{
 "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": "ping-pong-ball",
 "name": "Ping-pong ball Ø40 mm, 0.4 mm wall",
 "kind": "standard",
 "category": "Hardware",
 "group": "Found & household materials",
 "year": null,
 "question": "What size is a ping-pong ball?",
 "tags": [
  "ping pong",
  "table tennis",
  "ball",
  "displacer",
  "found materials",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "ping pong ball size",
  "table tennis ball diameter",
  "40mm ball",
  "ping pong ball wall thickness",
  "ping pong ball displacer"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/ping-pong-ball/",
 "sheet_txt": "https://xemstudio.com/objects/ping-pong-ball/sheet.txt",
 "sheet": {
  "basis": "ITTF table-tennis ball: Ø40.0, 2.7 g; drawn as a hollow sphere with a 0.4 mm wall",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A table-tennis ball is Ø40.0 mm and weighs 2.7 g (ITTF).",
   "The file is a hollow sphere: Ø40.0 outside, 0.4 mm wall (Ø39.2 inside).",
   "At 2.7 g it is the lightest ready-made hollow sphere of that size, which makes it useful as a displacer in small demonstrator engines."
  ],
  "table": {
   "columns": [
    "ball",
    "od_mm",
    "wall_mm",
    "mass_g"
   ],
   "rows": [
    [
     "table-tennis ball",
     40,
     0.4,
     2.7
    ]
   ]
  }
 },
 "sheet_text": "Ping-pong ball Ø40 mm, 0.4 mm wall — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/ping-pong-ball/  (CC BY 4.0)\nBasis: ITTF table-tennis ball: Ø40.0, 2.7 g; drawn as a hollow sphere with a 0.4 mm wall\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A table-tennis ball is Ø40.0 mm and weighs 2.7 g (ITTF).\n- The file is a hollow sphere: Ø40.0 outside, 0.4 mm wall (Ø39.2 inside).\n- At 2.7 g it is the lightest ready-made hollow sphere of that size, which makes it useful as a displacer in small demonstrator engines.\n\nball  od_mm  wall_mm  mass_g\ntable-tennis ball  40.0  0.4  2.7\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Craft stick — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Craft_stick\n- Wikipedia: BB gun — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/BB_gun\n- Wikipedia: Table tennis — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Table_tennis\n- Long Earth Society: Engine builds (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/ping-pong-ball/index.json\nAPI: https://xemstudio.com/api/geometry?object=ping-pong-ball\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Craft stick",
   "url": "https://en.wikipedia.org/wiki/Craft_stick",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "BB gun",
   "url": "https://en.wikipedia.org/wiki/BB_gun",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Table tennis",
   "url": "https://en.wikipedia.org/wiki/Table_tennis",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds (videos and write-ups)",
   "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": [
  "glass-marbles",
  "steel-and-airsoft-bbs",
  "borosilicate-test-tubes",
  "can-engine-cap"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "can-engine-cap",
     "why": "lightweight displacer in a small demonstrator"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "glass-marbles",
     "why": "a solid Ø16 ball"
    }
   ]
  }
 ],
 "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 is the diameter of a ping-pong ball?",
   "a": "40.0 mm (ITTF), weighing 2.7 g."
  },
  {
   "q": "How thick is a ping-pong ball wall?",
   "a": "About 0.4 mm; the file is drawn with a 0.4 mm wall, Ø39.2 inside."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "ping-pong-ball-40mm",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/sticks-skewers-wire-bbs/ping-pong-ball-40mm.step",
   "stl": "https://xemstudio.com/files/hardware/sticks-skewers-wire-bbs/ping-pong-ball-40mm.stl",
   "note": "table-tennis ball Ø40.0, 0.4 mm wall, 2.7 g"
  }
 ],
 "markdown": "https://xemstudio.com/objects/ping-pong-ball/index.md"
}