DatumNest: Tolerance Stack
Worst Case & Monte Carlo
$0.99 · Designed for iPad. Not verified for macOS.
Worst case, RSS, Monte Carlo, Cp/Cpk and tolerance allocation for your own saved stacks. Unlimited stacks, CSV, PDF and backups. One purchase, no subscription.
DatumNest is a tolerance stack-up workbench for product engineers, machinists, quality teams and engineering students. Build a signed one-dimensional dimension chain, then see worst case, RSS, modified RSS, statistical and Monte Carlo results side by side, with Cp, Cpk, predicted yield and ppm against your spec limits.
NEW IN 2.0
- Unlimited saved stacks in millimeters or inches
- Asymmetric tolerances (e.g. 10.000 +0.000/−0.120), editable sensitivity coefficients and fixed (purchased) parts
- Method comparison: worst case, RSS, modified RSS (1.5 × RSS), distribution-aware statistical ±3σ and Monte Carlo
- Cp, Cpk, predicted yield and ppm out of spec
- Seeded, repeatable Monte Carlo with 10,000, 50,000 or 100,000 runs, histogram with spec limits and percentiles
- Tolerance allocation: resize adjustable tolerances to make the worst case fit or reach a Cpk target, saved as a new stack
- Mean centering and a "best part to tighten" ranking
- Side-by-side comparison of two saved stacks
- CSV import and export of dimension chains
- Full backup and restore of every stack (restore never deletes; a safety copy is kept)
- PDF engineering report with histogram, methods and chain
- A written method guide with formulas and a worked example computed live by the app
HOW IT WORKS
Walk the loop around the closing gap and enter each contributor with its nominal, plus and minus tolerance, direction (+ or −), sensitivity and distribution (normal ±3σ, uniform or triangular). DatumNest converts unequal tolerances to their midpoint and half-width, sums them, and shows which contributors own the variation so you know what to tighten first.
PRIVATE AND ONE-TIME
Everything runs on your device. No account, no subscription, no in-app purchases, no ads, no analytics and no network use. Your stacks stay in the app until you export them.
DatumNest is an engineering screening and communication tool. Confirm datum schemes, geometric effects, correlations, distribution assumptions, process capability, units and acceptance criteria with qualified design and quality personnel.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
DatumNest 2.0 is a major upgrade:
- Unlimited saved stacks in mm or inches (a stack you edited in 1.0 carries over as your first saved stack)
- Asymmetric tolerances, editable sensitivities and fixed parts
- Worst case, RSS, modified RSS, statistical and Monte Carlo side by side with Cp, Cpk, yield and ppm
- Tolerance allocation to a worst-case or Cpk target, mean centering and a best-part-to-tighten ranking
- Stack comparison, CSV import/export, full backup and restore, improved PDF report
- New method guide with a live worked example
- Fixed: Monte Carlo chart axis starting at zero, low-contrast text, dark mode colors, negative values that could not be typed
- Removed the generic plate gallery and the separate sandbox panel in favour of tools that use your own stacks
The developer, Robert Corbin, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Robert Corbin
- Size
- 3.2 MB
- Category
- Developer Tools
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Robert Corbin
