# TechRef — ISO-Toleranzen, mm & Zoll > ISO-Toleranzen, mm & Zoll (iPhone/iPad app by MASARU KATO.) - Source: https://appshunter.io/ios/app/techref/id6775818457 (this page in markdown: same URL + `.md`) - Developer: [MASARU KATO](https://appshunter.io/developer/1883480774) - Category: Utilities, Productivity - Price: Free with in-app purchases - Age rating: 4+ - Requires: iOS 17.6 · 4 MB - Languages: American English, French (France), German (Germany), Italian, Japanese, Korean, European Portuguese, Chinese (Simplified, China), European Spanish, Chinese (Traditional, Taiwan) - Released: 2026-09-16 - Data updated: 2026-10-11 ## What is TechRef? The drawing says 50.000 +0.200 / -0.000. The machine needs 50.100. TechRef does that math, converts it into every unit, and records what you measure. Built for the everyday questions on the shop floor. WHY THE CENTER VALUE MATTERS The center of an asymmetric tolerance is not the nominal size. TechRef calculates the true center and the full band, so you get it right in one setup. Input: 50.000 +0.200 / -0.000 Center: 50.100 Range: 50.000 – 50.200 mm 50.1000 (50.0000 – 50.2000) in 1.9724 ( 1.9686 – 1.9763) TOLERANCES FROM THE STANDARD (TechRef Pro) Pick an ISO 2768 class (f, m, c, v) or an ISO 286 fit (hole H7, shafts g6 to p6), and TechRef looks up the deviations for your size. Pick a shaft to see how it fits an H7 hole: clearance, transition or interference. Use ISO, JIS, EN, DIN or BS names; only standards officially identical to ISO are listed. TABLES AND CALCULATORS • Tolerance tables (TechRef Pro): ISO 2768 and ISO 286 (H7, g6 to p6, fits with H7), up to 500 mm • Tap drill charts (TechRef Pro): Metric, Unified and Whitworth, with minor diameter limits. Sizes that could not be verified are left out • Drill size charts: number, letter and fractional drills in inches and mm • Cutting speed and feed: spindle speed, cutting speed and feed rate, in mm and m/min or inch and SFM. Formulas only RECORD WHAT YOU MEASURE Add measured values to any point in a sheet. Each entry updates the count, mean, max, min, range, standard deviation, deviation from target, out-of-tolerance count, Cp and Cpk. Drawing: 25.000 ±0.100 Measured: 25.02 / 25.05 / 24.98 / 25.12 / 25.03 Mean: 25.040 (+0.040 from target) Out of tolerance: 1 / 5 The target is the tolerance center, so you see which way to adjust. Drawing in mm, measuring in inches? Record in your own unit. Free, and not counted toward the save limit. INSPECTION SHEETS AND CSV Create a sheet per part with points, each with its own dimension and tolerance. Export CSV per point or per measured value. 13 CATEGORIES, 100+ UNITS Length, pressure, torque, force, temperature and more. Show only the units you use, from mm and inch to bar, psi, kgf/cm², N·m and lbf·ft. Factors come from exact definitions, never rounded approximations. SAFE-SIDE ROUNDING Bands are rounded inward, so a part inside the band on screen is inside it for real. 10 LANGUAGES English, Japanese, German, French, Italian, Spanish, Portuguese, Korean, Simplified Chinese and Traditional Chinese. Follows your device, or choose in Settings. FREE, AND TechRef Pro Conversions, manual tolerances, drill charts, the cutting calculator, Sheets, measured values and CSV export are free. Saving dimensions has a limited number of free saves, then once per hour. TechRef Pro, a one-time purchase, removes the limit and unlocks tap drill charts, tolerance tables and tolerances from the standard. No subscription. EVERYTHING STAYS ON YOUR DEVICE No server, fully offline. No ads, no tracking, no analytics, no account. ALSO History with search, labels and memos · 1 to 6 decimal places · How to Use · Dynamic Type · Light and dark · iPhone and iPad ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | TechRef Pro | $6.99 | one-time | ## Version history (last 5 releases) ### 2.0.0 — 2026-10-11 10 LANGUAGES TechRef now speaks English, Japanese, German, French, Italian, Spanish, Portuguese, Korean, Simplified Chinese and Traditional Chinese. It follows your device language, or choose one in Settings > Language. CSV files stay in English. Cp AND Cpk Measured values now show the process capability indices Cp and Cpk, and they are added to the CSV export. FITS WITH H7 (TechRef Pro) Pick a shaft (g6 to p6) in the tolerance input to see how it fits an H7 hole: clearance, transition or interference, with the maximum and minimum clearance in µm. A new table lists every combination up to 500 mm. TORQUE A new Torque category: N·m, kN·m, N·cm, kgf·m, kgf·cm, lbf·ft, lbf·in and ozf·in. CUTTING SPEED AND FEED A new calculator in Reference: spindle speed, cutting speed and feed rate, in mm and m/min or inch and SFM. ### 1.4.0 — 2026-10-09 MEASURED VALUES