Frequently Asked Questions

A tolerance report (or tolerance stack-up report) is a document that shows how individual part tolerances combine to affect a critical assembly dimension. It includes: the dimension chain, nominal and tolerance values, calculation method (WC or RSS), results, sensitivity analysis, and assumptions. Engineers use tolerance reports in design reviews to prove an assembly will work before building prototypes. A good report answers: "Will this fit?" and "Which tolerances matter most?"

A complete tolerance stack-up report includes: • Assembly description and sketch reference • Target specification (min/max acceptable values) • Dimension chain table with nominals, tolerances, and directions • Worst-Case (WC) calculation and result • RSS (statistical) calculation and result • Sensitivity analysis showing contribution percentages • Assumptions (thermal conditions, material, process capability) • Recommendation or design decision TolReport generates all of this automatically in a professional PDF format.

Use Worst-Case when: safety is critical (aircraft, medical), production volume is low, or 100% interchangeability is required. WC assumes all dimensions hit their worst limits simultaneously—conservative but guarantees no assembly failures. Use RSS when: production volume is high (1000+ units), processes are in statistical control (Cpk ≥ 1.33), and some fallout is acceptable. RSS uses statistical averaging and typically yields 30–50% tighter stack-ups than WC. Most engineers run both analyses and present them side-by-side in design reviews.

Sensitivity shows which dimensions contribute most to your total variation. It's calculated as (tolerance²) / (sum of all tolerances²) × 100%. A dimension with 40% sensitivity contributes 40% of your RSS variation. Focus tolerance reduction efforts on high-sensitivity dimensions—tightening a 5% contributor won't meaningfully improve your stack-up.

The WC and RSS formulas are standard mechanical engineering math—the same formulas you'd use in Excel or by hand. TolReport just automates them. However: garbage in, garbage out. The accuracy depends on your inputs: nominal dimensions, tolerances, and whether your sign conventions are correct. Always verify a few manual calculations when learning the tool.

Free includes: up to 3 saved projects, up to 5 dimensions per stack, full WC & RSS analysis, sensitivity charts, and all engineering templates (clevis, shaft-bore, lid-box, etc.). Free is enough to learn the workflow and run quick calculations. You can use it indefinitely.

Pro ($19/month or $149/year) adds: unlimited projects, unlimited dimensions per stack, and review-ready PDF export. The PDF export is the main reason engineers upgrade—it produces professional reports you can put directly in a design review or customer deliverable.

The free tier gives you full access to the calculation engine and templates. The only locked feature is PDF export and the project/dimension limits. If you need to evaluate PDF quality before subscribing, email support@tolreport.com and we can provide a sample report.

The PDF includes: project name, revision, date, assembly target (min/max), all dimensions with nominals and tolerances, WC and RSS results, pass/fail status, sensitivity breakdown, assumptions checklist, and notes. It's formatted for direct inclusion in design review packages—no reformatting needed.

Not currently. The template is designed for general mechanical engineering use. If you have specific formatting requirements (company logo, custom fields), email us—we're considering customization for future versions.

It depends on whether you're signed in: Anonymous (not signed in): All project data stays in your browser (localStorage). Nothing is sent to our servers. Your stack-ups never leave your machine. Signed in: Your projects are stored on our servers (Cloudflare) tied to your account email. This enables cross-device sync—your stack-ups are available on any browser where you sign in.

Anonymous users: No. We cannot see your projects, dimensions, or any data you enter. The app runs entirely in your browser. Signed-in users: Yes, we store your project data on our servers to enable cross-device sync. We do not share, sell, or analyze your engineering data. See our Privacy Policy for details.

Anonymous users: Your projects will be lost. localStorage is browser-specific and clears with browser data. Always export important stack-ups to PDF before clearing browser data. Signed-in users: Your projects are safe on our servers. Sign in again on any device to restore them.

TolReport handles 1D (linear) tolerance stack-ups only. This covers most mechanical engineering use cases: shaft-bore fits, gap analyses, clearance checks, assembly stack-ups. For 3D tolerance analysis with GD&T simulation, you need dedicated software like CETOL, 3DCS, or Sigmetrix. Those tools cost $10,000+/year and require CAD integration.

Yes, with conversion. GD&T callouts (position, profile, flatness) can be converted to equivalent bilateral tolerances for 1D stack-ups. Example: A position tolerance of Ø0.5 at MMC becomes ±0.25 for stack-up purposes. See our guide on GD&T in Tolerance Stack-Ups for detailed conversion formulas.

Mechanical engineers doing tolerance analysis for design reviews, customer deliverables, or internal documentation. Common industries: aerospace, automotive, medical devices, consumer products, industrial equipment. If you're building Excel stack-ups today and want something more reliable and professional, TolReport is for you.

TolReport is a calculation aid, not a certified engineering tool. You are responsible for verifying results and ensuring they meet your application requirements. For safety-critical designs (aircraft, medical, automotive safety), always have calculations reviewed by a qualified engineer and follow your organization's verification procedures.

Email support@tolreport.com immediately with details. We take calculation accuracy seriously and will investigate and fix any confirmed issues. The core math is covered by unit tests, but edge cases can slip through. User reports help us improve.