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MATERIAL SELECTION FOR SHAFT & KEY 1

SHAFT A shaft is a common and important machine element. It is a rotating member, in general has a circular cross section and is used to transmit power.  The shaft maybe hollow or solid.  The shaft is ed on bearings and it rotates a set of gears or pulleys for the purpose of power transmission.  The shaft is generally acted upon by bending moment, torsion and axial force. 

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The material used for ordinary shafts is mild steel.  When high strengh is required, an alloy steel such a nickel, nickel_chromium or chromiumvanadium steel is used.  Shafts are generally formed by hot rolling and finished to size by cold drawing or turning and grinding. 

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Shafts can be made from low carbon, cold-drawn or hotrolled steel, such as ANSI 1020-1050 steels. A good practice is to start with an inexpensive, low or medium carbon steel for the first time through the design calculations. Typical alloy steels for heat treatment include ANSI 134050, 3140-50, 4140, 4340, 5140, and 8650. Typical material choices for surface hardening include carburizing grades of ANSI 1020, 4320, 4820 and 8620. Cast iron may be specified if the production quantity is high, and the gears are to be integrally cast with the shaft.

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KEY 

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A key is a machine element used to connect a rotating machine element to a shaft.The stresses induced in key shaft is same as that of shaft or hub. So, the material used in key should be same as that of shaft to avoid failures due to overload. Key stress equals shaft stress when the key length is 1.6 times the shaft diameter. 5

But modern coupling, particularly those made from alloy steels have shorter hubs than this.  They are usually equal to or only slightly longer than the shaft diameter.  In this case, key stress is about 50% higher than shaft stress.  This would appear to require that the key material be 50% stronger than that of the hub; however, because part of the torque is transmitted through friction between the shaft and hub bore, the key material need only be as strong as shaft material. 

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Keys are usually made of steels or stainless steel and plated with zinc for wear and oxidation resistance.

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SCREW JACK 

A screw jack is a portable device consisting of a screw mechanism used to raise or lower the load.

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DESIGN OF HANDLE FOR SCREW JACK

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APPLICATIONS OF SCREW JACK                

Paper, press, printing industry Gypsum factories Sheet metal forming machinery Mechanical lifting applications Platform lifting applications Food processing machinery Construction sector Bridge jacks for road and bridge lifting Shipyards Opening and closing of penstocks  Industrial process Roll form machinery Mining industry Defence industry Lift tables Stage setup applications

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THANK YOU!!!

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