{
 "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": "roller-chain-sprockets",
 "name": "Roller chain sprockets: #25 (6.35 mm) and #35 (9.525 mm), 10–40 T",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Motion",
 "year": null,
 "question": "What is the pitch diameter of a 20 tooth #25 sprocket?",
 "tags": [
  "sprocket",
  "chain",
  "roller chain",
  "drive",
  "motion",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "25 chain sprocket dimensions",
  "#25 chain pitch",
  "35 chain sprocket pd",
  "sprocket pitch diameter formula",
  "roller chain sizes",
  "sprocket stl"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 12,
 "url": "https://xemstudio.com/objects/roller-chain-sprockets/",
 "sheet_txt": "https://xemstudio.com/objects/roller-chain-sprockets/sheet.txt",
 "sheet": {
  "basis": "ANSI B29.1 roller chain: #25 pitch 6.35 mm, roller Ø3.30, width 3.18; #35 pitch 9.525, roller Ø5.08, width 4.78; #40 pitch 12.70, roller Ø7.92. PD = pitch / sin(180°/N), OD ≈ pitch × (0.6 + cot(180°/N))",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "#25 is the small 'bicycle-chain-looking' chain on printers and robots: 6.35 mm (1/4 in) pitch, Ø3.30 rollers, 3.18 mm inner width. #35 is 3/8 in pitch (go-karts, heavier robots). #40 is 1/2 in (bicycles use 1/2 in pitch too but a narrower #410/#415 width).",
   "Pitch diameter = pitch / sin(180°/N): #25 20 T → 40.6 mm; #35 20 T → 60.9 mm. Centre distance between sprockets must put a whole number of links on the chain: L (links) = 2C/p + (N1 + N2)/2 + (N2 − N1)²p/(4π²C); round to an even number.",
   "Tooth profile here is the simple roller-seat form (ANSI 'standard' profile approximated): printed PETG #25 sprockets run fine at model speeds; buy steel for anything over 50 W.",
   "LES: #25 chain from the flywheel to the generator where a belt would slip on a hot shaft; 10 T on the engine, 30 T on the alternator."
  ],
  "table": {
   "columns": [
    "chain",
    "teeth",
    "pitch_dia_mm",
    "od_mm",
    "pitch_mm"
   ],
   "rows": [
    [
     "#25",
     10,
     20.55,
     23.35,
     6.35
    ],
    [
     "#25",
     12,
     24.53,
     27.51,
     6.35
    ],
    [
     "#25",
     15,
     30.54,
     33.68,
     6.35
    ],
    [
     "#25",
     20,
     40.59,
     43.9,
     6.35
    ],
    [
     "#25",
     25,
     50.66,
     54.08,
     6.35
    ],
    [
     "#25",
     30,
     60.75,
     64.23,
     6.35
    ],
    [
     "#25",
     40,
     80.93,
     84.49,
     6.35
    ],
    [
     "#35",
     10,
     30.82,
     35.03,
     9.525
    ],
    [
     "#35",
     12,
     36.8,
     41.26,
     9.525
    ],
    [
     "#35",
     15,
     45.81,
     50.53,
     9.525
    ],
    [
     "#35",
     20,
     60.89,
     65.85,
     9.525
    ],
    [
     "#35",
     30,
     91.12,
     96.34,
     9.525
    ]
   ]
  }
 },
 "sheet_text": "Roller chain sprockets: #25 (6.35 mm) and #35 (9.525 mm), 10–40 T — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/roller-chain-sprockets/  (CC BY 4.0)\nBasis: ANSI B29.1 roller chain: #25 pitch 6.35 mm, roller Ø3.30, width 3.18; #35 pitch 9.525, roller Ø5.08, width 4.78; #40 pitch 12.70, roller Ø7.92. PD = pitch / sin(180°/N), OD ≈ pitch × (0.6 + cot(180°/N))\nCatalog version: 2026-10-20\n\nSizes: see table below\n- #25 is the small 'bicycle-chain-looking' chain on printers and robots: 6.35 mm (1/4 in) pitch, Ø3.30 rollers, 3.18 mm inner width. #35 is 3/8 in pitch (go-karts, heavier robots). #40 is 1/2 in (bicycles use 1/2 in pitch too but a narrower #410/#415 width).\n- Pitch diameter = pitch / sin(180°/N): #25 20 T → 40.6 mm; #35 20 T → 60.9 mm. Centre distance between sprockets must put a whole number of links on the chain: L (links) = 2C/p + (N1 + N2)/2 + (N2 − N1)²p/(4π²C); round to an even number.\n- Tooth profile here is the simple roller-seat form (ANSI 'standard' profile approximated): printed PETG #25 sprockets run fine at model speeds; buy steel for anything over 50 W.\n- LES: #25 chain from the flywheel to the generator where a belt would slip on a hot shaft; 10 T on the engine, 30 T on the alternator.