{
 "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": "stirling-crankshafts",
 "name": "Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What crankshaft sizes fit the 623, 625 and 608 bearings on a model Stirling engine?",
 "tags": [
  "crankshaft",
  "shaft",
  "d-flat",
  "stirling",
  "623",
  "625",
  "608",
  "long earth society"
 ],
 "aliases": [
  "stirling engine crankshaft",
  "5mm d shaft full length",
  "8mm crankshaft",
  "model engine crankshaft step",
  "3mm crankshaft"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 11,
 "url": "https://xemstudio.com/objects/stirling-crankshafts/",
 "sheet_txt": "https://xemstudio.com/objects/stirling-crankshafts/sheet.txt",
 "sheet": {
  "basis": "Solid shafts at the 623 / 625 / 608 bore Ø; Ø5 and Ø8 with a 0.5 mm D-flat along the whole length",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Solid round shafts with 0.3 chamfers on both ends. Ø3 × 40, 44, 60 and 80 are plain round; Ø5 × 80, 100, 120, 150 and Ø8 × 80, 100, 120 have a D-flat 0.5 deep along the whole length (4.5 and 7.5 across the flat).",
   "The flat is where the M3 grubs in crank discs, webs and flywheel hubs bear, so the hubs cannot turn on the shaft. It also gives the shaft a flat face to lie on.",
   "Ø3: the crank head's 623 towers and the Ø3-bore crank discs. Ø5: the 625 crank stands, rhombic gears, crank discs and Ø5 flywheel hubs. Ø8: the tri-clamp crank frame's 608s, crank webs and Ø8 flywheel hubs.",
   "Lengths on the engines here: 2 in gamma Ø5 × 100 between two 625 stands with the flywheel outside; tri-clamp crank frame Ø8 × 80; rhombic gear shafts Ø5 × 80, one × 120 to carry the flywheel; can engine Ø3 × 44 and LTD Ø3 × 40 (a crank disc at each end, bearings and flywheel between)."
  ],
  "table": {
   "columns": [
    "file",
    "Ø",
    "length",
    "D-flat",
    "fits"
   ],
   "rows": [
    [
     "crankshaft-3x40",
     3,
     40,
     "—",
     "623; crank-disc-b3"
    ],
    [
     "crankshaft-3x44",
     3,
     44,
     "—",
     "623; crank-disc-b3"
    ],
    [
     "crankshaft-3x60",
     3,
     60,
     "—",
     "623; crank-disc-b3"
    ],
    [
     "crankshaft-3x80",
     3,
     80,
     "—",
     "623; crank-disc-b3"
    ],
    [
     "crankshaft-5x80-dflat",
     5,
     80,
     "0.5 full length (4.5)",
     "625; crank discs; Ø5 hubs"
    ],
    [
     "crankshaft-5x100-dflat",
     5,
     100,
     "0.5 full length (4.5)",
     "625; crank discs; Ø5 hubs"
    ],
    [
     "crankshaft-5x120-dflat",
     5,
     120,
     "0.5 full length (4.5)",
     "625; crank discs; Ø5 hubs"
    ],
    [
     "crankshaft-5x150-dflat",
     5,
     150,
     "0.5 full length (4.5)",
     "625; crank discs; Ø5 hubs"
    ],
    [
     "crankshaft-8x80-dflat",
     8,
     80,
     "0.5 full length (7.5)",
     "608; crank webs; Ø8 hubs"
    ],
    [
     "crankshaft-8x100-dflat",
     8,
     100,
     "0.5 full length (7.5)",
     "608; crank webs; Ø8 hubs"
    ],
    [
     "crankshaft-8x120-dflat",
     8,
     120,
     "0.5 full length (7.5)",
     "608; crank webs; Ø8 hubs"
    ]
   ]
  }
 },
 "sheet_text": "Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/stirling-crankshafts/  (CC BY 4.0)\nBasis: Solid shafts at the 623 / 625 / 608 bore Ø; Ø5 and Ø8 with a 0.5 mm D-flat along the whole length\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Solid round shafts with 0.3 chamfers on both ends. Ø3 × 40, 44, 60 and 80 are plain round; Ø5 × 80, 100, 120, 150 and Ø8 × 80, 100, 120 have a D-flat 0.5 deep along the whole length (4.5 and 7.5 across the flat).\n- The flat is where the M3 grubs in crank discs, webs and flywheel hubs bear, so the hubs cannot turn on the shaft. It also gives the shaft a flat face to lie on.\n- Ø3: the crank head's 623 towers and the Ø3-bore crank discs. Ø5: the 625 crank stands, rhombic gears, crank discs and Ø5 flywheel hubs. Ø8: the tri-clamp crank frame's 608s, crank webs and Ø8 flywheel hubs.\n- Lengths on the engines here: 2 in gamma Ø5 × 100 between two 625 stands with the flywheel outside; tri-clamp crank frame Ø8 × 80; rhombic gear shafts Ø5 × 80, one × 120 to carry the flywheel; can engine Ø3 × 44 and LTD Ø3 × 40 (a crank disc at each end, bearings and flywheel between).\n\nfile  Ø  length  D-flat  fits\ncrankshaft-3x40  3  40  —  623; crank-disc-b3\ncrankshaft-3x44  3  44  —  623; crank-disc-b3\ncrankshaft-3x60  3  60  —  623; crank-disc-b3\ncrankshaft-3x80  3  80  —  623; crank-disc-b3\ncrankshaft-5x80-dflat  5  80  0.5 full length (4.5)  625; crank discs; Ø5 hubs\ncrankshaft-5x100-dflat  5  100  0.5 full length (4.5)  625; crank discs; Ø5 hubs\ncrankshaft-5x120-dflat  5  120  0.5 full length (4.5)  625; crank discs; Ø5 hubs\ncrankshaft-5x150-dflat  5  150  0.5 full length (4.5)  625; crank discs; Ø5 hubs\ncrankshaft-8x80-dflat  8  80  0.5 full length (7.5)  608; crank webs; Ø8 hubs\ncrankshaft-8x100-dflat  8  100  0.5 full length (7.5)  608; crank webs; Ø8 hubs\ncrankshaft-8x120-dflat  8  120  0.5 full length (7.5)  608; crank webs; Ø8 hubs\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 11 parts): https://xemstudio.com/files/hardware/stirling-crankshafts/index.json\nAPI: https://xemstudio.com/api/geometry?object=stirling-crankshafts\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Engine 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": [
