{
 "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": "pins-3mm",
 "name": "Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What size pin is a crank pin, wrist pin or link pivot on a small engine?",
 "tags": [
  "pin",
  "crank pin",
  "wrist pin",
  "3 mm",
  "pivot",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "3mm crank pin",
  "3mm wrist pin",
  "3mm pin step",
  "crank pin size model engine"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 5,
 "url": "https://xemstudio.com/objects/pins-3mm/",
 "sheet_txt": "https://xemstudio.com/objects/pins-3mm/sheet.txt",
 "sheet": {
  "basis": "Solid Ø3 pins at the Ø3 pin holes of the crank discs, webs, clevises and pistons",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Solid Ø3 pins, 12, 16, 19, 20 and 23 long, 0.3 chamfers both ends.",
   "They sit fixed in the crank disc and web pin holes, the yoke and the clevis tines, and the con-rods turn on them; each fit is listed under Mating features.",
   "Ø3 × 16 is the wrist pin through the free-piston plug legs; Ø3 × 23 is the alpha V-twin crank pin (disc 6, two rods and two 1 mm spacers, then a full 5 mm collar) and the Ross yoke's rocking pin."
  ],
  "table": {
   "columns": [
    "file",
    "Ø",
    "length"
   ],
   "rows": [
    [
     "pin-3x12",
     3,
     12
    ],
    [
     "pin-3x16",
     3,
     16
    ],
    [
     "pin-3x19",
     3,
     19
    ],
    [
     "pin-3x20",
     3,
     20
    ],
    [
     "pin-3x23",
     3,
     23
    ]
   ]
  }
 },
 "sheet_text": "Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/pins-3mm/  (CC BY 4.0)\nBasis: Solid Ø3 pins at the Ø3 pin holes of the crank discs, webs, clevises and pistons\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Solid Ø3 pins, 12, 16, 19, 20 and 23 long, 0.3 chamfers both ends.\n- They sit fixed in the crank disc and web pin holes, the yoke and the clevis tines, and the con-rods turn on them; each fit is listed under Mating features.\n- Ø3 × 16 is the wrist pin through the free-piston plug legs; Ø3 × 23 is the alpha V-twin crank pin (disc 6, two rods and two 1 mm spacers, then a full 5 mm collar) and the Ross yoke's rocking pin.\n\nfile  Ø  length\npin-3x12  3  12\npin-3x16  3  16\npin-3x19  3  19\npin-3x20  3  20\npin-3x23  3  23\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, 5 parts): https://xemstudio.com/files/hardware/pins-3mm/index.json\nAPI: https://xemstudio.com/api/geometry?object=pins-3mm\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": [
  "dowel-pins-metric",
  "crank-discs-5mm-bore",
  "connecting-rods-623",
  "rod-clevises",
  "clevis-pins"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "crank-discs-5mm-bore",
     "why": "Ø3 pin hole at stroke / 2"
    },
    {
     "slug": "rod-clevises",
     "why": "Ø3 hole across the 5 mm gap"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "connecting-rods-623",
     "why": "623 bore on the pin"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "dowel-pins-metric",
     "why": "ISO 2338 Ø3 dowel"
    }
   ]
  }
 ],
 "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"
  }
 ],
 "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 crank pin fits a 623 bearing?",
   "a": "Ø3, the 623 bore. The pins are 12, 16, 19, 20 and 23 long."
  },
  {
   "q": "Which pin is the wrist pin?",
   "a": "Ø3 × 16 through the piston plug legs."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "pin-3x12",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x12.stl",
   "note": "Ø3 × 12 pin: crank pin, wrist pin, link pivot"
  },
  {
   "file": "pin-3x16",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x16.stl",
   "note": "Ø3 × 16 pin: crank pin, wrist pin, link pivot"
  },
  {
   "file": "pin-3x19",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x19.stl",
   "note": "Ø3 × 19 pin: crank pin, wrist pin, link pivot"
  },
  {
   "file": "pin-3x20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x20.stl",
   "note": "Ø3 × 20 pin: crank pin, wrist pin, link pivot"
  },
  {
   "file": "pin-3x23",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x23.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-shafts-and-rods/pin-3x23.stl",
   "note": "Ø3 × 23 pin: crank pin, wrist pin, link pivot"
  }
 ],
 "markdown": "https://xemstudio.com/objects/pins-3mm/index.md"
}