{
 "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": "bsp-thread-envelopes",
 "name": "BSP (G) male thread envelopes 1/8 to 1 in (ISO 228-1)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What is the outside diameter of a G1/4 BSP thread?",
 "tags": [
  "bsp",
  "bspp",
  "pipe thread",
  "thread",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "g1/2 thread od",
  "bsp thread sizes mm",
  "g1/4 major diameter",
  "bsp vs npt",
  "bspp dimensions"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/bsp-thread-envelopes/",
 "sheet_txt": "https://xemstudio.com/objects/bsp-thread-envelopes/sheet.txt",
 "sheet": {
  "basis": "ISO 228-1 (G, parallel) and ISO 7-1 (R / Rc, taper) BSP major diameters and TPI",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Each file is a plain cylinder at the BSPP (G) major OD, 14 mm long, with a 0.8 mm chamfer on the end; the thread form is not modelled.",
   "Major OD: G1/8 9.73, G1/4 13.16, G3/8 16.66, G1/2 20.96, G3/4 26.44, G1 33.25 mm; 28, 19, 19, 14, 14 and 11 TPI.",
   "BSP is a 55° thread; parallel G seals on a washer or O-ring, taper R on the thread.",
   "BSP and NPT do not interchange: 1/2 NPT is 14 TPI 60° and 21.34 OD, G1/2 is 14 TPI 55° and 20.96 OD."
  ],
  "table": {
   "columns": [
    "size",
    "od_mm",
    "tpi",
    "file_length_mm"
   ],
   "rows": [
    [
     "G1/8",
     9.73,
     28,
     14
    ],
    [
     "G1/4",
     13.16,
     19,
     14
    ],
    [
     "G3/8",
     16.66,
     19,
     14
    ],
    [
     "G1/2",
     20.96,
     14,
     14
    ],
    [
     "G3/4",
     26.44,
     14,
     14
    ],
    [
     "G1",
     33.25,
     11,
     14
    ]
   ]
  }
 },
 "sheet_text": "BSP (G) male thread envelopes 1/8 to 1 in (ISO 228-1) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/bsp-thread-envelopes/  (CC BY 4.0)\nBasis: ISO 228-1 (G, parallel) and ISO 7-1 (R / Rc, taper) BSP major diameters and TPI\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Each file is a plain cylinder at the BSPP (G) major OD, 14 mm long, with a 0.8 mm chamfer on the end; the thread form is not modelled.\n- Major OD: G1/8 9.73, G1/4 13.16, G3/8 16.66, G1/2 20.96, G3/4 26.44, G1 33.25 mm; 28, 19, 19, 14, 14 and 11 TPI.\n- BSP is a 55° thread; parallel G seals on a washer or O-ring, taper R on the thread.\n- BSP and NPT do not interchange: 1/2 NPT is 14 TPI 60° and 21.34 OD, G1/2 is 14 TPI 55° and 20.96 OD.\n\nsize  od_mm  tpi  file_length_mm\nG1/8  9.73  28  14\nG1/4  13.16  19  14\nG3/8  16.66  19  14\nG1/2  20.96  14  14\nG3/4  26.44  14  14\nG1  33.25  11  14\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: National pipe thread — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/National_pipe_thread\n- Wikipedia: British Standard Pipe — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/British_Standard_Pipe\n- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/bsp-thread-envelopes/index.json\nAPI: https://xemstudio.com/api/geometry?object=bsp-thread-envelopes\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "National pipe thread",
   "url": "https://en.wikipedia.org/wiki/National_pipe_thread",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "British Standard Pipe",
   "url": "https://en.wikipedia.org/wiki/British_Standard_Pipe",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds that use these parts (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": [
  "npt-thread-envelopes",
  "push-fit-fittings",
  "o-rings-metric"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "push-fit-fittings",
     "why": "G1/8 and G1/4 thread stubs on the push-fits"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "npt-thread-envelopes",
     "why": "NPT is 60° and taper; not interchangeable"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "o-rings-metric",
     "why": "parallel G threads seal on an O-ring or washer"
    }
   ]
  }
 ],
 "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 OD of G1/4?",
   "a": "13.16 mm, 19 TPI, 55° thread."
  },
  {
   "q": "Are NPT and BSP interchangeable?",
   "a": "No: NPT is 60° and BSP 55°, the ODs differ (1/2 NPT 21.34 vs G1/2 20.96 mm) and 1/8, 1/4 and 3/8 have different TPI."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "bsp-1-8-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-8-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-8-male.stl",
   "note": "G1/8 BSPP male, major OD 9.73 mm, 28 TPI, 14 mm; plain cylinder at OD"
  },
  {
   "file": "bsp-1-4-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-4-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-4-male.stl",
   "note": "G1/4 BSPP male, major OD 13.16 mm, 19 TPI, 14 mm; plain cylinder at OD"
  },
  {
   "file": "bsp-3-8-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-3-8-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-3-8-male.stl",
   "note": "G3/8 BSPP male, major OD 16.66 mm, 19 TPI, 14 mm; plain cylinder at OD"
  },
  {
   "file": "bsp-1-2-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-2-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-2-male.stl",
   "note": "G1/2 BSPP male, major OD 20.96 mm, 14 TPI, 14 mm; plain cylinder at OD"
  },
  {
   "file": "bsp-3-4-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-3-4-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-3-4-male.stl",
   "note": "G3/4 BSPP male, major OD 26.44 mm, 14 TPI, 14 mm; plain cylinder at OD"
  },
  {
   "file": "bsp-1-male",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-male.step",
   "stl": "https://xemstudio.com/files/hardware/npt-bsp-thread-envelopes/bsp-1-male.stl",
   "note": "G1 BSPP male, major OD 33.25 mm, 11 TPI, 14 mm; plain cylinder at OD"
  }
 ],
 "markdown": "https://xemstudio.com/objects/bsp-thread-envelopes/index.md"
}