short distance and not just butt against each other. ${\ displaystyle {\ tfrac {l} {h}} \ leq {\ tfrac {10} {1}}}$ ${\ displaystyle {\ sqrt {101}}}$

If the piece is to be bent after joining, an even rounding is to be achieved with shafts, since the bending stiffness of the piece does not change abruptly over a very short distance, as is the case with a butt joint and, to a limited extent , with overlapping . When overlapping, the flexural rigidity changes abruptly at two joints. (It is sometimes referred to as a scarf when used to lengthen.)

Metal shafts

Also, sheets may be joined together by shafts and gluing or soldering. They are also bevelled (shanked) at their edges.

Shafts in fiber composite materials

The method of stocking is also used when gluing laminates. When two laminates are glued overlapping, peeling stresses arise at the edge of the adhesive surfaces. These tensions act perpendicular to the adhesive surface and detach the adhesive partners from one another under tensile load. With the method of stocking, the stiffness of the laminate to the edge of the adhesive surface is reduced by reducing the thickness in the overlapping area. The consequence of this is that the peeling stresses are also minimized and thus the strength of the bond is increased.

literature

Helmuth Neuhaus : Timber Engineering , Verlag Springer, 2009, ISBN 3519152487 , p. 136 f.

Individual evidence

^ Helmut Neuhaus: Timber engineering . Basics - dimensioning - verifications - examples. 3. Edition. Vieweg + Teubner Verlag, 2010, ISBN 978-3-8348-1286-5 , pp. 660 .
^ Ekbert Hering , Karl-Heinz Modler : Basic knowledge of the engineer , Hanser-Verlag, 2007, ISBN 3446228144 , p. 391
↑ Pahl / Beitz Konstruktionslehre: Methods and Application of Successful Product Development, Edition 8 Jörg Feldhusen , Karl-Heinrich Grote - October 18, 2013 Springer-Verlag - Verlag

[1] Helmut Neuhaus: Timber engineering . Basics - dimensioning - verifications - examples. 3. Edition. Vieweg + Teubner Verlag, 2010, ISBN 978-3-8348-1286-5 , pp. 660 .

[2] Ekbert Hering , Karl-Heinz Modler : Basic knowledge of the engineer , Hanser-Verlag, 2007, ISBN 3446228144 , p. 391

[3] Pahl / Beitz Konstruktionslehre: Methods and Application of Successful Product Development, Edition 8 Jörg Feldhusen , Karl-Heinrich Grote - October 18, 2013 Springer-Verlag - Verlag