Spindle fibers attach to chromosomes during the metaphase of mitosis. The spindle fibers are formed in the beginning of metaphase.
Parallel fibers appear once the metaphase starts, and these are known as spindle fibers. The fibers attach to the centromeres of each chromosome. The spindle fibers make the chromosomes form into a tight kind of circle that surrounds the circumference of the spindle apparatus. There is an invisible line at which the chromosomes are aligned, that is called the metaphase plate. It is equidistant from the centrioles that are located on opposite sides of the cell. It is at this point that the chromosomes are ready to split their centromeres. Also, the chromatids will be made ready to separate at this time.