Provenance

How This Data Is Built, Sourced and Checked

https://shopmath.org/data · data verified August 1, 2026

2,250 verified values across 8 datasets, each computed from a published standard’s own formulas or compiled from independent sources that agree cell-for-cell, then checked against published tables before it shipped. Nothing here is transcribed from a chart of unknown origin.

Datasets: 8
Values: 2,250
Verified: August 1, 2026

Every Dataset on This Site

Datasets, sizes, derivation method and governing standard
Dataset	Values	Method	Standard
Standard drill index — number, letter, fractional, metric	397	computed+compiled	ANSI/ASME B94.11M; BS 328
ISO 286 IT grades, fundamental deviations and fits	1,162	compiled	ISO 286-1:2010, ISO 286-2:2010
Sheet-metal gauge thicknesses — steel, galvanized, aluminium, US Standard	136	computed	15 U.S.C. 206; Manufacturers' Standard Gauge; Brown & Sharpe / AWG
GD&T geometric characteristics and modifiers	22	compiled	ASME Y14.5 (cited, not reproduced); ISO 1101
SAE AS568 o-ring sizes and gland design	349	computed+compiled	SAE AS568; MIL-G-5514G (public domain, inactive for new design)
ISO metric screw threads — M1.6 to M64, coarse and fine	68	computed+compiled	ISO 68-1, ISO 261, ISO 262, ISO 965-1, ISO 898-1
NPT and NPTF taper pipe threads	34	computed+compiled	ASME B1.20.1, ASME B1.20.3; public-domain primary FED-STD-H28/7A (1984)
Unified inch screw threads — UNC, UNF, UNEF	82	computed	ASME B1.1 (reference values based on the ASME B1.1 system; not a compliance claim)

“Computed” means the values are derived from the standard's own formulas and then checked against a published table. “Compiled” means independent public sources were compared cell-for-cell and had to agree. Where a formula exists but does not reproduce the published table closely enough to trust, it is used only as a validation harness — never as the shipped value.

Sources, Validation and What Is Deliberately Excluded

Each dataset below names its source, what it was checked against, and the scope it does not cover. The exclusions are the important part: a reference that quietly guesses at the edges is worse than one that stops.

Standard drill index — number, letter, fractional, metriccomputed+compiled

bd_warehouse drill_sizes.csv (Apache-2.0) + Wikipedia Drill bit sizes (CC BY-SA 4.0); fractional and metric computed from ANSI B94.11M / BS 328 increment patterns

Verified against drills: 31 checks passed across 1 harness(es)

Part computed from the standard's formulas, part compiled from agreeing public sources.

ISO 286 IT grades, fundamental deviations and fitscompiled

saucecode/ISO286 (LGPL-2.1) + parkergreene/isofits (MIT), cross-checked cell-for-cell

Verified against fits-iso286: 2067 checks passed across 3 harness(es)

Compiled from independent public sources that agree cell-for-cell.

Sheet-metal gauge thicknesses — steel, galvanized, aluminium, US Standardcomputed

15 U.S.C. 206 statutory weights (public domain); MSG, galvanized and Brown & Sharpe formulas

Verified against gauges: 137 checks passed across 1 harness(es)

Computed from the standard's formulas, then checked against published tables.

GD&T geometric characteristics and modifierscompiled

Unicode Character Database (Unicode License v3); characteristic list cross-checked against NASA MSFC GD&T Basics (public domain); descriptions written from scratch

Verified against gdt: 98 checks passed across 1 harness(es)

Compiled from independent public sources that agree cell-for-cell.

SAE AS568 o-ring sizes and gland designcomputed+compiled

bd_warehouse o-ring_parameters.csv (Apache-2.0) + KasperCalc oring-sizes.js (MIT), agreeing on all 349 sizes; OD computed; gland depth computed from squeeze %

Verified against o-rings: 21 checks passed across 3 harness(es)

Part computed from the standard's formulas, part compiled from agreeing public sources.