Record as many measured values as you like for each point in a sheet. Every entry updates the count, mean, max, min, range, standard deviation, deviation from target (the tolerance center) and the number of values out of tolerance. Out-of-tolerance values are shown in red. • Tap a value to change or delete it, Edit to reorder, Undo to take back the last change • Record in a different unit from the drawing (drawing in mm, measuring in inches). Target and limits are converted to that unit • Black: as entered. Blue: converted. Red: out of tolerance • Measured values are free and don't count toward the save limit MEASURED VALUES AS CSV Export one row per value to the clipboard or the Files app, with target, limits, deviation, pass/fail and date. Ready to sort or chart in Excel. After exporting, clear the measured values of one part or all sheets at once. Dimensions and tolerances stay. EN, DIN AND BS STANDARD NAMES Alongside ISO and JIS, you can now choose EN, DIN or BS names. Each is officially published by its standards body as technically identical to ISO. General tolerance classes show your standard's name with the ISO form, such as DIN ISO 2768-1 m (ISO 2768-m). HOW TO USE A new How to Use page in Settings explains each feature in brief. The first time you reach a feature, a short tip appears once. ### 1.3.0 — 2026-09-27 Added standard-based tolerance lookup. Pick an ISO 2768 (general tolerance) or ISO 286 (fit) class, and TechRef shows the upper/lower deviation for the size you entered. The same tables also show under JIS B 0405 / JIS B 0401 names (TechRef Pro). Added general tolerance and fit reference tables (TechRef Pro). Other changes: - Search added to the table list - Choose which classes and ranges appear, in Settings - Added "Reset to Defaults" - Added a "Standards and Data" screen showing sources - Added first-run Quick Setup - Terms are shown again after every update - History is now searchable by standard name - Tables keep their first column and header row in place while scrolling ### 1.2.0 — 2026-09-24 NEW: TAP DRILL TABLES (TechRef Pro) • Tap drill sizes for Metric (coarse M1–M48, fine M8×1–M48×3), Unified (UNC, UNF, UNEF, #0 to 2") and Whitworth (BSW, 1/16" to 2"). • Every size lists the minimum and maximum minor diameter of the internal thread, so you can tell on the spot whether your drill will do. • Every tap drill size has been checked against a Japanese tap manufacturer's JIS-based chart to confirm it falls within the allowed range. Sizes that could not be verified are not included. IN-APP PURCHASE RENAMED • "Unlimited Saves" is now "TechRef Pro". Along with unlimited saving, it unlocks the tap drill tables. • If you have already purchased, the tap drill tables are included at no extra cost. NEW JAPANESE UNITS • Volume: sho (升), to (斗), hyo (俵) and koku (石). • Weight: the rice-trade units go, sho, to, hyo and koku (1 hyo = 60 kg). • Turn them on in Settings > Units to Show. MORE ACCURATE CONVERSIONS • Factors for oz, ton (UK), shaku, sun, bu, ken, tsubo, lbf, psi, horsepower, BTU, mmHg, torr, knots and more are now calculated from their exact definitions instead of truncated approximations. • The go (合) now follows its legal definition (1 sho = 2401/1331 L). The last digits of some results may change. READABILITY • Numbers no longer wrap mid-value, and screens keep their layout at larger text sizes. • Unit names in the results list now stay on one line. OTHER • On first launch, you are now asked to agree to the Privacy Policy and Disclaimer. Next, I plan to add a feature for saving frequently used tolerances. If there are other features you would like, I am happy to discuss them, within the limits of my understanding and technical skills. ### 1.1.0 — 2026-09-22 • Fractional drill sizes: the Drill Sizes table now covers number (#80–#1), letter (A–Z) and fractional (1/64"–1") drills, each with inch and mm equivalents. • Drill Sizes (By Size): a new table that merges all three systems into one list sorted by diameter, so you can find the closest drill whichever system it comes from. • Over 90 units, your choice: every unit is now available — bar, atm, mmHg, torr, kgf/cm², knots, Mach, BTU, metric horsepower, microns and more. Choose which ones appear in Settings > Units to Show. Traditional Japanese units can be switched on too. ## More apps by MASARU KATO - [MAKE10 - Kids Game Collection](https://appshunter.io/ios/app/make10-kids-game-collection/id6760253962) - [PriceWise / 単価比べ](https://appshunter.io/ios/app/pricewise/id6764689863) - [OMOHIDE DECK](https://appshunter.io/ios/app/omohide-deck/id6810569599) All apps by MASARU KATO: https://appshunter.io/developer/1883480774 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-11.*