Magnetic disc apparatus

In a magnetic disc apparatus including a magnetic recording disc having at least two tracks formed thereon and a magnetic head assembly comprising a rotary shaft, an actuator arm connected to said rotary shaft, said actuator arm having a longitudinal axis intersecting the center of said rotary shaft, elongated suspension arms mounted on said actuator arm and magnetic heads, each of which is mounted on one end of said suspension arms, respectively, for magnetic recording and reproducing on said disc,

• one of said suspension arms comprising a reference suspension arm mounted on one end of said actuator arm and extending parallel to the axis of said actuator arm, and one of said suspension arms being mounted on the one end of said actuator arm at a mounting distance from and extending at an acute mounting angle relative to said reference suspension arm, said suspension arms having equal length and being made of the same material, and at least one of said actuator arm and said magnetic disc being made of a different material,
• the method of determining the mounting distance and angle by applying the following equations:
• .theta.=Sin.sup.-1 (Ka-Kd) ld/(Ka-Ks)ls
• la=Kd-Ks/Ka-Ks ld
• where
• Ka, Kd, and Ks are thermal expansion coefficients of the materials of said actuator arm, said magnetic recording disc, and said suspensions arms, respectively,
• ld is the distance between the magnetic head mounted on said reference suspension arm and the magnetic head mounted on said one suspension arm, and
• ls is the length of said suspension arms.