\n\nchain  teeth  pitch_dia_mm  od_mm  pitch_mm\n#25  10  20.55  23.35  6.35\n#25  12  24.53  27.51  6.35\n#25  15  30.54  33.68  6.35\n#25  20  40.59  43.9  6.35\n#25  25  50.66  54.08  6.35\n#25  30  60.75  64.23  6.35\n#25  40  80.93  84.49  6.35\n#35  10  30.82  35.03  9.525\n#35  12  36.8  41.26  9.525\n#35  15  45.81  50.53  9.525\n#35  20  60.89  65.85  9.525\n#35  30  91.12  96.34  9.525\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Roller chain — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Roller_chain\n- McMaster-Carr: Roller chain sprockets (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/roller-chain-sprockets/\n- Wikipedia: Sprocket — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Sprocket\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, 12 parts): https://xemstudio.com/files/hardware/roller-chain-sprockets/index.json\nAPI: https://xemstudio.com/api/geometry?object=roller-chain-sprockets\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Roller chain",
   "url": "https://en.wikipedia.org/wiki/Roller_chain",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Roller chain sprockets (free STEP per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/roller-chain-sprockets/",
   "formats": [
    "STEP",
    "PDF"
   ],
   "license": "McMaster-Carr site terms",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Sprocket",
   "url": "https://en.wikipedia.org/wiki/Sprocket",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "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": [
  "gt2-pulleys",
  "spur-gears-involute",
  "shaft-collars-clips-and-shafts",
  "ball-bearings-metric",
  "axial-flux-generator-kit"
 ],
 "faq": [
  {
   "q": "What is the pitch diameter of a 20 tooth #25 sprocket?",
   "a": "40.64 mm (6.35 / sin 9°); outside diameter about 43.3 mm. A 10 T is 20.55 mm PD."
  },
  {
   "q": "What is the difference between #25 and #35 chain?",
   "a": "Pitch: 6.35 mm vs 9.525 mm; roller Ø3.30 vs Ø5.08; width 3.18 vs 4.78 mm. Sprockets are not interchangeable."
  },
  {
   "q": "How do I calculate chain length?",
   "a": "L = 2C/p + (N1+N2)/2 + (N2−N1)²·p/(4π²·C) links, rounded to an even number; then adjust C so the chain is snug with 2–3% sag."
  }
 ],
 "files_license": null,
 "offers": [
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   "file": "sprocket-25-10t-b8",
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    "step",
    "stl"
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-25-10t-b8.stl",
   "note": "#25 chain (6.35 mm pitch), 10 T, PD 20.55, Ø8 bore hub with M3 set screw"
  },
  {
   "file": "sprocket-25-12t-b8",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-25-12t-b8.stl",
   "note": "#25 chain (6.35 mm pitch), 12 T, PD 24.53, Ø8 bore hub with M3 set screw"
  },
  {
   "file": "sprocket-25-15t-b8",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-25-15t-b8.stl",
   "note": "#25 chain (6.35 mm pitch), 15 T, PD 30.54, Ø8 bore hub with M3 set screw"
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   "file": "sprocket-25-20t-b8",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-25-20t-b8.stl",
   "note": "#25 chain (6.35 mm pitch), 20 T, PD 40.59, Ø8 bore hub with M3 set screw"
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   "file": "sprocket-25-25t-b8",
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   "note": "#25 chain (6.35 mm pitch), 25 T, PD 50.66, Ø8 bore hub with M3 set screw"
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   "file": "sprocket-25-30t-b8",
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   "note": "#25 chain (6.35 mm pitch), 30 T, PD 60.75, Ø8 bore hub with M3 set screw"
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   "file": "sprocket-25-40t-b8",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-35-10t-b8.stl",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-35-12t-b8.stl",
   "note": "#35 chain (9.525 mm pitch), 12 T, PD 36.80, Ø8 bore hub with M3 set screw"
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-35-15t-b8.stl",
   "note": "#35 chain (9.525 mm pitch), 15 T, PD 45.81, Ø8 bore hub with M3 set screw"
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-35-20t-b8.stl",
   "note": "#35 chain (9.525 mm pitch), 20 T, PD 60.89, Ø8 bore hub with M3 set screw"
  },
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   "license": "CC BY 4.0 (Xem Studio)",
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   "stl": "https://xemstudio.com/files/hardware/roller-chain-sprockets/sprocket-35-30t-b8.stl",
   "note": "#35 chain (9.525 mm pitch), 30 T, PD 91.12, Ø8 bore hub with M3 set screw"
  }
 ],
 "markdown": "https://xemstudio.com/objects/roller-chain-sprockets/index.md"
}