Fabrication Tolerances
Standard tolerances for structural steel rolling, bending, cutting, and threading at Pacific Roll LLC. Reference data for engineers, detailers, and project managers. Tighter tolerances available on request — contact us to discuss your project requirements.
Share on LinkedInBeam Rolling & Cambering
Wide flange, S-shapes, and HP sections rolled to a radius or cambered to a specified mid-ordinate. Tolerances follow AISC Design Guide 33 and ASTM A6 sweep/camber allowances.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Radius (arc length ≤ 20 ft) | ± ³⁄₁₆" | Measured at centerline of section |
| Radius (arc length > 20 ft) | ± ¼" | Measured at centerline of section |
| Camber mid-ordinate | ± ³⁄₁₆" or ± 3%, whichever is greater | Per AISC DG33 §3.4 |
| Sweep (weak-axis bow) | ± ³⁄₁₆" per 10 ft | Cumulative over full length |
| End squareness | ± 1/16" per inch of depth | After rolling; trim cuts available |
| Twist | 1° per 10 ft | Measured with section on flat surface |
Tighter tolerances available on request for architecturally exposed structural steel (AESS).
Angle Rolling
Structural angles rolled the easy way (leg out) or hard way (leg in). Distortion of the legs is inherent to the process; specify acceptable leg flatness if critical.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Radius tolerance | ± ¼" | Centerline of angle |
| Leg flatness (easy way) | ± 3/16" per foot of leg | Outer leg may bow slightly |
| Leg flatness (hard way) | ± ¼" per foot of leg | Inner leg compression; more distortion expected |
| Twist | 1.5° per 10 ft | |
| End squareness | ± 1/8" |
Tube Rolling
HSS square, rectangular, and round tube bent to radius. Ovality and wall thinning are inherent; mandrel bending is available for tighter ovality requirements.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Bend radius | ± 3/16" | Centerline radius |
| Bend angle | ± 0.5° | After springback compensation |
| Ovality (round tube, no mandrel) | ≤ 5% of OD | Per ASTM A500 / EN 10210 |
| Ovality (round tube, with mandrel) | ≤ 2% of OD | Mandrel bending service available |
| Wall thinning (outer arc) | ≤ 15% | Typical; varies with D/t ratio |
| Straight tangent length | ± ¼" | Minimum tangent required for tooling |
Minimum bend radius is approximately 3× OD for round tube without mandrel; 2× OD with mandrel.
Plate Rolling
Flat plate rolled into cylinders, cones, or curved sections. Tolerances depend on plate thickness, width, and material grade.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Cylinder diameter | ± ¼" on diameter | Measured at mid-height |
| Out-of-round | ≤ ½" difference max/min diameter | For cylinders ≤ 48" dia. |
| Seam gap (before welding) | ≤ 1/16" | Tack-welded seam; weld prep extra |
| Cone half-angle | ± 0.5° | |
| Flat spot at pinch point | ≤ 2× plate thickness | Inherent to 3-roll process; can be minimized |
| Length / height | ± 1/8" |
Channel Rolling
C-channels and MC-channels bent the easy way (flanges out) or hard way (flanges in). Hard-way bending produces more flange distortion.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Radius tolerance | ± ¼" | Centerline of web |
| Flange distortion (easy way) | ± 3/16" per foot | Flanges may spread slightly |
| Flange distortion (hard way) | ± 5/16" per foot | Flanges compress inward; more pronounced |
| Twist | 1° per 10 ft | |
| End squareness | ± 1/8" |
Induction Bending
Pipe and structural sections bent using a localized induction heating coil. Produces tight radii with minimal distortion. Tolerances per ASME B16.49 and project specifications.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Bend angle | ± 0.5° | After cooling and springback |
| Bend radius | ± 1% of specified radius | Centerline radius |
| Ovality (pipe) | ≤ 3% of OD | Per ASME B16.49 §6.4 |
| Wall thinning | ≤ 12.5% of nominal wall | Per ASME B31.3 |
| Out-of-plane | ± 1/8" per foot of tangent | |
| Tangent length | ± ¼" | Each end |
CNC Plasma Cutting
Flat plate cut to profile from DXF, DWG, or PDF files. Tolerances depend on plate thickness and material. Fine-cut consumables used for tighter tolerances.
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| Profile accuracy (≤ ½" plate) | ± 1/16" | Fine-cut consumables |
| Profile accuracy (> ½" plate) | ± 3/32" | Standard consumables |
| Kerf width (typical) | 3/32" – 3/16" | Varies with thickness and amperage |
| Squareness of cut edge | ≤ 3° bevel | Per AWS C4.1 Class 1 |
| Hole diameter (≥ 1× thickness) | ± 1/16" | Holes smaller than thickness not recommended |
| Edge roughness (Ra) | ≤ 500 µin (12.5 µm) | Smooth finish; secondary grinding available |
Files accepted: DXF, DWG, PDF. Provide 1:1 scale. Nest optimization included at no charge.
Pipe & Bar Threading
NPT, NPS, and UNC/UNF threads cut on pipe, bar, and rod. Tolerances per ASME B1.20.1 (pipe threads) and ASME B1.1 (unified threads).
| Parameter | Standard Tolerance | Notes |
|---|---|---|
| NPT thread class | Class 1 (standard) | Per ASME B1.20.1 |
| Thread engagement length | ± 1 thread pitch | |
| UNC/UNF thread class | 2A external / 2B internal | Per ASME B1.1 |
| Concentricity | ≤ 0.005" TIR | Thread axis to bar axis |
| Thread runout | ≤ 2 threads | Incomplete threads at start/end |
Tolerances listed are standard shop practice and general industry guidelines. Project-specific tolerances in contract documents, AISC AESS categories, or applicable codes (ASME, AWS, ASTM) take precedence. Contact us before finalizing specifications if your project has unusual requirements.
Many of our standard tolerances can be tightened for architecturally exposed steel, precision assemblies, or code-critical applications. Send us your drawings and we'll confirm feasibility and pricing.