Definition
Sheet metal fabrication forms flat metal stock into a part through cutting, bending and sometimes joining, rather than removing material from a solid block.
What it means for the calculation
Cost drivers differ from machining: bend lines, sheet thickness and the punch or nest pattern dominate, not removed volume.
Where it appears on the drawing
Shown as a flat pattern with bend lines and bend angles, plus a material thickness callout, rather than a solid 3D block with removed features.
Common mistakes
Applying machining-style tolerance thinking to bend angles and flat-pattern dimensions, which behave differently (springback, bend allowance). Also forgetting that bend order can affect which features are still reachable.
Cost drivers differ from machining: bend lines, sheet thickness and the punch or nest pattern dominate, not removed volume.
See how Blake reviews a partFrequently asked questions
How is sheet metal different from milling?
Sheet metal starts from a flat sheet and is bent and cut, not machined from a solid block.
What is bend allowance?
An adjustment to the flat-pattern length that accounts for how the material stretches around a bend.
Does sheet metal thickness affect tolerance?
Yes, thicker material generally needs a larger minimum bend radius and can affect achievable flatness after forming.