Tight-Tolerance Sheet Metal | Per-Feature Tolerance

Tolerances by feature

Unlike a machined block where one setup controls most dimensions, a formed sheet-metal part accumulates variation from cutting, bending, welding and assembly. That is why we separate tolerances by feature type rather than quoting a single blanket number. The values below are typical reference starting points — the value that applies to your part is confirmed during quotation against the drawing.

Precision laser cutting & hole position

Laser cutting is the most repeatable step in sheet-metal work, which makes it the right place to locate features that mate with other parts. We control kerf compensation, lead-in position and micro-joints so profiles stay true to the programmed geometry, and we tab or nest small parts to avoid edge burn on fine details.

• Edge quality: ISO 9013 defines cut-quality classes by underside drag and roughness; we select a class that matches the part’s function.
• Hole position: pierced holes are located relative to cut datum edges; for holes that must sit in a machined bore later, we leave stock and finish them on a CNC mill.
• Heat affect: on thin or reflective materials we tune power and speed to limit the heat-affected zone that can disturb subsequent bending.

For buyers comparing shops: ask whether the quoted tolerance applies to the cut feature or to the finished, bent part. Those are different numbers, and conflating them is the most common source of fit problems downstream.

Precision bending & forming

Bending is where sheet metal earns its shape — and where tolerance discipline matters most. A bend is not a single dimension; it is angle, leg length, bend radius and orientation, all interacting. We manage:

• Bend-to-edge and hole-to-bend: distance from a bend to a feature shifts as the part forms; we account for this in the flat pattern so the finished location lands in tolerance.
• Minimum bend radius: set by material and thickness to avoid cracking, especially on aluminum and high-strength steel.
• Twist and bow: long legs and asymmetric parts are checked for distortion and corrected with tooling or restrike.

Welding, distortion & assembly

Welding introduces heat, and heat moves metal. For tight-tolerance assemblies the job is to keep that movement predictable and then remove what remains. Our approach:

• Weld sequence & fixturing: joints are planned and clamped so contraction pulls the part toward, not away from, true.
• Tack strategy: tack pattern and size are chosen to control movement before the full weld.
• Post-weld recovery: where a bore, face or mating edge must be tight, we machine it after welding rather than hoping the weld held the dimension.
• Straightness & flatness: checked against ISO 13920 classes selected to match the assembly’s function.

GD&T & tolerance stack-up

Two parts can carry the same ±0.1 mm note and behave completely differently — because tolerance stack-up decides whether the accumulated variation still fits. We read your drawing’s feature-control frames and build to them:

• Datums: we establish the primary–secondary–tertiary scheme your drawing calls out, so every measurement references the same faces.
• Position & profile: true-position and profile controls let a feature float within a zone, which is often the right model for formed parts.
• Stack-up review: on assemblies we check whether the sum of individual tolerances leaves enough clearance, and flag it before production rather than at incoming inspection.

Materials

Material choice drives how tightly a part can be held and how it behaves after forming:

See the full materials overview for grades, available forms and notes on plating and powder coating.

Sheet metal + CNC secondary machining

Forming is fast and cheap for shape; machining is precise for features. Combining them is often the most cost-effective route to a tight-tolerance part:

• Tight bores in a bent bracket: cut a pilot, bend, then bore to final size so the hole is true after forming.
• Mating faces and channels: mill flat seats or slots that the brake cannot produce.
• Threads and reamed holes: added after forming to avoid distortion.

For parts that are predominantly machined but include formed features, compare with our tight-tolerance CNC machining capability — the right process mix depends on which features are critical.

Quality inspection & dimensional verification

“Tight” is only real if it is measured. Our inspection scales with the part:

• First-article inspection (FAI): the first part off the line is fully checked and used to lock the process.
• In-process checks: bend angle, hole position and flatness sampled during the run.
• CMM reporting: for critical geometry we produce a dimensional report tied to your datums.
• Traceability: material certs and process records kept under ISO 9001:2015.

Products & applications

Prototype to production

The same drawing drives both prototype and production, so what you validate is what you get:

• Prototype: 1-piece sampling to confirm fit, bend strategy and any hybrid machining.
• Low volume: flexible runs for pre-production and spares.
• Production: repeatable setups with in-process checks and FAI on new lots.

Learn how formed parts sit alongside our broader sheet metal fabrication services.

Case studies