ISO metric screw threads — M1.6 to M64, coarse and finecomputed+compiled

ISO 68-1 basic profile computed; ISO 261/262 diameter-pitch pairs and 6H class limits compiled

Verified against threads-metric: 215 checks passed across 3 harness(es)

Part computed from the standard's formulas, part compiled from agreeing public sources.

NPT and NPTF taper pipe threadscomputed+compiled

ASME B1.20.1 taper formulas computed; pipe OD, tpi, L1 and L4 compiled

Verified against threads-pipe: 98 checks passed across 1 harness(es)

Part computed from the standard's formulas, part compiled from agreeing public sources.

Unified inch screw threads — UNC, UNF, UNEFcomputed

NBS Handbook H28 (1969) Part I §§6-7 formula system (public domain, 17 U.S.C. 105)

Verified against threads-unified: 1064 checks passed across 3 harness(es)

Computed from the standard's formulas, then checked against published tables.

Assumptions

Standard drill index — number, letter, fractional, metric — Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.
ISO 286 IT grades, fundamental deviations and fits — COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula.
Sheet-metal gauge thicknesses — steel, galvanized, aluminium, US Standard — EXCLUDED: stainless steel (genuinely ambiguous convention, only one source in hand), zinc, copper, brass, steel tube wall.
GD&T geometric characteristics and modifiers — EXCLUDED: all ASME Y14.5 definitional text, worked examples and figures. Every description on this site is original prose.
SAE AS568 o-ring sizes and gland design — A fabricated-dataset negative control is asserted against on every run. EXCLUDED: groove width, corner radius, diametral clearance, back-up ring widths, surface finish, all dynamic glands, the 900-series, and ISO 3601 metric sizes.
ISO metric screw threads — M1.6 to M64, coarse and fine — EXCLUDED: ISO 965-1 tolerance-grade formulas (not located — data-sourcing.md open item 2), 6g external limits (single-sourced), form tap drills, M68-M100 (verified demand cliff at M64).
NPT and NPTF taper pipe threads — L1 is tabulated, not derivable (data-sourcing.md §3.3). EXCLUDED: NPTF crest/root truncation limits (single-sourced), NPSM/NPSC/NPSF straight pipe threads, BSPT/BSPP.
Unified inch screw threads — UNC, UNF, UNEF — Le = 1D for UNC/UNF, 9P for UNEF — determined empirically against H28 Table 2.21, resolving data-sourcing.md open item 5. EXCLUDED: form (roll) tap drills, class 1A/1B limits, class 1AR allowances, constant-pitch UN series.

Data last verified

August 1, 2026

How this data is built and checked →

The Rules This Reference Is Built Under

No unverifiable number ships. Where no free, verifiable source exists, the topic is left out rather than filled in from a chart of unknown provenance.
Every value carries its source, method and check. Those three fields are columns in the database, not prose written per page, so they cannot drift from the number they describe.
Assumptions are stated, and changeable. Thread engagement is the obvious one: 75% is a convention, not a fact, so every tap drill table shows 50% to 85% and says what the chosen drill actually produces.
Disagreements are shown, not resolved silently. Where a computed recommendation differs from the traditional published chart, both appear with the reason.
URLs are permanent. A reference you cannot cite next year is not a reference.

Row Counts in the Published Database

The database ships inside the deploy, so the site you are reading and the numbers below are the same artifact.

Row counts per table in the published database
Table	Rows
datasets	8
drills	397
fit_designation_sizes	312
fit_designations	24
fit_sizes	208
fits	16
fundamental_deviations	1,058
gauges	136
gdt_symbols	22
it_grades	104
o_ring_glands	6
o_rings	349
thread_class_limits	365
thread_pipe_dims	34
thread_tap_drills	1,050
threads	184

How to Cite This Reference

Citation

ShopMath. "How This Data Is Built, Sourced and Checked." ShopMath, verified August 1, 2026, https://shopmath.org/data

BibTeX

@misc{shopmath-data,
  title        = {How This Data Is Built, Sourced and Checked},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/data}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/data

Screw thread reference · All reference tables