{"$schema":"nativecad-dfm-pack/1","id":"jewellery-wearables","title":"Jewellery & wearables — rings, pendants, bracelets, watches, glasses","sector":"jewellery-wearables","version":"2026-09-04","summary":"Ring sizing (ISO 8653 and US/UK), band and bezel dimensions, prong and bezel settings, bangle/bracelet/pendant-bail sizing, watch case and strap dimensions, eyeglass frame box-system numbers, casting/DMLS processes, metal densities and the nickel-release, retention and drop tests jewellery and wearables are held to.","aliases":["ring","signet ring","wedding band","bracelet","bangle","cuff","pendant","necklace","earring","stud earring","watch case","watch strap","lug","glasses","eyeglass frame","sunglasses","jewelry","jewellery","brooch","cufflink","charm","bail"],"crossSector":false,"size":"core","sources":[{"id":"iso-8653","title":"ISO 8653:2016 Ring-sizes","url":"https://www.iso.org/standard/65408.html","accessed":"2026-09-04"},{"id":"en-1811","title":"EN 1811:2023 Nickel release test method","url":"https://standards.iteh.ai/catalog/standards/cen/6692f2c9-c4b6-4539-a4d3-17611e1acdbc/en-1811-2023","accessed":"2026-09-04"},{"id":"iso-12870","title":"ISO 12870 Spectacle frames — requirements/tests","url":"https://www.iso.org/search.html?q=ISO%2012870","accessed":"2026-09-04"},{"id":"iso-8624","title":"ISO 8624 Spectacle frames — box system","url":"https://www.iso.org/search.html?q=ISO%208624","accessed":"2026-09-04"},{"id":"materialise-gold-guide","title":"Materialise gold lost-wax casting guide","url":"https://www.materialise.com/en/academy/industrial/design-am/gold","accessed":"2026-09-04"},{"id":"ganoksin-casting","title":"Ganoksin — casting shrinkage/shop practice","url":"https://orchid.ganoksin.com/t/casting-shrinkage/48368","accessed":"2026-09-04"},{"id":"nihs-spring-bar","title":"NIHS 37-01 spring-bar diameters","url":"https://pompe-de-montre.com/en/content/16-measuring-watch-spring-bar","accessed":"2026-09-04"},{"id":"watch-lug-guide","title":"Watch lug-width sizing convention","url":"https://www.hewore.com/watch-lug-width-guide/","accessed":"2026-09-04"},{"id":"gia-diamond-sizes","title":"GIA diamond mm-to-carat chart","url":"https://www.gia.edu/gia-news-research/diamond-size-chart","accessed":"2026-09-04"}],"entries":[{"id":"ring-size-us-uk-table","kind":"dimension","tier":1,"title":"US/UK ring size to inner diameter and circumference","summary":"US size 7 (UK N, EU 54) = 17.3 mm inner diameter / 54.4 mm circumference; each US half-size steps about 0.4 mm in diameter, e.g. US 6 = 16.5 mm ID, US 8 = 18.1 mm ID.","applies":["ring","signet ring","wedding band"],"value":{"table":[{"usSize":5,"idMm":15.7,"circumferenceMm":49.3},{"usSize":6,"idMm":16.5,"circumferenceMm":51.9},{"usSize":7,"idMm":17.3,"circumferenceMm":54.4},{"usSize":8,"idMm":18.1,"circumferenceMm":57},{"usSize":9,"idMm":18.9,"circumferenceMm":59.5},{"usSize":10,"idMm":19.8,"circumferenceMm":62.1}],"unit":"mm"},"basis":"ISO 8653 circumference table cross-referenced to the US/UK jeweller sizing convention","sources":["iso-8653"],"tags":["ring","sizing","us","uk"]},{"id":"band-width-range","kind":"dimension","tier":1,"title":"Ring band width","summary":"A ring band runs 2-8 mm wide (axial length along the finger); 2-3 mm reads as a stacking/eternity band, 5-6 mm as a standard wedding band, 7-8 mm as a chunky signet or men's band.","applies":["ring","wedding band","signet ring"],"value":{"min":2,"max":8,"typical":5,"unit":"mm"},"basis":"Common jeweller band-width range balancing comfort against visual weight for the stated ring classes","sources":["iso-8653"],"tags":["ring","band","width"]},{"id":"band-thickness-by-process","kind":"dimension","tier":1,"title":"Ring band radial thickness by process","summary":"Size a band's radial (wall) thickness at >=1.2 mm for cast gold, >=1.5 mm for cast/fabricated silver, and >=2 mm for a 3D-printed (resin-to-cast or DMLS) band, since each process's own minimum-section floor is what actually limits it.","applies":["ring","wedding band","signet ring"],"value":{"table":[{"process":"cast-gold","minMm":1.2},{"process":"cast-silver","minMm":1.5},{"process":"printed","minMm":2}],"unit":"mm"},"basis":"Gold's higher density and fluidity lets a cast band run thinner than silver at the same strength; a printed/print-and-cast band needs the extra margin the additive process's own minimum wall imposes","sources":["materialise-gold-guide","ganoksin-casting"],"tags":["ring","band","thickness","wall"]},{"id":"comfort-fit-inner-radius","kind":"rule","tier":1,"title":"Comfort-fit inner profile","summary":"A comfort-fit band rounds its inner bore to a radius roughly equal to the band's own radial thickness (1.2-2 mm), domed rather than flat, so the ring rocks past