الفهرس 
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Abstract
Fatigue life of is one of the most required specifications for machined components. There are various machining parameters which have an effect on fatigue life. In this investigation, the effect of these parameters (cutting speed, cutting depth, feed rate, and tool nose radius) on surface roughness and on fatigue life of 0.12% carbon steel components is investigated. For this purpose, steel specimens were machined on a CNC lathe and then subjected to four points bending fatigue test. These specimens were machined using different cutting speeds, different feed rates, different depth of cut, and different tools nose radius.
Measurements of surface finish were carried out for all machined specimens before fatigue test. The fatigue tests were carried out using Four-point rotating bending test .A machine was designed and constructed especially for the purpose of this investigation. This type of machine is used to produce a constant bending moment along the specimen’s length. The results of investigation show that, there is a great dependence of the fatigue life of machined components on the cutting conditions used during turning. Each machining parameter has different influence on fatigue life. The results showed also that there is an interaction between the different machining parameters (conditions) on the effect on fatigue life. The surface finish is obtained after machining has a great influence on fatigue life. The results also show that, the longest fatigue life can be obtained with a specimen machined by applying such cutting speed at 25.13 m/min., low feed rate (0.1 to 0.2 mm/rev.), small depth of cut (0.1 to 0.15 mm.) and insert with nose radius 0.4mm.