{
 "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": "hdd-platters",
 "name": "Hard-drive platters: 3.5 in Ø95 × 1.27 mm (Ø25 hole), 2.5 in Ø65 × 0.8 mm (Ø20 hole)",
 "kind": "standard",
 "category": "Hardware",
 "group": "Found & household materials",
 "year": null,
 "question": "What are hard drive platter dimensions?",
 "tags": [
  "hdd",
  "platter",
  "disc",
  "flywheel",
  "found materials",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "hard drive platter dimensions",
  "hdd platter hole size",
  "3.5 inch platter diameter",
  "2.5 inch platter size",
  "platter flywheel"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 2,
 "url": "https://xemstudio.com/objects/hdd-platters/",
 "sheet_txt": "https://xemstudio.com/objects/hdd-platters/sheet.txt",
 "sheet": {
  "basis": "3.5 in (95 mm) and 2.5 in (65 mm) hard-drive form-factor platters",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A 3.5 in drive platter is Ø95 × 1.27 mm (some 0.8–1.0) with a Ø25 mm centre hole, about 30 g.",
   "A 2.5 in drive platter is Ø65 × 0.8 mm with a Ø20 mm centre hole, about 7 g.",
   "Platters are flat and balanced; three 3.5 in platters stacked are about 90 g at Ø95.",
   "The hubs in the can-engine kit take a 3.5 in platter's Ø25 hole onto a 5 or 8 mm shaft (spigot drawn at Ø25.0)."
  ],
  "table": {
   "columns": [
    "platter",
    "dia_mm",
    "thickness_mm",
    "hole_mm",
    "mass_g"
   ],
   "rows": [
    [
     "3.5 in",
     95,
     1.27,
     25,
     30
    ],
    [
     "2.5 in",
     65,
     0.8,
     20,
     7
    ]
   ]
  }
 },
 "sheet_text": "Hard-drive platters: 3.5 in Ø95 × 1.27 mm (Ø25 hole), 2.5 in Ø65 × 0.8 mm (Ø20 hole) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/hdd-platters/  (CC BY 4.0)\nBasis: 3.5 in (95 mm) and 2.5 in (65 mm) hard-drive form-factor platters\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A 3.5 in drive platter is Ø95 × 1.27 mm (some 0.8–1.0) with a Ø25 mm centre hole, about 30 g.\n- A 2.5 in drive platter is Ø65 × 0.8 mm with a Ø20 mm centre hole, about 7 g.\n- Platters are flat and balanced; three 3.5 in platters stacked are about 90 g at Ø95.\n- The hubs in the can-engine kit take a 3.5 in platter's Ø25 hole onto a 5 or 8 mm shaft (spigot drawn at Ø25.0).\n\nplatter  dia_mm  thickness_mm  hole_mm  mass_g\n3.5 in  95  1.27  25  30\n2.5 in  65  0.8  20  7\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Compact disc — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Compact_disc\n- Wikipedia: Hard disk drive platter — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Hard_disk_drive_platter\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, 2 parts): https://xemstudio.com/files/hardware/hdd-platters/index.json\nAPI: https://xemstudio.com/api/geometry?object=hdd-platters\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Compact disc",
   "url": "https://en.wikipedia.org/wiki/Compact_disc",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Hard disk drive platter",
   "url": "https://en.wikipedia.org/wiki/Hard_disk_drive_platter",
   "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
  }
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 "xem": {
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  "sheet_free": true,
  "mesh_price_usd": null,
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  "tolerance_mm": null
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 "related": [
  "cd-dvd-discs",
  "can-engine-cap",
  "crank-discs-5mm-bore",
  "2-5-inch-drive"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "can-engine-cap",
     "why": "Ø25 hole on the hub's Ø25.0 spigot"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "cd-dvd-discs",
     "why": "lighter Ø120 disc"
    },
    {
     "slug": "crank-discs-5mm-bore",
     "why": "a drawn flywheel"
    }
   ]
  }
 ],
 "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 are 3.5 inch hard drive platter dimensions?",
   "a": "Ø95 mm, Ø25 mm hole, about 1.27 mm thick (0.8–1.0 in some drives)."
  },
  {
   "q": "What is a 2.5 inch platter's size?",
   "a": "Ø65 × 0.8 mm with a Ø20 mm hole."
  },
  {
   "q": "Are all 3.5 in platters the same thickness?",
   "a": "No; 1.27 mm is common, some drives use 0.8–1.0 mm platters with the same Ø95 / Ø25 size."
  }
 ],
 "files_license": null,
 "offers": [
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   "file": "hdd-platter-3-5in",
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   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-3-5in.step",
   "stl": "https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-3-5in.stl",
   "note": "3.5 in hard-drive platter: Ø95 × 1.27, Ø25 hole (aluminium or glass)"
  },
  {
   "file": "hdd-platter-2-5in",
   "formats": [
    "step",
    "stl"
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   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-2-5in.step",
   "stl": "https://xemstudio.com/files/hardware/cd-dvd-and-drive-platters/hdd-platter-2-5in.stl",
   "note": "2.5 in platter: Ø65 × 0.8, Ø20 hole"
  }
 ],
 "markdown": "https://xemstudio.com/objects/hdd-platters/index.md"
}