DFM DESIGN RULES • HOLE DISTORTION PREVENTION

Minimum Hole-to-Edge & Hole-to-Bend Sheet Metal Design Rules

Prevent hole ovalization and flange tearing during brake forming. Design standards specifying minimum clearance distances between laser-cut holes, internal cutouts, sheet edges, and press brake bend lines.

Min Hole Diameter 1.0 × T Thick Sheet Laser Limit

Min Hole-to-Edge 2.0 × T Prevents Edge Bulging

Min Hole-to-Bend 2.5 × T + R Prevents Teardrop Stretch

Relief Notch DEPTH > R Zero Flange Tearing

Fast-Track CAD Intake → View Machine Specifications Direct: (860) 410-1801

PLASTIC DEFORMATION DYNAMICS

Why Holes Distort Near Bend Tangents

During press brake bending, the sheet metal in the bend zone undergoes severe tensile stretching. If a hole or slot is placed too close to the bend radius tangent, material flows into the opening, resulting in an elongated teardrop shape or cracked fastener threads.

Rule 1: Hole-to-Bend Distance

Clearance Formula: $D_{min} = 2.5T + R$

The edge of any hole must be located at least $2.5$ times the sheet thickness ($T$) plus the inside bend radius ($R$) from the bend line tangent.

Rule 2: Minimum Hole Diameter

Diameter Formula: $Dia_{min} ge T$

Laser cutting or punching holes smaller than material thickness causes thermal blowouts or punch pin shear. For aluminum, maintain $Dia ge 1.0T$; for steel, $Dia ge 0.8T$.

Rule 3: Bend Relief Cutouts

Relief Notch: Width $ge T$, Depth $ge R$

When bending a partial flange, laser cut rectangular or teardrop corner reliefs past the bend tangent to prevent tearing the adjacent flat web.

TECHNICAL SPECIFICATIONS & COMPLIANCE

Frequently Asked Engineering Questions

Detailed answers regarding our Plainville facility capabilities, material certifications, testing protocols, and defense contract compliance.

Q: What can I do if my design requires a hole closer to the bend than 2.5T?

Fabtron can either laser cut a smaller pilot hole and ream it to size after brake forming, or cut an adjacent bend relief slot that relieves the tensile strain around the hole.

DIRECT EXECUTIVE ENGINEERING CONSULTATION

Ready to Discuss Your Fabrication Requirements?

Speak directly with Garret Maino and our Plainville manufacturing engineering staff. Upload drawings for immediate DFM analysis and quotation.

Submit CAD Drawings → Call Plant: (860) 410-1801