{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "gt3-timing-pulleys-3mm-pitch",
 "name": "GT3 (3GT, 3 mm pitch) timing pulleys: pitch diameter and outside diameter, 16T to 80T",
 "kind": "standard",
 "category": "Hardware",
 "group": "Bearings, rails & motion",
 "year": null,
 "question": "What is the pitch diameter and outside diameter of a GT3 (3GT, 3 mm pitch) timing pulley with N teeth?",
 "tags": [
  "gt3",
  "3gt",
  "3mm pitch",
  "timing pulley",
  "pulley",
  "belt",
  "motion",
  "tool"
 ],
 "aliases": [
  "gt3 pulley dimensions",
  "3gt pulley outside diameter",
  "gt3 pulley 20 tooth",
  "gt2-3m pulley",
  "3gt pulley 20t diameter",
  "3mm pitch pulley pitch diameter",
  "gt3 vs gt2",
  "gt3 pulley od formula"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/gt3-timing-pulleys-3mm-pitch/",
 "sheet_txt": "https://xemstudio.com/objects/gt3-timing-pulleys-3mm-pitch/sheet.txt",
 "sheet": {
  "basis": "PD = 3 N / pi; OD = PD − 0.762 mm, checked on two 20-tooth pulleys (KSC Direct / SDP, RatRig); other rows are the rule, not a maker table",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "GT3 / 3GT (3 mm pitch, also sold as GT2-3M): PD = teeth x 3 / pi. OD = PD − 0.762 mm, i.e. a pitch-line differential of 0.381 mm. That rule rests on two 20-tooth pulleys from two sellers: SDP/SI part 20-3P06M6FA6 via KSC prints PD 19.1 / OD 18.3 (flange Ø22.7, 6 mm belt, 6 mm bore) and RatRig's 9 mm pulley prints PD 0.752 in / OD 0.722 in (19.10 / 18.34 mm; hub 0.5 in, overall width 0.813 in, 1/4 in bore). No GT3 table of other tooth counts was readable, so the other rows apply the rule and are not maker values.",
   "Belt moves 3 mm per tooth: a 20T pulley moves 60 mm per turn (on a 200-step motor at 16x microstepping that is 3200 / 60 = 53.3 microsteps per mm).",
   "Sellers list 3 mm pulleys as 'for GT2 or GT3 belts' (KSC) and as 3GT / GT2-3M (RatRig); check the profile printed on the pulley you buy.",
   "No files: the GT3 tooth form is not published in any source read, and a made-up groove would not mesh."
  ],
  "table": {
   "columns": [
    "teeth",
    "pitch Ø PD, mm",
    "outside Ø OD (PD − 0.762), mm",
    "belt travel per turn, mm"
   ],
   "rows": [
    [
     16,
     "15.28",
     "14.52",
     "48"
    ],
    [
     18,
     "17.19",
     "16.43",
     "54"
    ],
    [
     20,
     "19.10",
     "18.34",
     "60"
    ],
    [
     22,
     "21.01",
     "20.25",
     "66"
    ],
    [
     24,
     "22.92",
     "22.16",
     "72"
    ],
    [
     28,
     "26.74",
     "25.98",
     "84"
    ],
    [
     30,
     "28.65",
     "27.89",
     "90"
    ],
    [
     32,
     "30.56",
     "29.80",
     "96"
    ],
    [
     36,
     "34.38",
     "33.62",
     "108"
    ],
    [
     40,
     "38.20",
     "37.44",
     "120"
    ],
    [
     44,
     "42.02",
     "41.25",
     "132"
    ],
    [
     48,
     "45.84",
     "45.07",
     "144"
    ],
    [
     60,
     "57.30",
     "56.53",
     "180"
    ],
    [
     72,
     "68.75",
     "67.99",
     "216"
    ],
    [
     80,
     "76.39",
     "75.63",
     "240"
    ]
   ]
  }
 },
 "sheet_text": "GT3 (3GT, 3 mm pitch) timing pulleys: pitch diameter and outside diameter, 16T to 80T — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/gt3-timing-pulleys-3mm-pitch/  (sheet CC BY 4.0)\nBasis: PD = 3 N / pi; OD = PD − 0.762 mm, checked on two 20-tooth pulleys (KSC Direct / SDP, RatRig); other rows are the rule, not a maker table\nCatalog version: 2026-10-20\n\nSizes: see table below\n- GT3 / 3GT (3 mm pitch, also sold as GT2-3M): PD = teeth x 3 / pi. OD = PD − 0.762 mm, i.e. a pitch-line differential of 0.381 mm. That rule rests on two 20-tooth pulleys from two sellers: SDP/SI part 20-3P06M6FA6 via KSC prints PD 19.1 / OD 18.3 (flange Ø22.7, 6 mm belt, 6 mm bore) and RatRig's 9 mm pulley prints PD 0.752 in / OD 0.722 in (19.10 / 18.34 mm; hub 0.5 in, overall width 0.813 in, 1/4 in bore). No GT3 table of other tooth counts was readable, so the other rows apply the rule and are not maker values.