{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "face-spiral-wheel-m1-5-24t-for-scroll-r39",
 "name": "Wheel for a face spiral, module 1.5, 24 teeth, generated by the scroll at radius 39",
 "kind": "modern",
 "category": "Mechanisms",
 "group": "Gears",
 "year": null,
 "question": "What wheel runs on a face spiral?",
 "tags": [
  "mechanism part",
  "507 mechanical movements"
 ],
 "aliases": [
  "face spiral wheel",
  "scroll wheel",
  "generated spur wheel",
  "rueda para espiral frontal",
  "Rad für Spiralscheibe"
 ],
 "overall_mm": {
  "length": 38.85,
  "width": 38.85,
  "height": 8
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/face-spiral-wheel-m1-5-24t-for-scroll-r39/",
 "sheet_txt": "https://xemstudio.com/objects/face-spiral-wheel-m1-5-24t-for-scroll-r39/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown's figure (1868); true size, no printing allowance",
  "overall_mm": {
   "length": 38.85,
   "width": 38.85,
   "height": 8
  },
  "notes": [
   "24-tooth wheel of module 1.5 (pitch Ø36, tip Ø39, root Ø32.25, 8 mm face, Ø6 bore) whose teeth were generated by the spiral rib itself: in every plane across the face the rib's section (a rack tooth that is slightly wider and farther out away from the disc's centre line) was swept past the turning wheel and the envelope taken, then the seven sections lofted (spline fit within 0.108 mm). The result is an involute-like tooth that is very slightly curved and thinner across the face — the exact mate of the rib at radius 39, where a plain straight spur gear would bind at the face edges.",
   "One tooth per turn of the disc; the wheel's axis lies parallel to the disc face, tangent to the spiral at the mesh.",
   "Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features)."
  ],
  "table": {
   "columns": [
    "dimension",
    "value"
   ],
   "rows": [
    [
     "module",
     "1.5"
    ],
    [
     "teeth",
     "24"
    ],
    [
     "pitch Ø",
     "36 mm"
    ],
    [
     "tip / root Ø",
     "39 / 32.25 mm"
    ],
    [
     "face",
     "8 mm"
    ],
    [
     "bore",
     "Ø6"
    ],
    [
     "mesh radius on the disc",
     "39 mm"
    ]
   ]
  }
 },
 "sheet_text": "Wheel for a face spiral, module 1.5, 24 teeth, generated by the scroll at radius 39 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/face-spiral-wheel-m1-5-24t-for-scroll-r39/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Xem Studio design following Brown's figure (1868); true size, no printing allowance\nCatalog version: 2026-10-20\n\nOverall (mm): length 38.85, width 38.85, height 8.0\n- 24-tooth wheel of module 1.5 (pitch Ø36, tip Ø39, root Ø32.25, 8 mm face, Ø6 bore) whose teeth were generated by the spiral rib itself: in every plane across the face the rib's section (a rack tooth that is slightly wider and farther out away from the disc's centre line) was swept past the turning wheel and the envelope taken, then the seven sections lofted (spline fit within 0.108 mm). The result is an involute-like tooth that is very slightly curved and thinner across the face — the exact mate of the rib at radius 39, where a plain straight spur gear would bind at the face edges.\n- One tooth per turn of the disc; the wheel's axis lies parallel to the disc face, tangent to the spiral at the mesh.\n- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).\n\ndimension  value\nmodule  1.5\nteeth  24\npitch Ø  36 mm\ntip / root Ø  39 / 32.25 mm\nface  8 mm\nbore  Ø6\nmesh radius on the disc  39 mm\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala\n- 507movements.com: Brown's movement No. 29: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_029.html\n- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/face-spiral-disc-and-wheel-mechanism/\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/face-spiral-wheel-m1-5-24t-for-scroll-r39/index.json\nAPI: https://xemstudio.com/api/geometry?object=face-spiral-wheel-m1-5-24t-for-scroll-r39\n",
 "sources": [
  {
   "publisher": "Henry T. Brown (1868, public domain)",
   "title": "Five Hundred and Seven Mechanical Movements — scan on archive.org",
   "url": "https://archive.org/details/fivehundredseven00browiala",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "507movements.com",
   "title": "Brown's movement No. 29: figure, his text and an animation",
   "url": "https://507movements.com/mm_029.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Xem Studio",
   "title": "drawing",
   "url": "https://xemstudio.com/objects/face-spiral-disc-and-wheel-mechanism/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "face-spiral-disc-and-wheel-mechanism"
 ],
 "fits": [],
 "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": [],
 "faq": [
  {
   "q": "What wheel runs on a face spiral?",
   "a": "24-tooth wheel of module 1.5 (pitch Ø36, tip Ø39, root Ø32.25, 8 mm face, Ø6 bore) whose teeth were generated by the spiral rib itself: in every plane across the face the rib's section (a rack tooth that is slightly wider and farther out away from the disc's centre line) was swept past the turning wheel and the envelope taken, then the seven sections lofted (spline fit within 0.108 mm). The result is an involute-like tooth that is very slightly curved and thinner across the face — the exact mate of the rib at radius 39, where a plain straight spur gear would bind at the face edges."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
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   "file": "face-spiral-wheel-m1-5-24t-for-scroll-r39",
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    "stl"
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   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/face-spiral-wheel-m1-5-24t-for-scroll-r39/face-spiral-wheel-m1-5-24t-for-scroll-r39.step",
   "stl": "https://xemstudio.com/files/hardware/face-spiral-wheel-m1-5-24t-for-scroll-r39/face-spiral-wheel-m1-5-24t-for-scroll-r39.stl",
   "note": "wheel, axis Z, z -4..4, a space centred on +X"
  }
 ],
 "markdown": "https://xemstudio.com/objects/face-spiral-wheel-m1-5-24t-for-scroll-r39/index.md"
}