What are die marks in sheet metal bending?

The tooling used in press brakes will often leave a surface mark on the bent sheet metal. These marks are called die marks, die lines, or witness marks, and while difficult to prevent, there are a few things you can do to hide or eliminate the unwanted markings. 

SendCutSend does not offer die protection or mark removal, but one of the things you can do to minimize the effect the tooling has on your part is choose a harder material, such as stainless steel. The die marks on stainless steel won’t be as deep as on softer materials, and can be more easily removed or hidden. To blend out the die marks on your part, a dual action (DA) orbital sander works best.

Be sure to read our bending guidelines before you get started designing your part for our online bending service.

In Summary

What are die marks in sheet metal bending?

The tooling used in press brakes will often leave a surface mark on the bent sheet metal. These marks are called die marks, die lines, or witness marks, and while difficult to prevent, there are a few things you can do to hide or eliminate the unwanted markings. 

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We proudly use hardware by PEM

Flush Standoff, 4-40, .250" Zinc plus Clear Chromate

Aluminum: 5052, 6061, 7075 Steel: Mild, G30

SKUSO-440-8
Thread Size4-40 x .250″
Hole size in sheet (+0.003/-.0.000).168″
Minimum sheet thickness0.040″
Maximum sheet thickness.125″
Fastener materialSteel
Minimum distance hole C/L to edge0.230″
When determining the distance between two or more fasteners, you can calculate the distance by the formula, C/L to edge + 1/2 the diameter of the second mounting hole..345″
Recommended panel materialSteel/Aluminum
Coating typeZinc
Length.250″
Aluminum material ranges (5052, 6061, 7075)0.040″-0.125″
Steel material ranges (CRS, HRPO, HR)0.048″-0.119″

We proudly use hardware by PEM

Flush Standoff, 4-40, .250" Passivated

Stainless Steel: 304, 316

SKUSO4-440-8
Thread Size440
Hole size in sheet (+0.003/-.0.000).166″
Minimum sheet thickness0.04″
Maximum sheet thickness.125″
Fastener material400 Stainless Steel
Minimum distance hole C/L to edge0.230″
When determining the distance between two or more fasteners, you can calculate the distance by the formula, C/L to edge + 1/2 the diameter of the second mounting hole. Example shown with x2 of the same hardware..313″
Recommended panel materialStainless Steel
Coating typePassivated
Length.250″
304 Stainless Steel material ranges0.048″-0.125″
316 Stainless Steel material ranges0.060″-0.125″