{
 "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": "ratchet-wheels",
 "name": "Ratchet wheels Ø40 with 12, 24 and 36 teeth",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "How are the teeth of a ratchet wheel shaped?",
 "tags": [
  "ratchet",
  "one-way",
  "anti-reverse",
  "wheel",
  "mechanism",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "ratchet wheel",
  "ratchet gear stl",
  "ratchet teeth design",
  "anti reverse ratchet",
  "one way ratchet 40mm"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/ratchet-wheels/",
 "sheet_txt": "https://xemstudio.com/objects/ratchet-wheels/sheet.txt",
 "sheet": {
  "basis": "Sawtooth wheel: tips at R20, roots at R17 (3 mm deep), each tooth rising over 85 % of the pitch and dropping over 15 %",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A Ø40 × 6 wheel with a Ø5 bore and 12, 24 or 36 sawtooth teeth 3 mm deep (tips on R20, roots on R17).",
   "Each tooth rises from root to tip over 85 % of the pitch (the back) and drops back over 15 % (the face the pawl locks against).",
   "Steps: 12 teeth 30°, 24 teeth 15°, 36 teeth 10°. Fewer teeth are larger and stronger.",
   "A one-way drive: anti-reverse on a reel, a hand-wound starter, or between a Stirling flywheel and a generator so the generator never back-drives the engine."
  ],
  "table": {
   "columns": [
    "file",
    "teeth",
    "step",
    "tip Ø",
    "root Ø",
    "thickness",
    "bore"
   ],
   "rows": [
    [
     "ratchet-12t-d40",
     12,
     "30°",
     40,
     34,
     6,
     5
    ],
    [
     "ratchet-24t-d40",
     24,
     "15°",
     40,
     34,
     6,
     5
    ],
    [
     "ratchet-36t-d40",
     36,
     "10°",
     40,
     34,
     6,
     5
    ]
   ]
  }
 },
 "sheet_text": "Ratchet wheels Ø40 with 12, 24 and 36 teeth — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/ratchet-wheels/  (CC BY 4.0)\nBasis: Sawtooth wheel: tips at R20, roots at R17 (3 mm deep), each tooth rising over 85 % of the pitch and dropping over 15 %\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A Ø40 × 6 wheel with a Ø5 bore and 12, 24 or 36 sawtooth teeth 3 mm deep (tips on R20, roots on R17).\n- Each tooth rises from root to tip over 85 % of the pitch (the back) and drops back over 15 % (the face the pawl locks against).\n- Steps: 12 teeth 30°, 24 teeth 15°, 36 teeth 10°. Fewer teeth are larger and stronger.\n- A one-way drive: anti-reverse on a reel, a hand-wound starter, or between a Stirling flywheel and a generator so the generator never back-drives the engine.\n\nfile  teeth  step  tip Ø  root Ø  thickness  bore\nratchet-12t-d40  12  30°  40  34  6  5\nratchet-24t-d40  24  15°  40  34  6  5\nratchet-36t-d40  36  10°  40  34  6  5\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Ratchet (device) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Ratchet_(device)\n- Wikipedia: Pawl — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Pawl\n- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/ratchet-wheels/index.json\nAPI: https://xemstudio.com/api/geometry?object=ratchet-wheels\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Ratchet (device)",
   "url": "https://en.wikipedia.org/wiki/Ratchet_(device)",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Pawl",
   "url": "https://en.wikipedia.org/wiki/Pawl",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds that use these parts (videos and write-ups)",
   "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",
  "metric-shafts",
  "spur-gears-involute",
  "torsion-spring"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "metric-shafts",
     "why": "Ø5 shaft in the bore"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "ratchet-pawl",
     "why": "pawl tip against the tooth face"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "torsion-spring",
     "why": "holds the pawl on the teeth"
    }
   ]
  }
 ],
 "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": "wheel bore",
   "exact": "Ø5",
   "mates": "Ø5 shaft",
   "fit": "slide",
   "files": "ratchet-"
  }
 ],
 "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 many teeth should a ratchet have?",
   "a": "12 teeth (30° steps) are the largest and strongest; 24 or 36 give 15° or 10° steps."
  },
  {
   "q": "How deep are the teeth?",
   "a": "3 mm, from R20 at the tips to R17 at the roots."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "ratchet-12t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-12t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-12t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 12 teeth 3 mm deep, Ø5 bore"
  },
  {
   "file": "ratchet-24t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-24t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-24t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 24 teeth 3 mm deep, Ø5 bore"
  },
  {
   "file": "ratchet-36t-d40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-36t-d40.step",
   "stl": "https://xemstudio.com/files/hardware/ratchet-and-pawl/ratchet-36t-d40.stl",
   "note": "ratchet wheel Ø40 × 6, 36 teeth 3 mm deep, Ø5 bore"
  }
 ],
 "markdown": "https://xemstudio.com/objects/ratchet-wheels/index.md"
}