{
 "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": "inch-ball-bearings-r-series-r188-r144-r166",
 "name": "Inch ball bearings R-series: R188, R144, R166, R2, R3, R4, R6 to R24: bore, OD, width, r + 22 ring-envelope STEP/STL files (1/8 to 1-1/2 in bore)",
 "kind": "standard",
 "category": "Hardware",
 "group": "Bearings, rails & motion",
 "year": null,
 "question": "What are the dimensions of an R188, R144, R166, R2, R3, R4, R6 or R8 inch ball bearing: bore, OD and width, with and without shields?",
 "tags": [
  "inch ball bearing",
  "r188",
  "r144",
  "r166",
  "r188zz",
  "fidget spinner bearing",
  "miniature bearing",
  "r4",
  "r6",
  "r8",
  "r series bearing"
 ],
 "aliases": [
  "R188 bearing dimensions",
  "R188ZZ dimensions",
  "R188 6.35x12.7x3.175",
  "R188 1/4 x 1/2 x 1/8",
  "R144 dimensions",
  "R166 dimensions",
  "R2 bearing dimensions",
  "R3 bearing dimensions",
  "R4 bearing dimensions",
  "R6 bearing dimensions",
  "R8 bearing dimensions",
  "R10 bearing dimensions",
  "R12 bearing dimensions",
  "1/4 x 1/2 bearing",
  "1/4 x 5/8 bearing",
  "1/8 x 3/8 bearing",
  "3/8 x 7/8 bearing",
  "3/16 x 3/8 bearing",
  "fidget spinner bearing size R188",
  "inch miniature bearing stl",
  "R188 bearing step file",
  "R188ZZ vs R188 width",
  "R4ZZ dimensions"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 22,
 "url": "https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/",
 "sheet_txt": "https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/sheet.txt",
 "sheet": {
  "basis": "NSK inch-series table (r min), NSK R166 / R188ZZ pages, Emerson Bearing R2 to R24 list, checked against TFL Bearing's SKF-designation table; maker pages linked",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "R-series ball bearings are the inch-size miniature and small deep-groove bearings: R2 is 1/8 in bore, R4 is 1/4 in bore, R6 is 3/8 in, R8 is 1/2 in. R144, R166 and R188 are the thin-section sizes (1/8 x 1/4, 3/16 x 3/8 and 1/4 x 1/2 in bore x OD). R188 (6.35 x 12.7 x 3.175 open, 4.762 with shields) is a popular size for fidget spinners, small pulleys and RC parts.",
   "Numbers: NSK's inch-series table (R09 to R2A, the first 20 of 41 items, with r min), NSK's R166 and R188ZZ pages, Emerson Bearing's R2 to R24 list in inches (the mm there are the printed inch decimals times 25.4, and they reproduce the SKF and NSK mm values to 0.001 on every shared row), and TFL Bearing's table of the SKF catalogue designations (R1-4 to R6, WR) used as the independent mm check: NSK and TFL agree on every shared row except that NSK prints 4.762 and TFL 4.763 for 3/16 in (4.7625 mm); NSK's value is used. Two Emerson entries disagree with the other sources and are not used: its R3 bore is printed 0.1880 in (3/16 in is 0.1875; TFL / SKF 4.763 mm is shown) and its R4A OD is printed 0.6250 in, the R4 size (TFL / SKF has 19.050 mm, 3/4 in, which is shown; the R4A widths 0.2188 and 0.2812 in agree).",
   "R188: the open bearing is 6.35 x 12.7 x 3.175 mm (TFL, SKDIN: 0.25 x 0.5 x 0.125 in), the ZZ / 2Z / 2RS is 4.762 mm wide (NSK R188ZZ; TFL R188-2Z prints 4.763; MBA R188AZZMC3 4.762). r min 0.15 is NSK's value for the R188ZZ; NSK's R188 open page could not be read, so the open bearing has no printed r here and no file.",
   "Files: 22 ring envelopes for every row that NSK prints with r min (R09 to R2A, R166, R188ZZ): one solid ring, bore, OD, width and corners rounded at r min. No balls, retainer or shield. R3 to R24 and the SKF-only rows have no r read, so they are tables only.",
   "Left out: the other 21 NSK rows (not readable), R4A and larger r min, flanged inch bearings (FR series), thin-section 'RW' sizes, light-duty 1600 series (own page), load ratings, limiting speeds, metric miniature bearings (see the 600/MR series pages)."
