Fine blanking uses a supported workpiece, close tool guidance and compressive forces to produce a clean sheared edge. Punch-to-die clearance is one of the process variables, but a value that worked for a particular coupon is not a universal design rule. This reference reports three clearances tested in a published copper-alloy study using 2.5 mm sheet. It is useful for understanding the scale of the experiment and comparing its test levels. It is not a production recommendation for a different alloy, thickness, contour or press.

Fine Blanking Punch and Die Clearance

The source reports clearances of 0.0125, 0.025 and 0.0375 mm for 2.5 mm copper-alloy sheet. These correspond to 0.5%, 1.0% and 1.5% of the sheet thickness. The dataset labels the values as the study’s clearance variable, u. Confirm whether a tool drawing defines clearance per side or as a total diametral difference before using any number in a layout.

What the percentages mean

For a clearance percentage c% and sheet thickness t, the corresponding dimensional value is c × t / 100. For example, 1% of 2.5 mm equals 0.025 mm. The calculation is only a unit conversion. It does not say whether the process will meet an edge-quality target, nor does it identify the correct punch or die dimension for a particular blank. The blanking or piercing direction and which dimension controls the finished part also affect how the tool is sized.

The study varied clearance to evaluate its effect on the fine-blanked copper alloy. Its chosen percentages belong to that research setup. Other published investigations and production applications can use different clearance values because work material, thickness, contour, edge radii, V-ring geometry, counterpressure, tool wear and press stiffness influence the cut. Do not combine a percentage from one paper with dimensions from a different experiment and call the result a validated tool design.

How engineers use clearance data

In a development trial, an engineer may use a published clearance range to choose a small experimental matrix, then measure the resulting sheared zone, rollover, burr and dimensional consistency. The comparison should hold other conditions steady where possible, including material batch, thickness, punch and die condition, lubrication, clamping and press settings. A trial can reveal how sensitive a particular part is to clearance, but it cannot certify unrelated geometries.

Clearance also interacts with tool wear. A new or reground punch may behave differently from a worn edge, and a small change can alter contact, surface quality and tool loading. For complex contours, inside and outside features may have different local requirements. Record the measurement method and uncertainty because the listed clearances are measured in hundredths of a millimeter or less.

Do not treat the table as a setup sheet

The listed values do not include a complete die design, material shear strength, force capacity, blank-holder pressure, V-ring dimensions, punch guide clearance, die clearance convention or a target tolerance. The paper also concerns a specific copper-alloy sheet experiment. It cannot establish settings for steel, stainless steel or aluminum. Production engineering should rely on the material supplier, press and tooling supplier, validated process trials, and the part’s actual acceptance criteria.

Clearance is not the same as edge distance, punch diameter, die opening, bend allowance or tool-guide clearance. A dimensional mistake can create a collision or scrap tooling. Check the finished-part dimension chain and define the reference edge before calculating punch and die sizes.

Source

Experimental levels are from Liu et al., “Numerical simulation and optimization of fine-blanking process for copper alloy sheet,” in the International Journal of Advanced Manufacturing Technology. The paper reports 2.5 mm sheet and clearances of 0.0125, 0.025 and 0.0375 mm. The values are presented here as study conditions, not as general recommendations.