The level of smoothness of a surface plays an important role in planning a
machine component, especially regarding the issues of friction, lubrication,
wear and resistance to fatigue. To produce an object with a good level of
roughness, a work process using good quality tools, accuracy and a high level
of precision is required. This results in components that are wear-resistant
and resistant to fatigue. The type of research used in this research is
experimental research (true experiment research), with a quantitative
approach. This research aims to explain the influence of one variable on other
variables. The dependent variable in this research is the surface roughness
value (Y), while the independent variables are cutting depth (X1) and rotation
speed (X2). The research results show that The average surface roughness
value at a depth of 1 mm is 53.33 µm, at a depth of 2 mm 83.33 µm and at a
depth of 3 mm 108.33 µm, so that the deeper the digging, the greater the
surface roughness value, or it can be said to be greater. rough workpiece
surface S45C. Furthermore, the spindle rotation speed influences the surface
roughness value, this can be proven by the average surface roughness value
at a speed of 800 RPM of 74.44 µm and at a speed of 600 RPM it is 88.33
µm, the faster the spindle rotation, the smaller the surface roughness value or
the smoother a surface, with constant feeding depth variation.