  ],
  "table": {
   "columns": [
    "designation",
    "bore d, mm",
    "OD D, mm",
    "width B open, mm",
    "width B ZZ / 2RS / 2Z, mm",
    "bore x OD (inch, as printed)",
    "r min, mm",
    "source"
   ],
   "rows": [
    [
     "R09",
     "1.016",
     "3.175",
     "1.191",
     "—",
     "—",
     "0.1",
     "NSK"
    ],
    [
     "R0",
     "1.191",
     "3.967",
     "1.588",
     "2.38",
     "—",
     "0.1",
     "NSK"
    ],
    [
     "R1",
     "1.397",
     "4.762",
     "1.984",
     "2.779",
     "—",
     "0.1",
     "NSK"
    ],
    [
     "R1-4",
     "1.984",
     "6.35",
     "2.38",
     "3.571",
     "5/64 x 1/4",
     "0.1",
     "NSK; TFL (SKF)"
    ],
    [
     "R133",
     "2.38",
     "4.762",
     "1.588",
     "2.38",
     "3/32 x 3/16",
     "0.1",
     "NSK; TFL (SKF)"
    ],
    [
     "R1-5",
     "2.38",
     "7.938",
     "2.779",
     "3.571",
     "3/32 x 5/16",
     "0.15",
     "NSK; TFL (SKF)"
    ],
    [
     "R144",
     "3.175",
     "6.35",
     "2.38",
     "2.779",
     "1/8 x 1/4",
     "0.1",
     "NSK; TFL (SKF)"
    ],
    [
     "R2-5",
     "3.175",
     "7.938",
     "2.779",
     "3.571",
     "1/8 x 5/16",
     "0.1",
     "NSK; TFL (SKF)"
    ],
    [
     "R2-6",
     "3.175",
     "9.525",
     "2.779",
     "3.571",
     "1/8 x 3/8",
     "0.15",
     "NSK; TFL (SKF)"
    ],
    [
     "R2",
     "3.175",
     "9.525",
     "3.967",
     "3.967",
     "1/8 x 3/8",
     "0.3",
     "NSK; TFL (SKF); Emerson"
    ],
    [
     "R2A",
     "3.175",
     "12.7",
     "4.366",
     "4.366",
     "1/8 x 1/2",
     "0.3",
     "NSK; TFL (SKF); Emerson"
    ],
    [
     "R166",
     "4.762",
     "9.525",
     "3.175",
     "3.175",
     "3/16 x 3/8",
     "0.1",
     "NSK; TFL (SKF)"
    ],
    [
     "R188",
     "6.35",
     "12.7",
     "3.175",
     "4.762",
     "1/4 x 1/2",
     "0.15 (R188ZZ)",
     "NSK; TFL (SKF); SKDIN, MBA"
    ],
    [
     "R155",
     "3.967",
     "7.938",
     "2.779",
     "3.175",
     "5/32 x 5/16",
     "—",
     "TFL (SKF)"
    ],
    [
     "R156",
     "4.763",
     "7.938",
     "2.779",
     "3.175",
     "3/16 x 5/16",
     "—",
     "TFL (SKF)"
    ],
    [
     "R3",
     "4.763",
     "12.7",
     "3.967",
     "4.978",
     "3/16 x 1/2",
     "—",
     "TFL (SKF); Emerson"
    ],
    [
     "R3A",
     "4.763",
     "15.875",
     "4.978",
     "4.978",
     "3/16 x 5/8",
     "—",
     "TFL (SKF)"
    ],
    [
     "R168",
     "6.35",
     "9.525",
     "3.175",
     "3.175",
     "1/4 x 3/8",
     "—",
     "TFL (SKF)"
    ],
    [
     "R4",
     "6.35",
     "15.875",
     "4.978",
     "4.978",
     "1/4 x 5/8",
     "—",
     "TFL (SKF); Emerson"
    ],
    [
     "R4A",
     "6.35",
     "19.05",
     "5.558",
     "7.142",
     "1/4 x 3/4",
     "—",
     "TFL (SKF); Emerson"
    ],
    [
     "R6",
     "9.525",
     "22.225",
     "5.558",
     "7.142",
     "3/8 x 7/8",
     "—",
     "TFL (SKF); Emerson"
    ],
    [
     "R8",
     "12.7",
     "28.575",
     "6.35",
     "7.938",
     "0.5000 x 1.1250 x 0.2500 / 0.3125",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R10",
     "15.875",
     "34.925",
     "7.142",
     "8.733",
     "0.6250 x 1.375 x 0.2812 / 0.3438",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R12",
     "19.05",
     "41.275",
     "7.938",
     "11.113",
     "0.7500 x 1.625 x 0.3125 / 0.4375",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R14",
     "22.225",
     "47.625",
     "9.525",
     "12.7",
     "0.8750 x 1.875 x 0.3750 / 0.5000",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R16",
     "25.4",
     "50.8",
     "9.525",
     "12.7",