\n- Belt moves 3 mm per tooth: a 20T pulley moves 60 mm per turn (on a 200-step motor at 16x microstepping that is 3200 / 60 = 53.3 microsteps per mm).\n- Sellers list 3 mm pulleys as 'for GT2 or GT3 belts' (KSC) and as 3GT / GT2-3M (RatRig); check the profile printed on the pulley you buy.\n- No files: the GT3 tooth form is not published in any source read, and a made-up groove would not mesh.\n\nteeth  pitch Ø PD, mm  outside Ø OD (PD − 0.762), mm  belt travel per turn, mm\n16  15.28  14.52  48\n18  17.19  16.43  54\n20  19.10  18.34  60\n22  21.01  20.25  66\n24  22.92  22.16  72\n28  26.74  25.98  84\n30  28.65  27.89  90\n32  30.56  29.80  96\n36  34.38  33.62  108\n40  38.20  37.44  120\n44  42.02  41.25  132\n48  45.84  45.07  144\n60  57.30  56.53  180\n72  68.75  67.99  216\n80  76.39  75.63  240\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- KSC Direct (SDP/SI part 20-3P06M6FA6): 3 mm pitch 20-tooth timing pulley, 6 mm belt, 6 mm bore: PD 19.1, OD 18.3, flange 22.7 — web — Publisher's page; dimensions are facts — https://kscdirect.com/itemDetail/7281045/20-3p06m6fa6-timing-pulley-aluminum-clear-anodized\n- RatRig: 3GT (GT2-3M) 20-tooth pulley, 9 mm belt, 1/4 in bore: PD 0.752 in, OD 0.722 in, hub 0.5 in, overall 0.813 in — web — Publisher's page; dimensions are facts — https://ratrig.com/products/timing-pulley-3gt-gt2-3m-20-tooth-9mm-belt-25-bore\n- Pfeifer Industries: Timing belt pulley PD / OD charts: PD = pitch x teeth / pi, OD = PD - 2 U (U = cord to tooth root) — web — Publisher's page; dimensions are facts — https://www.pfeiferindustries.com/information.php?info_id=12\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=gt3-timing-pulleys-3mm-pitch\n",
 "sources": [
  {
   "publisher": "KSC Direct (SDP/SI part 20-3P06M6FA6)",
   "title": "3 mm pitch 20-tooth timing pulley, 6 mm belt, 6 mm bore: PD 19.1, OD 18.3, flange 22.7",
   "url": "https://kscdirect.com/itemDetail/7281045/20-3p06m6fa6-timing-pulley-aluminum-clear-anodized",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "RatRig",
   "title": "3GT (GT2-3M) 20-tooth pulley, 9 mm belt, 1/4 in bore: PD 0.752 in, OD 0.722 in, hub 0.5 in, overall 0.813 in",
   "url": "https://ratrig.com/products/timing-pulley-3gt-gt2-3m-20-tooth-9mm-belt-25-bore",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Pfeifer Industries",
   "title": "Timing belt pulley PD / OD charts: PD = pitch x teeth / pi, OD = PD - 2 U (U = cord to tooth root)",
   "url": "https://www.pfeiferindustries.com/information.php?info_id=12",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "gt2-timing-pulleys-18-60t-bores",
  "gt2-pulleys",
  "timing-belt-profiles-pitch-and-tooth",
  "htd-3m-5m-belt-lengths"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no tolerance added)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no tolerance added. 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. Typical accuracy by process and ISO 286 fits: https://xemstudio.com/tolerances/",
 "mating": [],
 "faq": [
  {
   "q": "What is the outside diameter of a 20 tooth GT3 pulley?",
   "a": "18.34 mm: pitch diameter 19.10 mm minus 0.762 mm."
  },
  {
   "q": "How far does a GT3 belt move per tooth?",
   "a": "3 mm; a 20T pulley moves the belt 60 mm per revolution."
  },
  {
   "q": "Is GT3 the same as 3GT?",
   "a": "Sellers use 3GT, GT3 and GT2-3M for the same 3 mm profile; the numbers above are for it."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/gt3-timing-pulleys-3mm-pitch/index.md"
}