How To Calculate Regrinding Life of Thick Turret And Trumpf Tooling

Grind life is the maximum usable length that can be removed from a punch by sharpening. The size of the punch and the thickness of 

the material being punched are factors that affect grind life.The formula for grind life is:

Here is a breakdown of that calculation using your specific parameters, explained through the physical mechanics of the machine cycle.

1. Understanding "Straight Before Radius" (SBR)The SBR is the total length of the usable "business end" of your punch. It is the distance 

from the very tip of the punch back to the point where the tool begins to widen or radius into the body.You cannot grind past this point 

because if you do, the punch will no longer fit through the stripper or will create a hole larger/different than intended. Think of SBR as 

your total "raw material" reservoir.

2. The Calculation Logic To find your usable life, you must subtract the "Required Extension" from your SBR. The punch has to be long 

enough to pass through three distinct stages at the bottom of its stroke:

*Stripper Thickness: The punch must travel all the way through the metal plate that holds the sheet down.

*Material Thickness: The punch must pass entirely through the workpiece.

*Die Penetration: The punch must enter the die (usually by about 3mm) to ensure the "slug" is fully snapped off and pushed down to 

prevent slug pulling.The Detailed Formula：

Grind Life = SBR - (Material Thickness + Die Penetration + Stripper Thickness

3.Practical Example Breakdown Using the figures for a B Station punch (1 1/4") working in heavy 6.35mm plate: