Four value classifications
- Normative standard value: reproduced only when access and permission allow, with edition and scope.
- Manufacturer recommendation: attributed to the named maker and treated as application guidance.
- Calculated reference: generated from a displayed formula and explicit inputs.
- Workshop guidance: a practical assumption that is not presented as a formal tolerance.
Exact conversion and rounding
Decimal input becomes an integer ratio. One inch equals exactly 25.4 millimeters. The engine performs rational arithmetic and rounds half away from zero only when formatting a requested number of decimal places.
Tap drill methodology
Supported cut-tap results are reviewed manufacturer lookups. Nominal diameter minus one pitch appears only as an approximate cross-check for supported straight 60-degree thread contexts. Forming-tap results appear only when a source-specific pre-hole range exists.
Pipe-thread recommendations retain their documented process context. When current sources disagree—as they do for 1/8-27 NPT—the calculator displays the alternatives and does not manufacture a consensus value.
Clearance-hole methodology
The calculator defaults to documented manufacturer recommendations for the available metric and Unified sizes. A separate planning mode adds explicit diametric allowances: 0.2, 0.5 or 1.0 mm; or 0.008, 0.016 or 0.032 inch. Planning outputs remain clearly identified as calculated guidance and do not reproduce ASME or ISO clearance tables.
Data admission rules
Technical records require a date, source link, methodology, limitations and schema validation. Unsupported combinations remain unavailable until appropriate evidence is added.