Tolerance Stack-Up Calculator
Add each dimension in the chain with its nominal value and bilateral tolerance. Worst-case sums all tolerances directly; RSS (root-sum-square) statistically combines them, valid when contributors are independent and normally distributed.
| Dimension / Feature | Nominal (mm) | +Tol (mm) | -Tol (mm) | Direction |
|---|
Direction ±1 lets you subtract a dimension from the chain (e.g. an internal feature measured from the opposite datum). Worst-case = Σ|tolerances|; RSS assumes a ~99.73% (±3σ) confidence band when contributors are independent.
ISO Tolerance Grade (IT) Value
Computed from the ISO 286-1 standard tolerance unit formula: i (μm) = 0.45·D^(1/3) + 0.001·D, where D is the geometric mean of the size range.
Hole-Basis Fit Calculator (H-hole)
Standard hole-basis system: hole = H (EI = 0). Choose a shaft letter to get clearance / interference limits. Fundamental deviations below are engineering-reference approximations — cross-check against IS 919 / ISO 286-2 tables before releasing to production or inspection.
Common Preferred Fits Reference
| Fit | Type | Typical Application |
|---|---|---|
| H11/c11 | Loose running | Wide commercial tolerances, easy assembly, dusty/rough conditions |
| H9/d9 | Free running | High-speed shafts, multiple bearings, large temp. variation |
| H8/f7 | Close running | Machine tool spindles in bushings, accurate location + free running |
| H7/g6 | Sliding | Precision sliding parts, not intended to run freely, spigots |
| H7/h6 | Locational clearance | Accurate location, free assembly/disassembly, no perceptible play |
| H7/k6 | Locational transition | Precise location, slight interference possible, keyed shafts |
| H7/n6 | Locational transition | More precise location than k6, greater interference tendency |
| H7/p6 | Locational interference | Parts requiring rigidity/alignment, pressed assembly, gears on shafts |
| H7/s6 | Medium drive | Permanent/semi-permanent assemblies, shrink fit on light sections |
| H7/u6 | Force / shrink fit | Heavy interference, coupling hubs, press-fit bushes |
Theoretical Surface Finish (Turning)
Theoretical peak-to-valley model for a round-nosed single-point tool: Ra (μm) ≈ f² / (32 × r) × 1000, where f = feed (mm/rev), r = tool nose radius (mm). Actual finish is typically higher due to BUE, vibration, tool wear and material behaviour.
Ra / Rz / N-Grade Reference
| N Grade | Ra (μm) | Ra (μin) | Typical Process |
|---|
Hardness Scale Converter
Approximate conversion per ASTM E140 correlation (steel only). Enter a value in any one scale — the others populate by interpolation against the reference table below.
Approximate correlation only — not valid for austenitic stainless, non-ferrous, or thin/case-hardened sections. Use direct hardness testing per the applicable scale for certification purposes.
Reference Table (Steel)
| HRC | HB | HV | Approx. Tensile (MPa) |
|---|
Bolt / Stud Torque & Preload Calculator
T = K × F × D (short-form torque-tension relationship). K = nut factor (friction condition), F = target preload (N), D = nominal bolt diameter (m).
B7 (ASTM A193) values shown are for stud diameters ≤ 2.5 in (yield reduces above that). This is a general engineering estimate — for API 6A / ASME flange assemblies use the bolt-up procedure and torque sequence specified in the job's approved ITP.
Press-Fit / Shrink-Fit Interference Calculator
Lamé thick-cylinder equations for a solid or hollow shaft pressed into a hub, both same material by default.
Contact pressure p = δ / [ D·( (1/E_o)·((Do²+D²)/(Do²−D²)+ν) + (1/E_i)·((D²+Di²)/(D²−Di²)−ν) ) ]. Shrink-fit ΔT = δ/(α·D) + margin. Assembly (push) force F = π·D·L·p·μ.
Machining Allowance Reference — Casting
Typical stock allowance per side (mm) before final machining, by casting process and governing dimension.
| Governing Size (mm) | Sand Casting | Shell Mould | Investment Casting | Die Casting |
|---|---|---|---|---|
| Up to 100 | 2.5 - 4 | 1.5 - 2.5 | 0.3 - 0.8 | 0.2 - 0.5 |
| 100 - 250 | 3.5 - 5 | 2 - 3 | 0.5 - 1 | 0.3 - 0.6 |
| 250 - 500 | 5 - 7 | 2.5 - 4 | 0.8 - 1.5 | 0.4 - 0.8 |
| 500 - 1000 | 6 - 9 | — | 1 - 2 | — |
| Above 1000 | 8 - 12+ | — | — | — |
Machining Allowance Reference — Forging
| Governing Size (mm) | Open-Die Forging | Closed-Die Forging |
|---|---|---|
| Up to 100 | 3 - 5 | 1.5 - 2.5 |
| 100 - 250 | 4 - 6 | 2 - 3 |
| 250 - 500 | 6 - 9 | 2.5 - 4 |
| 500 - 1000 | 8 - 14 | 3.5 - 5 |
| Above 1000 | 12 - 20+ | — |
Open-die (hand/cogged) forgings for oilfield hubs, hangers and flanges typically need generous allowance on the OD/faces to clean up ultrasonic-indicated surface and decarb layer — confirm with the forge shop's UT/surface prep requirement before finalizing rough machining size.
