{
 "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": "double-helical-gear-mn1-5-30t-beta20-bore8",
 "name": "Double-helical (herringbone) gear, normal module 1.5, 30 teeth, helix 20° , face 16, Ø8 bore",
 "kind": "modern",
 "category": "Hardware",
 "group": "Mechanism parts",
 "year": null,
 "question": "What are the dimensions of a 30-tooth, 20° double-helical (herringbone) gear?",
 "tags": [
  "mechanism part",
  "507 mechanical movements"
 ],
 "aliases": [
  "herringbone gear",
  "double helical gear",
  "engranaje bihelicoidal (espina de pescado)",
  "Pfeilzahnrad"
 ],
 "overall_mm": {
  "length": 50.89,
  "width": 50.89,
  "height": 16
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/double-helical-gear-mn1-5-30t-beta20-bore8/",
 "sheet_txt": "https://xemstudio.com/objects/double-helical-gear-mn1-5-30t-beta20-bore8/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown's figure (1868); true size, no printing allowance",
  "overall_mm": {
   "length": 50.89,
   "width": 50.89,
   "height": 16
  },
  "notes": [
   "Normal module 1.5, helix angle 20°: transverse module 1.6, transverse pressure angle 21.17°, pitch Ø47.89, tip Ø50.89, root Ø44.14; addendum 1.5, dedendum 1.88 (normal-module depths).",
   "Two opposed 20° helices meet at mid-face (twist 6.97° each way over 8 mm), so the end thrusts cancel.",
   "Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features)."
  ],
  "table": {
   "columns": [
    "dimension",
    "value"
   ],
   "rows": [
    [
     "normal module",
     "1.5"
    ],
    [
     "teeth",
     "30"
    ],
    [
     "helix angle",
     "20°"
    ],
    [
     "transverse module",
     "1.6"
    ],
    [
     "pitch Ø",
     "47.89 mm"
    ],
    [
     "tip Ø",
     "50.89 mm"
    ],
    [
     "face",
     "16 mm"
    ],
    [
     "bore",
     "Ø8"
    ]
   ]
  }
 },
 "sheet_text": "Double-helical (herringbone) gear, normal module 1.5, 30 teeth, helix 20° , face 16, Ø8 bore — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/double-helical-gear-mn1-5-30t-beta20-bore8/  (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 50.89, width 50.89, height 16.0\n- Normal module 1.5, helix angle 20°: transverse module 1.6, transverse pressure angle 21.17°, pitch Ø47.89, tip Ø50.89, root Ø44.14; addendum 1.5, dedendum 1.88 (normal-module depths).\n- Two opposed 20° helices meet at mid-face (twist 6.97° each way over 8 mm), so the end thrusts cancel.\n- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).\n\ndimension  value\nnormal module  1.5\nteeth  30\nhelix angle  20°\ntransverse module  1.6\npitch Ø  47.89 mm\ntip Ø  50.89 mm\nface  16 mm\nbore  Ø8\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. 41: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_041.html\n- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/double-helical-gears-mechanism/\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/double-helical-gear-mn1-5-30t-beta20-bore8/index.json\nAPI: https://xemstudio.com/api/geometry?object=double-helical-gear-mn1-5-30t-beta20-bore8\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. 41: figure, his text and an animation",
   "url": "https://507movements.com/mm_041.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/double-helical-gears-mechanism/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
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  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "double-helical-gears-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 are the dimensions of a 30-tooth, 20° double-helical (herringbone) gear?",
   "a": "Normal module 1.5, helix angle 20°: transverse module 1.6, transverse pressure angle 21.17°, pitch Ø47.89, tip Ø50.89, root Ø44.14; addendum 1.5, dedendum 1.88 (normal-module depths)."
  }
 ],
 "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."
 },
 "offers": [
  {
   "file": "double-helical-gear-mn1-5-30t-beta20-bore8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/double-helical-gear-mn1-5-30t-beta20-bore8/double-helical-gear-mn1-5-30t-beta20-bore8.step",
   "stl": "https://xemstudio.com/files/hardware/double-helical-gear-mn1-5-30t-beta20-bore8/double-helical-gear-mn1-5-30t-beta20-bore8.stl",
   "note": "gear, axis Z, z 0..16, a tooth on +X at z = 0"
  }
 ],
 "markdown": "https://xemstudio.com/objects/double-helical-gear-mn1-5-30t-beta20-bore8/index.md"
}