{
 "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": "tri-clamp-transfer-cap",
 "name": "2 in end cap with a 1/2 NPT transfer boss, two 1/4 NPT bosses and a spigot (transfer cap)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I join two tri-clamp cylinders with a short gas passage?",
 "tags": [
  "cap",
  "end cap",
  "side port",
  "npt",
  "transfer",
  "custom cap",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "tri clamp cap with side port",
  "end cap with npt boss",
  "gamma transfer passage tri clamp"
 ],
 "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/tri-clamp-transfer-cap/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-transfer-cap/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 2 in face as on this site; 1/2 and 1/4 NPT per ASME B1.20.1; passages and spigot are design values",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A fabrication spec: a solid 2 in end cap with a 1/2 NPT boss on its side, two 1/4 NPT bosses and a spigot that fills the joint's dead space. Two of them, on two cylinders 120 mm apart with their transfer bosses facing, join with two 1/2 NPT × 1/2 in tube fittings and a 64 mm length of 1/2 in tube: the gamma's transfer passage.",
   "Gas path: spigot face → Ø11 axial passage (off-centre) → the 1/2 NPT port → fitting → tube (bore 10.9). Volume of the whole transfer path about 22.2 mL; its friction is in the engine's numbers.",
   "The rod-gland version carries the displacer rod in two 6 × 10 × 10 sleeve bushings 46 mm apart. The NPT bosses take the working space's fill valve, gauge, relief valve and a plug."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "face",
     "ISO 2852 2 in"
    ],
    [
     "spigot",
     "Ø44.0 to 3.15 past the face"
    ],
    [
     "transfer boss",
     "1/2 NPT, Ø30, face 28 from the axis, z 24"
    ],
    [
     "NPT",
     "2 × 1/4 at z 24, y 13, ±X"
    ],
    [
     "gland",
     "Ø10 seat z 30–86 (rod version)"
    ]
   ]
  }
 },
 "sheet_text": "2 in end cap with a 1/2 NPT transfer boss, two 1/4 NPT bosses and a spigot (transfer cap) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-transfer-cap/  (CC BY 4.0)\nBasis: ISO 2852 2 in face as on this site; 1/2 and 1/4 NPT per ASME B1.20.1; passages and spigot are design values\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A fabrication spec: a solid 2 in end cap with a 1/2 NPT boss on its side, two 1/4 NPT bosses and a spigot that fills the joint's dead space. Two of them, on two cylinders 120 mm apart with their transfer bosses facing, join with two 1/2 NPT × 1/2 in tube fittings and a 64 mm length of 1/2 in tube: the gamma's transfer passage.\n- Gas path: spigot face → Ø11 axial passage (off-centre) → the 1/2 NPT port → fitting → tube (bore 10.9). Volume of the whole transfer path about 22.2 mL; its friction is in the engine's numbers.\n- The rod-gland version carries the displacer rod in two 6 × 10 × 10 sleeve bushings 46 mm apart. The NPT bosses take the working space's fill valve, gauge, relief valve and a plug.\n\nfeature  value\nface  ISO 2852 2 in\nspigot  Ø44.0 to 3.15 past the face\ntransfer boss  1/2 NPT, Ø30, face 28 from the axis, z 24\nNPT  2 × 1/4 at z 24, y 13, ±X\ngland  Ø10 seat z 30–86 (rod version)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO (via iTeh sample): ISO 2852 clamp liners: face profile and flange / groove diameters — PDF — standard excerpt; dimensions are facts — https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf\n- ASME: BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall) — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment\n- ASME: ASME B1.20.1 Pipe Threads, General Purpose, Inch (NPT): 1/4-18 major Ø13.72, tap drill 7/16 in (11.1), L2 10.2 — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/b1-20-1-pipe-threads-general-purpose-inch\n- Long Earth Society: Engine builds — 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/tri-clamp-transfer-cap/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-transfer-cap\n",
 "sources": [
  {
   "publisher": "ISO (via iTeh sample)",
   "title": "ISO 2852 clamp liners: face profile and flange / groove diameters",
   "url": "https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf",
   "formats": [
    "PDF"
   ],
   "license": "standard excerpt; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "ASME",
   "title": "BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall)",
   "url": "https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment",
   "formats": [
    "standard"
   ],
   "license": "ASME; dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "ASME",
   "title": "ASME B1.20.1 Pipe Threads, General Purpose, Inch (NPT): 1/4-18 major Ø13.72, tap drill 7/16 in (11.1), L2 10.2",
   "url": "https://www.asme.org/codes-standards/find-codes-standards/b1-20-1-pipe-threads-general-purpose-inch",
   "formats": [
    "standard"
   ],
   "license": "ASME; dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds",
   "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": [
  "tri-clamp-closed-hot-spool-bored",
  "tri-clamp-spool-bored-honed",
  "list-tri-clamp-horizontal-gamma"
 ],
 "fits": [],
 "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": [
  {
   "feature": "face",
   "exact": "ISO 2852 2 in",
   "mates": "Type B gasket, 2 in clamp",
   "fit": "clamp",
   "files": "all"
  },
  {
   "feature": "spigot",
   "exact": "Ø44.0 to 3.15 past the face",
   "mates": "inside the gasket lip Ø45.3 (no contact)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "transfer boss",
   "exact": "1/2-14 NPT, tap drill Ø18.3 × 14",
   "mates": "1/2 NPT × 1/2 in tube fitting",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "port bosses",
   "exact": "2 × 1/4-18 NPT, tap drill Ø11.1 × 12",
   "mates": "gauge, relief valve, fill valve, plug",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "gland seat",
   "exact": "Ø10, z 30–86",
   "mates": "two 6 × 10 × 10 sleeve bushings",
   "fit": "press",
   "files": "transfer-cap-2in-rod6"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "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. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "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": "Why a spigot?",
   "a": "Without it the joint between the cap and the cylinder is a few mL of gas that does no work; the spigot fills it to within 0.5 mm of the liner."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "transfer-cap-2in-rod6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-transfer-cap/transfer-cap-2in-rod6.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-transfer-cap/transfer-cap-2in-rod6.stl",
   "note": "2 in transfer cap with rod gland: ISO 2852 face, body Ø50.8 × 40, spigot Ø44 to 3.15 past the face, Ø11 axial passage at y 13, 1/2 NPT transfer boss (+Y, face 28 from the axis, z 24), two 1/4 NPT bosses (±X, z 24), Ø10 seat z 30–86 for two 6 × 10 × 10 bushings"
  },
  {
   "file": "transfer-cap-2in-blind",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-transfer-cap/transfer-cap-2in-blind.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-transfer-cap/transfer-cap-2in-blind.stl",
   "note": "2 in transfer cap, blind: as the rod-gland cap without the gland boss"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-transfer-cap/index.md"
}