Grinding / Finishing Stock (After Rough/Semi-Finish Turning)
| Diameter Range (mm) | Grinding Stock per Side (mm) |
|---|---|
| Up to 50 | 0.15 - 0.25 |
| 50 - 120 | 0.20 - 0.35 |
| 120 - 250 | 0.30 - 0.45 |
| 250 - 500 | 0.40 - 0.60 |
| Above 500 | 0.50 - 0.80 |
Cross-Section Property Calculator
Area, moment of inertia, section modulus and radius of gyration for common shapes — feeds directly into the Shaft/Beam Stress tab.
Combined Bending + Torsion Stress (Shaft)
σ = 32M/(πD³) τ = 16T/(πD³) σ_vm = √(σ² + 3τ²). Compares equivalent (von Mises) stress against material yield with a chosen factor of safety.
Beam / Shaft Deflection
Uses a single applied load/UDL case per standard beam formulas. Enter I from the Section Properties tab, or calculate it there and copy the value across.
Critical Speed Estimate (Rayleigh Approximation)
Nc (RPM) ≈ 946 / √(δ_static in mm). Simplified single-mass approximation from static deflection — useful as an early screening check, not a substitute for a full rotordynamic analysis on critical rotating equipment.
Weld Joint Strength Calculator
AWS-style allowable stress design. Fillet weld allowable shear ≈ 0.3 × F_EXX (electrode classification minimum tensile strength). Full-penetration groove welds are typically rated at the base metal's allowable stress.
Reference calculation only — final weld sizing, joint design, and NDE extent must follow the applicable code (AWS D1.1, ASME IX, API 1104 etc.) and the approved WPS/ITP for the job.
Process Capability (Cp / Cpk) Calculator
Paste measurement data (comma, space, or newline separated) or enter mean & standard deviation directly.
Cpk Rating Guide
| Cpk Value | Rating | Interpretation |
|---|---|---|
| < 1.00 | Inadequate | Process not capable — expect out-of-spec parts; investigate variation source before release |
| 1.00 - 1.33 | Marginal | Capable but low margin — tighten control, monitor closely, common minimum for non-critical features |
| 1.33 - 1.67 | Good | Common requirement for critical/functional dimensions |
| > 1.67 | Excellent | High confidence — often expected for safety-critical or customer-mandated features |
Cpk assumes the data is from a stable, in-control process and approximately normally distributed. A high Cpk on an out-of-control process (special-cause variation present) is not meaningful — check a control chart first.
NDE Method Selection Guide
| Method | Detects | Surface Requirement | Typical Use |
|---|---|---|---|
| Visual (VT) | Surface finish, dimensional, obvious surface defects | Clean, adequate lighting/access | First-line check on every component |
| Liquid Penetrant (PT) | Surface-breaking cracks, porosity, laps | Non-porous surface, clean & dry | Non-ferromagnetic materials, welds, machined surfaces |
| Magnetic Particle (MT) | Surface & near-surface cracks, laps, seams | Ferromagnetic material only | Steel forgings, castings, welds |
| Ultrasonic (UT) | Internal/subsurface flaws, laminations, wall thickness | Reasonably smooth coupling surface | Thick sections, forgings, in-service wall thickness |
| Radiographic (RT) | Internal porosity, inclusions, lack of fusion/penetration | Two-side access for film/detector placement | Weld volumetric inspection, castings |
| Eddy Current (ET) | Surface cracks, conductivity/coating thickness | Conductive material | Tubing, heat exchanger tubes, fast surface scanning |
Discontinuity Types & General Severity Concepts
| Discontinuity | Typical Cause | General Severity Consideration |
|---|---|---|
| Porosity | Trapped gas during solidification/welding | Usually judged on size, density (count per area) and clustering, not single-point size alone |
| Lack of fusion / penetration | Insufficient heat input, poor joint prep, technique | Generally treated as more severe than porosity — planar, stress-risers |
| Cracks | Hydrogen embrittlement, restraint/shrinkage stress, fatigue | Normally rejectable regardless of size in most codes — root cause investigation required |
| Slag inclusion | Trapped flux/slag not removed between weld passes | Judged on length and linear alignment along the weld axis |
| Undercut | Excess travel speed, incorrect angle/amperage | Judged on depth relative to base metal thickness |
This tab is an orientation reference only. Do not use it for accept/reject decisions. Acceptance criteria (indication length, count, spacing, depth limits) vary by code, edition, product form and component class — always apply the exact criteria in the governing code (ASME V/VIII, API 1104, API 6A/6D, ISO, or the job's approved ITP) as it applies to the specific job.
Job Calculation Sheet
Pick results from any calculator tab using "+ Add to Job Sheet", then print or attach this summary to the job's engineering file / ITP.
| Calculation | Result Summary | Added |
|---|