  "metric-shafts",
  "crank-discs-5mm-bore",
  "crank-stands-625",
  "nut-pocket-flywheels",
  "shaft-spacers",
  "ball-bearings-metric"
 ],
 "fits": [
  {
   "role": "Parts that fit it",
   "items": [
    {
     "slug": "scotch-yoke",
     "why": "crank disc on a Ø5 shaft"
    },
    {
     "slug": "geneva-drive",
     "why": "Ø5 shafts for wheel and drive"
    },
    {
     "slug": "spoked-flywheels",
     "why": "Ø5 / Ø8 bore, M3 grub on the flat"
    },
    {
     "slug": "counterweighted-crank-discs",
     "why": "Ø5 bore, M3 grub on the flat"
    },
    {
     "slug": "crank-webs-5mm-bore",
     "why": "Ø5 bore, M3 grub"
    },
    {
     "slug": "shaft-adapter-5-to-8mm",
     "why": "Ø5 bore on the D-flat shaft"
    },
    {
     "slug": "crank-discs-3mm-bore",
     "why": "Ø3 crankshaft in the bore"
    }
   ]
  },
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "crank-stands-625",
     "why": "Ø5 shaft in the stands' 625s"
    },
    {
     "slug": "tri-clamp-power-piston",
     "why": "Ø8 shaft in the crank frame's 608s"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "crank-discs-5mm-bore",
     "why": "Ø5 bore, M3 grub on the flat"
    },
    {
     "slug": "nut-pocket-flywheels",
     "why": "Ø3 / Ø5 / Ø8 hub, M3 grub on the flat"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "shaft-spacers",
     "why": "set the 1 mm gaps along the shaft"
    },
    {
     "slug": "ball-bearings-metric",
     "why": "623 / 625 / 608"
    }
   ]
  }
 ],
 "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": "shafts, rods, pins",
   "exact": "Ø3 / Ø5 / Ø8",
   "mates": "the bores listed on each mating object",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "D-flat",
   "exact": "0.5 deep",
   "mates": "M3 grubs in hubs",
   "fit": "designed",
   "files": "crankshaft-"
  }
 ],
 "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": "What diameter crankshaft does a model Stirling engine need?",
   "a": "The bore of its bearings: Ø3 in 623s, Ø5 in 625s, Ø8 in 608s. The Ø5 and Ø8 files carry a 0.5 mm D-flat along their whole length."
  },
  {
   "q": "Why a D-flat?",
   "a": "So the M3 grub in each crank disc, web and flywheel hub bears on a flat and the hub cannot slip round the shaft."
  },
  {
   "q": "How is this different from the metric shafts page?",
   "a": "Those have a 20 mm motor-style flat 0.1 × d deep at one end; these have a 0.5 mm flat along the whole length so a hub can sit anywhere."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crankshaft-3x40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x40.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x40.stl",
   "note": "Ø3 × 40 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement"
  },
  {
   "file": "crankshaft-3x44",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x44.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x44.stl",
   "note": "Ø3 × 44 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement"
  },
  {
   "file": "crankshaft-3x60",
   "formats": [
    "step",
    "stl"
   ],
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x60.stl",
   "note": "Ø3 × 60 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement"
  },
  {
   "file": "crankshaft-3x80",
   "formats": [
    "step",
    "stl"
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-3x80.stl",
   "note": "Ø3 × 80 solid crankshaft for the crank head's 623 towers and the Ø3-bore crank discs; can engine skewer replacement"
  },
  {
   "file": "crankshaft-5x80-dflat",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x80-dflat.stl",
   "note": "Ø5 × 80 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5."
  },
  {
   "file": "crankshaft-5x100-dflat",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x100-dflat.stl",
   "note": "Ø5 × 100 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5."
  },
  {
   "file": "crankshaft-5x120-dflat",
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x120-dflat.stl",
   "note": "Ø5 × 120 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5."
  },
  {
   "file": "crankshaft-5x150-dflat",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-5x150-dflat.stl",
   "note": "Ø5 × 150 crankshaft with a full-length 0.5 mm D-flat (4.5 across) for the grubs; 625 crank stands, rhombic gears, crank discs, nut flywheel b5."
  },
  {
   "file": "crankshaft-8x80-dflat",
   "formats": [
    "step",
    "stl"
   ],
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   "license": "CC BY 4.0 (Xem Studio)",
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x80-dflat.stl",
   "note": "Ø8 × 80 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8."
  },
  {
   "file": "crankshaft-8x100-dflat",
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    "stl"
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x100-dflat.stl",
   "note": "Ø8 × 100 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8."
  },
  {
   "file": "crankshaft-8x120-dflat",
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    "stl"
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   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/crankshaft-8x120-dflat.stl",
   "note": "Ø8 × 120 crankshaft with a full-length 0.5 mm D-flat (7.5 across); tri-clamp crank frame 608s, crank webs, flywheels b8."
  }
 ],
 "markdown": "https://xemstudio.com/objects/stirling-crankshafts/index.md"
}