a knuckle instead of catching its full flat width on the skin.","applies":["ring","wedding band"],"value":{"min":1.2,"max":2,"unit":"mm"},"basis":"A domed inner profile reduces the ring's effective bearing width against the finger to roughly its thickness rather than its full band width, which is what a wearer feels as comfort fit","sources":["iso-8653"],"tags":["ring","comfort-fit","ergonomics"]},{"id":"prong-setting-basics","kind":"feature","tier":1,"title":"Prong count and prong-tip sizing for a stone setting","summary":"Use 4 prongs for a square/princess stone and 6 prongs for a round stone >=5 mm; each prong tip runs 0.8-1.2 mm square before it is filed down over the stone's girdle, thick enough to hold but thin enough not to hide the stone.","applies":["ring","pendant","prong setting"],"value":{"min":0.8,"max":1.2,"unit":"mm"},"basis":"Fewer, wider prongs suit a squared stone's flat girdle edges; a round stone's continuous girdle is held more securely by more, narrower prongs distributing load evenly","sources":["gia-diamond-sizes"],"tags":["ring","prong","setting","stone"]},{"id":"bezel-wall-thickness","kind":"dimension","tier":1,"title":"Bezel setting wall thickness","summary":"A metal bezel wrapping a stone's girdle runs 0.5-0.8 mm thick before burnishing over the stone; thinner tears when pushed over the girdle, thicker looks heavy and needs more force to set.","applies":["ring","pendant","bezel setting"],"value":{"min":0.5,"max":0.8,"unit":"mm"},"basis":"The bezel wall must be thin enough to burnish (cold-flow) over the stone's girdle by hand or with a bezel roller, but thick enough not to split while doing so","sources":["materialise-gold-guide"],"tags":["bezel","setting","wall"]},{"id":"bangle-id-oval","kind":"dimension","tier":1,"title":"Bangle inner diameter, oval opening","summary":"A rigid bangle needs a 60-70 mm oval inner opening (measured across the long axis, ~5-8 mm narrower on the short axis) to pass over an adult hand; a hinged bangle can drop the long axis toward 55 mm.","applies":["bangle","bracelet"],"value":{"min":60,"max":70,"typical":65,"unit":"mm"},"basis":"The oval opening must clear the widest part of an adult hand (the metacarpals) on the long axis while sitting close on the wrist once past the knuckles","sources":["iso-8653"],"tags":["bangle","sizing","oval"]},{"id":"bracelet-length-range","kind":"dimension","tier":1,"title":"Chain/flexible bracelet length","summary":"A flexible chain or bead bracelet runs 170-190 mm finished length for an adult wrist, plus 20-40 mm of clasp/extender adjustment; a men's bracelet sits at the upper end, a petite/child size below 170 mm.","applies":["bracelet","cuff"],"value":{"min":170,"max":190,"typical":180,"unit":"mm"},"basis":"Standard adult wrist circumference range plus the drape allowance a chain or bead bracelet needs to sit rather than bind","sources":["iso-8653"],"tags":["bracelet","sizing","length"]},{"id":"earring-post-dimensions","kind":"dimension","tier":1,"title":"Stud earring post diameter and length","summary":"A stud earring post runs 0.8 mm diameter x 10 mm long, sized to pass a standard pierced lobe and take a friction (butterfly) back with 2-4 mm of travel before it seats.","applies":["earring","stud earring"],"value":{"table":[{"param":"diameter","value":0.8},{"param":"length","value":10}],"unit":"mm"},"basis":"0.8 mm is the de-facto standard post gauge sized to a standard ear-piercing gun/needle bore, with 10 mm long enough to clear most lobe thicknesses plus the butterfly back","sources":["en-1811"],"tags":["earring","post","butterfly-back"]},{"id":"pendant-bail-clearance-rule","kind":"rule","tier":1,"title":"Pendant bail inner diameter vs chain gauge","summary":"Size a pendant bail's inner diameter to at least the chain's wire diameter plus 1 mm, so the chain articulates freely through the bail instead of binding or wearing a flat spot into the link.","applies":["pendant","bail","charm","necklace"],"value":{"min":1,"unit":"mm","note":"bail ID >= chain wire diameter + 1mm"},"basis":"A bail sized only to the chain's own diameter binds under normal articulation; the 1 mm margin is what lets the chain pivot instead of dragging metal-on-metal at one contact line","sources":["iso-8653"],"tags":["pendant","bail","chain","clearance"]},{"id":"watch-case-lug-width","kind":"dimension","tier":1,"title":"Watch case lug width","summary":"Watch straps come in 18, 20 or 22 mm lug width, matching the gap between the case's lug horns; 20 mm is the most common size across men's watches, with 18 mm skewing smaller/women's and 22-24 mm sport/diver cases.","applies":["watch case","watch strap","lug"],"value":{"options":[18,20,22,24],"unit":"mm"},"basis":"Industry lug-width convention