Die Break Allowances

Die break is the fractured surface on the edge of the part that is formed as the part is separated from the strip. A key advantage to fineblanking is that this die break can be eliminated or greatly reduced.

       s = Material thickness
       h 1 = Smooth land in % of s (to the begin of die break)
       h 2 = Smooth land in % of s (to peak of die break)
       b = Width of peak. The max. width b must not be larger
              than the material thickness s. The sum of all b's
              must not be more than 10 % of the marked circumference.
         t = Die break approx. 1,5 % of s.
        E = Determines, that tear is permissible along the marked
               circumference.

Therefore, the ratio of smooth land to part thickness should be
determined and mentioned on the part drawing.

Smooth land: This is the smooth area of the sheared edge.

Die break: This is the area that shows breakage on the burr side of the edge.

I~ These are cracks parallel to the material.

Determination of Die Break Allowance:

Fineblanking produces smooth sheared edges, provided certain conditions
are met. The process can be made more economic if some die break and
tear are permissible.