amolinari-autotex
19db763899
* feat: expand tapped-hole catalogue with metric fine and Unified sizes * docs: distinguish metric designations from expanded tapped catalogue * feat: add internal pipe catalogue and checked Rc profile data * Connect parallel G and Rp catalogues to cylindrical tapped holes * fix(i18n): register tapped thread catalogue labels * fix(i18n): complete thread labels in required locales
87 lines
5.0 KiB
Markdown
87 lines
5.0 KiB
Markdown
# Tapped-hole catalogue
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The Hole dialog offers ISO metric coarse sizes, 15 additional fine diameter/pitch
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pairs, a finite set of 14 UNC and 14 UNF sizes, and six sizes each for internal
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G/BSPP and Rp parallel pipe threads. This is a verified subset,
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not complete coverage of these standards. Unified sizes range from #4 through
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#12 and 1/4 through 1 inch. Include the family in a designation, for example
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`1/4-20 UNC` or `#10-32 UNF`.
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Internal units are millimetres. Unified screw diameters convert using exactly
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25.4 mm/in; pitch is 25.4 divided by threads per inch. Numbered screw sizes are
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nominal screw diameters, not numbered drill diameters. Pipe fractions are nominal
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labels: G 1/4 has a basic major diameter of 13.157 mm, not 6.35 mm.
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For UNC/UNF, the proposed pilot diameter comes from Guhring's **CUT TAPS,
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approximately 75% theoretical thread** column. Fractional, letter and numbered
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drills are converted to millimetres without rounding away the recommendation.
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These are starting recommendations for cutting taps, not form taps. Material,
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depth, tolerances, drilling accuracy and the tap manufacturer's process guidance
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still determine the appropriate drill; the command's explicit `diameter` can
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override the recommendation.
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Metric holes retain the existing major-minus-pitch estimate, rounded to 0.001 mm.
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This preserves existing command behavior, including M8's 6.75 mm default. It is
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not presented as a tabulated 75% cut-tap recommendation. Existing files retain
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their saved diameter expressions. Custom metric dimensions remain editable, and
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Custom stays selected even when its current dimensions match a catalogue entry.
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Tapped holes create the physical pilot bore and cosmetic thread metadata. The
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separate Thread command and its automatic sizing remain ISO metric only; this
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catalogue does not enable modelled Unified or pipe threads. Rc, external R, NPT,
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thread classes, handedness and sealing behavior are outside this tranche.
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No tapered thread is represented as a cylindrical hole.
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## Parallel G/BSPP and Rp threads
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Both families use a 55-degree profile and a cylindrical pilot bore. Keep G and Rp
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separate: their process-drill recommendations differ. The UI shows the nominal
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pipe designation, actual basic major diameter, pitch/TPI and pilot drill. The
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command accepts canonical labels such as `G 1/4` and `Rp 1/4`, compact forms
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`G1/4` and `Rp1/4`, and `BSPP 1/4` as an alias for G. The separate Thread command
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remains metric-only.
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| Nominal | TPI | Major mm | Pitch diameter mm | Minor mm | G drill mm | Rp drill mm |
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| --- | ---: | ---: | ---: | ---: | ---: | ---: |
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| 1/8 | 28 | 9.728 | 9.147 | 8.566 | 8.75 | 8.5 |
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| 1/4 | 19 | 13.157 | 12.301 | 11.445 | 11.75 | 11.4 |
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| 3/8 | 19 | 16.662 | 15.806 | 14.950 | 15.25 | 14.8 |
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| 1/2 | 14 | 20.955 | 19.793 | 18.631 | 19.0 | 18.5 |
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| 3/4 | 14 | 26.441 | 25.279 | 24.117 | 24.5 | 24.0 |
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| 1 | 11 | 33.249 | 31.770 | 30.291 | 30.75 | 30.2 |
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Pitch is exactly 25.4/TPI. These basic thread dimensions are separate from process
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bores. The catalogue uses Yamawa's drill column as its default pilot. Its separate
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recommended process-bore references, for the six rows above, are G: 8.78, 11.78,
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15.28, 19.04, 24.52, 30.77 mm and Rp: 8.55, 11.5, 14.9, 18.55, 24.1, 30.25 mm.
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A saved explicit diameter remains authoritative. The geometry stays a physical
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cylindrical pilot plus cosmetic designation, without a helical cut.
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## Primary sources
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- [Yamawa, YEU23 European catalogue](https://www.yamawa.eu/files/Yamawa_European_Catalogue_YEU23.pdf),
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printed page 668: basic G/Rp dimensions; page 707: separate G and Rp drill and
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recommended bore columns. These supply the finite parallel-pipe entries above.
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- [Guhring, Tap Drill Sizes](https://guhring.com/media/catalogs/lgbkp3ieki4.pdf),
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PDF page 2: UNC/UNF pitch and practical CUT TAPS approximately75% drills;
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page 1: decimal equivalents for named drills. The separate FORM TAPS columns
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are not used. Also verifies 14 of the additional metric fine pairs.
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- [PEM, Thread Code Comparison Chart](https://www.pemnet.com/resources/download-center/thread-code-comparison-chart/):
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nominal diameters of #4, #6, #8, #10 and #12 screws.
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- [Yamawa, European catalogue, printed page159](https://www.yamawa.eu/wp-content/uploads/Catalogo_sfogliabile_YEU21/files/basic-html/page161.html):
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M12x1.25 diameter/pitch pair. Its product-specific pilot recommendation is not
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used for the retained metric estimate.
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- [OSG, Tap Drill Sizes and Pitch Diameter Limits, Vol3 (2024)](https://osgtool.com/800274ca-v3/):
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independent cross-check of UNC/UNF pitches. OSG's calculated percentages and
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Guhring's practical named drills are not interchangeable columns.
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## Trial
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On a small plate, open Hole, choose Tapped, then switch Profile between ISO metric,
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UNC, UNF, G / BSPP and Rp. Try M8, M8x1, 1/4-20 UNC, #10-32 UNF, G 1/4
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and Rp 1/4. Check the displayed drill,
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create the hole, save, reopen and check the designation and bore. In ISO metric,
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choose Custom, edit the nominal diameter and pitch, and verify that Custom stays
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selected and an invalid draft cannot apply an earlier valid value.
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