     "1.0000 x 2.0000 x 0.3750 / 0.5000",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R18",
     "28.575",
     "53.975",
     "9.525",
     "12.7",
     "1.1250 x 2.125 x 0.3750 / 0.5000",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R20",
     "31.75",
     "57.15",
     "9.525",
     "12.7",
     "1.2500 x 2.250 x 0.3750 / 0.5000",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R22",
     "34.925",
     "63.5",
     "11.113",
     "14.288",
     "1.3750 x 2.5000 x 0.4375 / 0.5625",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ],
    [
     "R24",
     "38.1",
     "66.675",
     "11.113",
     "14.288",
     "1.5000 x 2.6250 x 0.4375 / 0.5625",
     "—",
     "Emerson (mm = printed inch x 25.4)"
    ]
   ]
  }
 },
 "sheet_text": "Inch ball bearings R-series: R188, R144, R166, R2, R3, R4, R6 to R24: bore, OD, width, r + 22 ring-envelope STEP/STL files (1/8 to 1-1/2 in bore) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/  (sheet CC BY 4.0)\nBasis: NSK inch-series table (r min), NSK R166 / R188ZZ pages, Emerson Bearing R2 to R24 list, checked against TFL Bearing's SKF-designation table; maker pages linked\nCatalog version: 2026-10-20\n\nSizes: see table below\n- R-series ball bearings are the inch-size miniature and small deep-groove bearings: R2 is 1/8 in bore, R4 is 1/4 in bore, R6 is 3/8 in, R8 is 1/2 in. R144, R166 and R188 are the thin-section sizes (1/8 x 1/4, 3/16 x 3/8 and 1/4 x 1/2 in bore x OD). R188 (6.35 x 12.7 x 3.175 open, 4.762 with shields) is a popular size for fidget spinners, small pulleys and RC parts.\n- Numbers: NSK's inch-series table (R09 to R2A, the first 20 of 41 items, with r min), NSK's R166 and R188ZZ pages, Emerson Bearing's R2 to R24 list in inches (the mm there are the printed inch decimals times 25.4, and they reproduce the SKF and NSK mm values to 0.001 on every shared row), and TFL Bearing's table of the SKF catalogue designations (R1-4 to R6, WR) used as the independent mm check: NSK and TFL agree on every shared row except that NSK prints 4.762 and TFL 4.763 for 3/16 in (4.7625 mm); NSK's value is used. Two Emerson entries disagree with the other sources and are not used: its R3 bore is printed 0.1880 in (3/16 in is 0.1875; TFL / SKF 4.763 mm is shown) and its R4A OD is printed 0.6250 in, the R4 size (TFL / SKF has 19.050 mm, 3/4 in, which is shown; the R4A widths 0.2188 and 0.2812 in agree).\n- R188: the open bearing is 6.35 x 12.7 x 3.175 mm (TFL, SKDIN: 0.25 x 0.5 x 0.125 in), the ZZ / 2Z / 2RS is 4.762 mm wide (NSK R188ZZ; TFL R188-2Z prints 4.763; MBA R188AZZMC3 4.762). r min 0.15 is NSK's value for the R188ZZ; NSK's R188 open page could not be read, so the open bearing has no printed r here and no file.\n- Files: 22 ring envelopes for every row that NSK prints with r min (R09 to R2A, R166, R188ZZ): one solid ring, bore, OD, width and corners rounded at r min. No balls, retainer or shield. R3 to R24 and the SKF-only rows have no r read, so they are tables only.\n- Left out: the other 21 NSK rows (not readable), R4A and larger r min, flanged inch bearings (FR series), thin-section 'RW' sizes, light-duty 1600 series (own page), load ratings, limiting speeds, metric miniature bearings (see the 600/MR series pages).