Fits and tolerance calculators for mechanical design. Four tools on one page: tolerance stack-ups, ISO 286 limits and fits, MMC bonus tolerance, and process capability. Every result comes with a plain-language verdict, and a learn mode explains the terms for anyone still getting comfortable with GD&T.
Live demo: https://aswad-adel.github.io/scribe/
| # | Tool | Question it answers | Output |
|---|---|---|---|
| 01 | Tolerance Stack-Up | Will my assembly fit together? | Worst-case and RSS gap limits, contribution chart |
| 02 | ISO 286 Limits & Fits | How tight is this hole-and-shaft pair? | Clearance or interference in µm, tolerance zones drawn to scale |
| 03 | MMC Bonus Tolerance | How much extra tolerance did a part earn? | Total position tolerance and virtual condition |
| 04 | Process & Material Limits | Can my process hold this tolerance? | Achievable ± for 11 processes at your size |
Stack-ups: worst case is the arithmetic sum of the chain tolerances. RSS is the root sum of squares, treating each ±tol as three standard deviations of an independent, centered process.
Fits: IT grades come from the ISO 286 tolerance factor i = 0.45·D^(1/3) + 0.001·D with the standard grade multipliers. Fundamental deviations are tabulated per ISO 286-2 for nominal sizes over 3 and up to 120 mm, hole basis, across the nine preferred fits from H11/c11 to H7/s6.
MMC: bonus tolerance accrues one for one as a feature of size departs from maximum material condition, and the virtual condition boundary stays fixed, per ASME Y14.5.
Process capability: machining rows map each process to the IT grade it holds in routine production. Printing and molding rows use published service tolerances in the form "±X mm or ±Y% of dimension, whichever is greater."
| Case | SCRIBE output | Reference |
|---|---|---|
| Ø25 H7/g6 | +7 / +41 µm clearance | ISO 286-2 tables |
| Ø25 H7/p6 | 1 to 35 µm interference | ISO 286-2 tables |
| IT7 at 30 to 50 mm | 25 µm | Standard tolerance formula |
This is an educational tool. Check released drawings against the standards themselves or Machinery's Handbook.
I wrote SCRIBE around my design engineering internship at Saudi Mais for Medical Products in Riyadh, where I reviewed injection mold drawings before release. The company ran no formal quality system, so tolerance calls came down to the engineer checking the print. The four tools are the checks that job demanded: turning fit callouts into limits, stacking tolerances across a cap and spout assembly, and deciding whether a process could hold 0.02 mm on parts that touch needles before that number went on a drawing. The idea is older than the internship. I started guessing at clearances in F1 in Schools, and this is the calculator I wished I had then.
npm install
npm run dev
Build for production with npm run build. Deploy to GitHub Pages with npm run deploy after setting the Pages source to the gh-pages branch.
React 18 and Vite. No UI libraries. All styling is inline against a single token set, so the whole app is one component file: src/App.jsx.
Adel Aswad, Mechanical Engineering, University of Florida. LinkedIn: https://www.linkedin.com/in/adel-aswad
MIT license.