{
 "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": "crank-discs-3mm-bore",
 "name": "Crank discs Ø30 for a Ø3 crankshaft, 10 to 20 mm stroke",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What crank disc fits a 3 mm crankshaft?",
 "tags": [
  "crank disc",
  "crank",
  "3 mm shaft",
  "stroke",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "crank disc 3mm bore",
  "3mm shaft crank",
  "can engine crank disc",
  "crank head crank disc"
 ],
 "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/crank-discs-3mm-bore/",
 "sheet_txt": "https://xemstudio.com/objects/crank-discs-3mm-bore/sheet.txt",
 "sheet": {
  "basis": "Ø30 × 6 disc, Ø3 bore, Ø3 pin hole at stroke / 2, M3 grub",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A Ø30 × 6 disc with a Ø3 bore for the crank head's Ø3 crankshaft (623 towers) or the can engine's Ø3 shaft.",
   "A Ø3 pin hole at 5.0, 7.5 or 10.0 mm from the axis gives 10, 15 or 20 mm stroke.",
   "A radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft."
  ],
  "table": {
   "columns": [
    "file",
    "stroke",
    "pin offset",
    "disc",
    "bore"
   ],
   "rows": [
    [
     "crank-disc-b3-stroke10",
     10,
     5,
     "Ø30 × 6",
     3
    ],
    [
     "crank-disc-b3-stroke15",
     15,
     7.5,
     "Ø30 × 6",
     3
    ],
    [
     "crank-disc-b3-stroke20",
     20,
     10,
     "Ø30 × 6",
     3
    ]
   ]
  }
 },
 "sheet_text": "Crank discs Ø30 for a Ø3 crankshaft, 10 to 20 mm stroke — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/crank-discs-3mm-bore/  (CC BY 4.0)\nBasis: Ø30 × 6 disc, Ø3 bore, Ø3 pin hole at stroke / 2, M3 grub\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A Ø30 × 6 disc with a Ø3 bore for the crank head's Ø3 crankshaft (623 towers) or the can engine's Ø3 shaft.\n- A Ø3 pin hole at 5.0, 7.5 or 10.0 mm from the axis gives 10, 15 or 20 mm stroke.\n- A radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft.\n\nfile  stroke  pin offset  disc  bore\ncrank-disc-b3-stroke10  10  5.0  Ø30 × 6  3\ncrank-disc-b3-stroke15  15  7.5  Ø30 × 6  3\ncrank-disc-b3-stroke20  20  10.0  Ø30 × 6  3\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Tri-clamp Stirling engine builds — 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/crank-discs-3mm-bore/index.json\nAPI: https://xemstudio.com/api/geometry?object=crank-discs-3mm-bore\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Tri-clamp Stirling 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": [
  "crank-discs-5mm-bore",
  "stirling-crankshafts",
  "connecting-rods-623",
  "pins-3mm",
  "tri-clamp-displacer"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "stirling-crankshafts",
     "why": "Ø3 crankshaft in the bore"
    },
    {
     "slug": "tri-clamp-displacer",
     "why": "on the crank head's Ø3 shaft between the 623 towers"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "connecting-rods-623",
     "why": "623 end on the Ø3 pin"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "crank-discs-5mm-bore",
     "why": "same discs for a Ø5 shaft"
    }
   ]
  }
 ],
 "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": "crank-disc bore",
   "exact": "Ø3",
   "mates": "Ø3 crankshaft (M3 grub)",
   "fit": "slide",
   "files": "crank-disc-b3-"
  },
  {
   "feature": "crank-disc pin hole",
   "exact": "Ø3",
   "mates": "Ø3 crank pin",
   "fit": "press",
   "files": "crank-disc-b3-"
  },
  {
   "feature": "crank-disc grub hole",
   "exact": "Ø2.5",
   "mates": "M3 tap drill",
   "fit": "designed",
   "files": "crank-disc-b3-"
  }
 ],
 "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 crank disc fits a 3 mm shaft?",
   "a": "Crank-disc-b3: Ø30 × 6, Ø3 bore, M3 grub, pin at 5, 7.5 or 10 mm."
  },
  {
   "q": "How is the stroke set?",
   "a": "Stroke = 2 × pin offset: 10, 15 or 20 mm."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-disc-b3-stroke10",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 5.0 mm (10 mm stroke), M3 grub"
  },
  {
   "file": "crank-disc-b3-stroke15",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 7.5 mm (15 mm stroke), M3 grub"
  },
  {
   "file": "crank-disc-b3-stroke20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 10.0 mm (20 mm stroke), M3 grub"
  }
 ],
 "markdown": "https://xemstudio.com/objects/crank-discs-3mm-bore/index.md"
}