\n\ndesignation  bore d, mm  OD D, mm  width B open, mm  width B ZZ / 2RS / 2Z, mm  bore x OD (inch, as printed)  r min, mm  source\nR09  1.016  3.175  1.191  —  —  0.1  NSK\nR0  1.191  3.967  1.588  2.38  —  0.1  NSK\nR1  1.397  4.762  1.984  2.779  —  0.1  NSK\nR1-4  1.984  6.35  2.38  3.571  5/64 x 1/4  0.1  NSK; TFL (SKF)\nR133  2.38  4.762  1.588  2.38  3/32 x 3/16  0.1  NSK; TFL (SKF)\nR1-5  2.38  7.938  2.779  3.571  3/32 x 5/16  0.15  NSK; TFL (SKF)\nR144  3.175  6.35  2.38  2.779  1/8 x 1/4  0.1  NSK; TFL (SKF)\nR2-5  3.175  7.938  2.779  3.571  1/8 x 5/16  0.1  NSK; TFL (SKF)\nR2-6  3.175  9.525  2.779  3.571  1/8 x 3/8  0.15  NSK; TFL (SKF)\nR2  3.175  9.525  3.967  3.967  1/8 x 3/8  0.3  NSK; TFL (SKF); Emerson\nR2A  3.175  12.7  4.366  4.366  1/8 x 1/2  0.3  NSK; TFL (SKF); Emerson\nR166  4.762  9.525  3.175  3.175  3/16 x 3/8  0.1  NSK; TFL (SKF)\nR188  6.35  12.7  3.175  4.762  1/4 x 1/2  0.15 (R188ZZ)  NSK; TFL (SKF); SKDIN, MBA\nR155  3.967  7.938  2.779  3.175  5/32 x 5/16  —  TFL (SKF)\nR156  4.763  7.938  2.779  3.175  3/16 x 5/16  —  TFL (SKF)\nR3  4.763  12.7  3.967  4.978  3/16 x 1/2  —  TFL (SKF); Emerson\nR3A  4.763  15.875  4.978  4.978  3/16 x 5/8  —  TFL (SKF)\nR168  6.35  9.525  3.175  3.175  1/4 x 3/8  —  TFL (SKF)\nR4  6.35  15.875  4.978  4.978  1/4 x 5/8  —  TFL (SKF); Emerson\nR4A  6.35  19.05  5.558  7.142  1/4 x 3/4  —  TFL (SKF); Emerson\nR6  9.525  22.225  5.558  7.142  3/8 x 7/8  —  TFL (SKF); Emerson\nR8  12.7  28.575  6.35  7.938  0.5000 x 1.1250 x 0.2500 / 0.3125  —  Emerson (mm = printed inch x 25.4)\nR10  15.875  34.925  7.142  8.733  0.6250 x 1.375 x 0.2812 / 0.3438  —  Emerson (mm = printed inch x 25.4)\nR12  19.05  41.275  7.938  11.113  0.7500 x 1.625 x 0.3125 / 0.4375  —  Emerson (mm = printed inch x 25.4)\nR14  22.225  47.625  9.525  12.7  0.8750 x 1.875 x 0.3750 / 0.5000  —  Emerson (mm = printed inch x 25.4)\nR16  25.4  50.8  9.525  12.7  1.0000 x 2.0000 x 0.3750 / 0.5000  —  Emerson (mm = printed inch x 25.4)\nR18  28.575  53.975  9.525  12.7  1.1250 x 2.125 x 0.3750 / 0.5000  —  Emerson (mm = printed inch x 25.4)\nR20  31.75  57.15  9.525  12.7  1.2500 x 2.250 x 0.3750 / 0.5000  —  Emerson (mm = printed inch x 25.4)\nR22  34.925  63.5  11.113  14.288  1.3750 x 2.5000 x 0.4375 / 0.5625  —  Emerson (mm = printed inch x 25.4)\nR24  38.1  66.675  11.113  14.288  1.5000 x 2.6250 x 0.4375 / 0.5625  —  Emerson (mm = printed inch x 25.4)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- NSK: Extra small and miniature ball bearings, inch series: d, D, B, r min (first 20 of 41 items: R09 to R2A) — web — Publisher's page; dimensions are facts — https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series.html\n- NSK: R166: d 4.762, D 9.525, B 3.175, r min 0.1 — web — Publisher's page; dimensions are facts — https://www.nsk.com/engineering/r166-esm-id.html\n- NSK: R144ZZ: d 3.175, D 6.35, B 2.779, r min 0.1 — web — Publisher's page; dimensions are facts — https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series/r144zz-esm-id.html\n- NSK: R188ZZ: d 6.35, D 12.7, B 4.762, r min 0.15; abutment db max 7.4, Db max 11.7, ra max 0.15 — web — Publisher's page; dimensions are facts — https://www.oss.nsk.com/r188zz-esm-id.html\n- Emerson Bearing: R-series miniature / instrumentation ball bearings R2 to R24: bore, OD, width (shielded / sealed and open) in inches — web — Publisher's page; dimensions are facts — https://products.emersonbearing.com/printitems/miniature-instrumentation-ball-bearings/r-series-miniature-instrumentation-ball-bearings?plpver=10\n- TFL Bearing (SKF catalogue designations): Miniature deep groove ball bearings of the series R in inch sizes: d, D, B in mm and inches, R1-4 to R6 and WR — web — Publisher's page; dimensions are facts — https://tflbearing.com/?p=5029\n- SKDIN (distributor): R188: 0.25 x 0.5 x 0.125 in (6.35 x 12.7 x 3.175 mm) — web — Publisher's page; dimensions are facts — https://www.skdin.com/products/productid-R188\n- MBA (miniaturebearings.com.au): R188AZZMC3: ID 6.350, OD 12.700, width 4.762 mm — web — Publisher's page; dimensions are facts — https://miniaturebearings.com.au/products/6-350x12-7x4-762-bearings-r188azzmc3\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 22 parts): https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/index.json\nAPI: https://xemstudio.com/api/geometry?object=inch-ball-bearings-r-series-r188-r144-r166\n",