that a strap and its spring bars must match to fit a given case","sources":["watch-lug-guide"],"tags":["watch","lug","strap","sizing"]},{"id":"watch-case-diameter-range","kind":"dimension","tier":1,"title":"Watch case diameter","summary":"A wristwatch case runs 36-44 mm in diameter (excluding crown), with 40-42 mm the most common men's size and 36-38 mm reading as a smaller/unisex case; the case diameter also sets the lug-to-lug envelope for wrist fit.","applies":["watch case"],"value":{"min":36,"max":44,"typical":40,"unit":"mm"},"basis":"Common modern wristwatch case-diameter range across men's and unisex sport/dress designs","sources":["watch-lug-guide"],"tags":["watch","case","diameter"]},{"id":"watch-spring-bar-hole","kind":"dimension","tier":1,"title":"Spring bar hole diameter in a lug","summary":"Bore the spring-bar hole through each lug at 1.2-1.5 mm diameter (standard spring bars run 1.0/1.2/1.3/1.5/1.8 mm), with a +-0.2 mm functional tolerance so the bar seats without slop or binding.","applies":["watch case","lug"],"value":{"min":1.2,"max":1.5,"unit":"mm"},"basis":"Spring bars are made in a small set of standard diameters; the lug hole must match one of them within a tight functional tolerance to hold the bar under spring load","sources":["nihs-spring-bar"],"tags":["watch","spring-bar","lug","hole"]},{"id":"glasses-box-system","kind":"dimension","tier":1,"title":"Eyeglass frame box-system callout (e.g. 52-18-140)","summary":"A frame is specified as lens-width–bridge–temple in mm, e.g. 52-18-140: 52 mm horizontal lens width, 18 mm bridge gap between lenses, 140 mm temple arm length from hinge to tip.","applies":["glasses","eyeglass frame","sunglasses"],"value":{"table":[{"param":"lens-width","typical":52},{"param":"bridge","typical":18},{"param":"temple","typical":140}],"unit":"mm"},"basis":"ISO 8624 box (boxing) system measures each lens as if boxed in a rectangle, giving three numbers that fully describe a frame's fit envelope","sources":["iso-8624"],"tags":["glasses","box-system","sizing"]},{"id":"glasses-hinge-screw","kind":"dimension","tier":1,"title":"Eyeglass hinge screw diameter","summary":"A spectacle hinge barrel takes a 1.2-1.6 mm screw through 2-3 knuckles; undersize and the hinge racks loose in weeks, oversize and the barrel wall splits on tightening.","applies":["glasses","eyeglass frame"],"value":{"min":1.2,"max":1.6,"unit":"mm"},"basis":"Standard spectacle-hinge screw gauge sized to the thin metal or acetate barrel wall a temple hinge is built into","sources":["iso-12870"],"tags":["glasses","hinge","screw"]},{"id":"glasses-pantoscopic-tilt","kind":"rule","tier":1,"title":"Pantoscopic tilt of the lens plane","summary":"Tilt the lens plane 8-12 degrees forward at the bottom (pantoscopic tilt) relative to vertical, so the lens sits roughly perpendicular to the wearer's downward gaze rather than straight-on.","applies":["glasses","eyeglass frame","sunglasses"],"value":{"min":8,"max":12,"unit":"deg"},"basis":"Matching the lens plane to habitual downward gaze angle reduces off-axis optical distortion for progressive and single-vision lenses alike","sources":["iso-12870"],"tags":["glasses","tilt","ergonomics"]},{"id":"casting-min-wall-no-voids","kind":"rule","tier":1,"title":"Lost-wax casting minimum wall and enclosed voids","summary":"Keep every cast section >=0.6 mm and never fully enclose a void: the investment plaster fills every internal cavity during burnout and cannot be removed from a sealed pocket, so a hollow form needs a vent/access hole before casting.","applies":["ring","pendant","casting"],"value":{"min":0.6,"unit":"mm"},"basis":"Below ~0.6 mm the wax pattern itself is too fragile to invest and the molten metal freezes before filling the section; a sealed cavity traps investment that cannot be devested afterward","sources":["materialise-gold-guide","ganoksin-casting"],"tags":["casting","lost-wax","wall","void"]},{"id":"nickel-release-en1811","kind":"test","tier":1,"title":"Nickel release test for skin-contact jewellery (EN 1811)","summary":"EN 1811 limits nickel release to 0.5 ug/cm2/week for rings, bracelets and watch cases, and 0.2 ug/cm2/week for a post inserted into a piercing; failing it means re-specifying the alloy (nickel-free white gold, titanium, 316L), not changing geometry.","applies":["ring","earring","bracelet","watch case"],"value":{"min":0.2,"max":0.5,"unit":"ratio","note":"ug/cm2/week; 0.2 for pierced posts, 0.5 for general skin-contact"},"basis":"EN 1811 sets the EU REACH nickel-release migration limit, tested by immersion in artificial sweat solution, tighter for articles inserted into a piercing than for general skin contact","sources":["en-1811"],"tags":["test","nickel","hypoallergenic","en1811"]}]}