{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "torsion-spring",
 "name": "Torsion spring wire Ø0.8, OD 8, 6 coils",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Motion",
 "year": null,
 "question": "What are the dimensions of a small torsion spring?",
 "tags": [
  "torsion spring",
  "spring",
  "pawl spring",
  "return spring",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "torsion spring design",
  "torsion spring dimensions",
  "small torsion spring step",
  "pawl return spring"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/torsion-spring/",
 "sheet_txt": "https://xemstudio.com/objects/torsion-spring/sheet.txt",
 "sheet": {
  "basis": "Close-wound helical torsion spring with two straight tangential legs; rate E d⁴ / (3667 D n) N·mm per degree",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Six close-wound coils of 0.8 wire, OD 8, ID 6.4, with two straight legs reaching 10 mm from the coil axis. Envelope 14 × 8 × 5.7.",
   "Torsion rate in N·mm per degree = E d⁴ / (3667 D n), E the wire's elastic modulus, D the mean Ø (7.2), n the coils.",
   "The ID (6.4) goes over an arbor; the legs bear on the two parts it sets against each other, such as a pawl and its frame."
  ],
  "table": {
   "columns": [
    "feature",
    "value_mm"
   ],
   "rows": [
    [
     "wire Ø",
     0.8
    ],
    [
     "OD / ID",
     "8 / 6.4"
    ],
    [
     "coils",
     6
    ],
    [
     "leg reach from axis",
     10
    ],
    [
     "envelope",
     "14 × 8 × 5.7"
    ]
   ]
  }
 },
 "sheet_text": "Torsion spring wire Ø0.8, OD 8, 6 coils — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/torsion-spring/  (CC BY 4.0)\nBasis: Close-wound helical torsion spring with two straight tangential legs; rate E d⁴ / (3667 D n) N·mm per degree\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Six close-wound coils of 0.8 wire, OD 8, ID 6.4, with two straight legs reaching 10 mm from the coil axis. Envelope 14 × 8 × 5.7.\n- Torsion rate in N·mm per degree = E d⁴ / (3667 D n), E the wire's elastic modulus, D the mean Ø (7.2), n the coils.\n- The ID (6.4) goes over an arbor; the legs bear on the two parts it sets against each other, such as a pawl and its frame.\n\nfeature  value_mm\nwire Ø  0.8\nOD / ID  8 / 6.4\ncoils  6\nleg reach from axis  10\nenvelope  14 × 8 × 5.7\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Spring (device) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Spring_(device)\n- McMaster-Carr: Compression springs (free STEP per part, for your own design use; no redistribution) — STEP, PDF — McMaster-Carr site terms [verify license at link] — https://www.mcmaster.com/products/compression-springs/\n- Lee Spring: Spring design formulas — web — Lee Spring site [verify license at link] — https://www.leespring.com/learn-about-springs\n- Long Earth Society: Engine and rig builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/torsion-spring/index.json\nAPI: https://xemstudio.com/api/geometry?object=torsion-spring\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Spring (device)",
   "url": "https://en.wikipedia.org/wiki/Spring_(device)",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Compression springs (free STEP per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/compression-springs/",
   "formats": [
    "STEP",
    "PDF"
   ],
   "license": "McMaster-Carr site terms",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Lee Spring",
   "title": "Spring design formulas",
   "url": "https://www.leespring.com/learn-about-springs",
   "formats": [
    "web"
   ],
   "license": "Lee Spring site",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine and rig builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "ratchet-pawl",
  "compression-springs",
  "extension-springs"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "ratchet-pawl",
     "why": "holds the pawl on the teeth"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "compression-springs",
     "why": "linear return"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "spring OD",
   "exact": "OD (6–16)",
   "mates": "pocket of the same Ø",
   "fit": "socket",
   "files": "all"
  },
  {
   "feature": "spring ID",
   "exact": "OD − 2 × wire",
   "mates": "guide rod or arbor of the same Ø",
   "fit": "socket",
   "files": "all"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "How do I calculate a torsion spring rate?",
   "a": "N·mm per degree = E·d⁴ / (3667·D·n), with D the mean coil Ø and n the coils."
  },
  {
   "q": "What arbor fits the torsion spring?",
   "a": "The coil ID is 6.4."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "torsion-d0.8-od8-l10",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/springs/torsion-d0.8-od8-l10.step",
   "stl": "https://xemstudio.com/files/hardware/springs/torsion-d0.8-od8-l10.stl",
   "note": "torsion spring envelope: wire Ø0.8, OD 8, ID 6.4, legs reaching 10 mm from the axis, 6 coils"
  }
 ],
 "markdown": "https://xemstudio.com/objects/torsion-spring/index.md"
}