 "sources": [
  {
   "publisher": "NSK",
   "title": "Extra small and miniature ball bearings, inch series: d, D, B, r min (first 20 of 41 items: R09 to R2A)",
   "url": "https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NSK",
   "title": "R166: d 4.762, D 9.525, B 3.175, r min 0.1",
   "url": "https://www.nsk.com/engineering/r166-esm-id.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NSK",
   "title": "R144ZZ: d 3.175, D 6.35, B 2.779, r min 0.1",
   "url": "https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series/r144zz-esm-id.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NSK",
   "title": "R188ZZ: d 6.35, D 12.7, B 4.762, r min 0.15; abutment db max 7.4, Db max 11.7, ra max 0.15",
   "url": "https://www.oss.nsk.com/r188zz-esm-id.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Emerson Bearing",
   "title": "R-series miniature / instrumentation ball bearings R2 to R24: bore, OD, width (shielded / sealed and open) in inches",
   "url": "https://products.emersonbearing.com/printitems/miniature-instrumentation-ball-bearings/r-series-miniature-instrumentation-ball-bearings?plpver=10",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "TFL Bearing (SKF catalogue designations)",
   "title": "Miniature deep groove ball bearings of the series R in inch sizes: d, D, B in mm and inches, R1-4 to R6 and WR",
   "url": "https://tflbearing.com/?p=5029",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "SKDIN (distributor)",
   "title": "R188: 0.25 x 0.5 x 0.125 in (6.35 x 12.7 x 3.175 mm)",
   "url": "https://www.skdin.com/products/productid-R188",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "MBA (miniaturebearings.com.au)",
   "title": "R188AZZMC3: ID 6.350, OD 12.700, width 4.762 mm",
   "url": "https://miniaturebearings.com.au/products/6-350x12-7x4-762-bearings-r188azzmc3",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "ball-bearings-metric",
  "deep-groove-ball-bearings-series",
  "ball-bearings-inch-1600-series",
  "flanged-ball-bearings-f6xx-mf",
  "608-bearing",
  "tapered-roller-bearings-inch-lm11949-l44649-lm67048",
  "retaining-rings-din-472-internal"
 ],
 "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": [
  {
   "feature": "R188ZZ shaft abutment Ø db (max)",
   "exact": "7.4 mm",
   "mates": "shaft shoulder diameter must not exceed this so the inner ring face is clear (NSK R188ZZ page)",
   "fit": "designed",
   "files": "R188ZZ"
  },
  {
   "feature": "R188ZZ housing abutment Ø Db (max)",
   "exact": "11.7 mm",
   "mates": "housing shoulder diameter must not exceed this so the outer ring face is clear (NSK)",
   "fit": "designed",
   "files": "R188ZZ"
  },
  {
   "feature": "R188ZZ fillet radius ra (max)",
   "exact": "0.15 mm",
   "mates": "shaft and housing corner fillet no larger than this (NSK)",
   "fit": "designed",
   "files": "R188ZZ"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. ISO 286 equivalent: H7/p6 (locational interference) or tighter.",
  "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. ISO 286 equivalent: H7/g6 or H7/h6.",
  "run": "turns or slides in use: pin in a link, rod through a guide. ISO 286 equivalent: H8/f7 (close running).",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. ISO 286 equivalent: H9/d9 (free running) or looser.",
  "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 are the dimensions of an R188 bearing?",
   "a": "Bore 1/4 in (6.35 mm), OD 1/2 in (12.7 mm), width 1/8 in (3.175 mm) open; the R188ZZ / 2Z / 2RS is 3/16 in (4.762 mm) wide."
  },
  {
   "q": "What are the dimensions of an R144 bearing?",
   "a": "Bore 3.175 mm (1/8 in), OD 6.35 mm (1/4 in), width 2.38 mm open and 2.779 mm for R144ZZ; r min 0.1 mm."
  },
  {
   "q": "What are the dimensions of an R166 bearing?",
   "a": "Bore 4.762 mm (3/16 in), OD 9.525 mm (3/8 in), width 3.175 mm (1/8 in); r min 0.1 mm."
  },
  {
   "q": "What are the dimensions of an R4 bearing?",
   "a": "Bore 6.35 mm (1/4 in), OD 15.875 mm (5/8 in), width 4.978 mm (0.196 in)."
  },
  {
   "q": "What are the dimensions of an R6 bearing?",
   "a": "Bore 9.525 mm (3/8 in), OD 22.225 mm (7/8 in), width 5.558 mm open and 7.142 mm shielded."
  }
 ],
 "files_license": null,
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   "note": "R09 inch-series miniature ball bearing ring envelope: bore Ø1.016, OD Ø3.175, width 1.191; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
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  },
  {
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   "note": "R0ZZ inch-series miniature ball bearing ring envelope: bore Ø1.191, OD Ø3.967, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
   "file": "R1-inch-miniature-ball-bearing-envelope-1.397x4.762x1.984",
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   "note": "R1 inch-series miniature ball bearing ring envelope: bore Ø1.397, OD Ø4.762, width 1.984; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
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   "note": "R1ZZ inch-series miniature ball bearing ring envelope: bore Ø1.397, OD Ø4.762, width 2.779; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
   "file": "R1-4-inch-miniature-ball-bearing-envelope-1.984x6.35x2.38",
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   "note": "R1-4 inch-series miniature ball bearing ring envelope: bore Ø1.984, OD Ø6.35, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
   "file": "R1-4ZZ-inch-miniature-ball-bearing-envelope-1.984x6.35x3.571",
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   "note": "R1-4ZZ inch-series miniature ball bearing ring envelope: bore Ø1.984, OD Ø6.35, width 3.571; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
  {
   "file": "R133-inch-miniature-ball-bearing-envelope-2.38x4.762x1.588",
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  },
  {
   "file": "R133ZZS-inch-miniature-ball-bearing-envelope-2.38x4.762x2.38",
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   "note": "R133ZZS inch-series miniature ball bearing ring envelope: bore Ø2.38, OD Ø4.762, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values"
  },
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  },
  {
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  },
  {
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  },
  {
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  },
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  },
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  },
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  },
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  },
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  },
  {
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  },
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   "step": "https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R188ZZ-inch-miniature-ball-bearing-envelope-6.35x12.7x4.762.step",
   "stl": "https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R188ZZ-inch-miniature-ball-bearing-envelope-6.35x12.7x4.762.stl",
   "note": "R188ZZ inch-series miniature ball bearing ring envelope: bore Ø6.35, OD Ø12.7, width 4.762; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values"
  }
 ],
 "markdown": "https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/index.md"
}