{
 "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-instrument-head",
 "name": "Tri-clamp instrument head: ISO 2852 cap with Ø6, Ø3 and Ø4 probe ports, 1.5, 2 and 3 in",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "How do I put a temperature probe through a tri-clamp end cap?",
 "tags": [
  "tri-clamp",
  "end cap",
  "ds18b20",
  "thermocouple",
  "instrumentation",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "tri clamp cap thermocouple port",
  "ds18b20 tri clamp",
  "tri clamp instrument cap",
  "temperature probe tri clamp end cap",
  "tri clamp sensor port"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/tri-clamp-instrument-head/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-instrument-head/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face with three ported bosses on the C2 − 16 circle, each with an M3 pinch hole (Ø2.5)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An ISO 2852 end cap with three probe ports, so a cylinder can be instrumented without drilling a flat cap.",
   "Ports: Ø6 (a DS18B20 sleeve), Ø3 (a K-type sheath) and Ø4 (a 4 mm tube), 120° apart on a circle of radius C2/2 − 8 (13.75 / 20.25 / 33.75 mm for 1.5 / 2 / 3 in).",
   "Each port has a boss 6 mm larger than its bore, 10 mm tall on the back of the 6 mm cap, and an Ø2.5 radial hole at 11 mm for an M3 pinch screw that holds the probe."
  ],
  "table": {
   "columns": [
    "size_in",
    "flange_od_mm",
    "port_circle_r_mm",
    "ports_mm",
    "pinch"
   ],
   "rows": [
    [
     "1.5",
     50.5,
     13.75,
     "Ø6 / Ø3 / Ø4",
     "M3 (Ø2.5)"
    ],
    [
     "2",
     64,
     20.25,
     "Ø6 / Ø3 / Ø4",
     "M3 (Ø2.5)"
    ],
    [
     "3",
     91,
     33.75,
     "Ø6 / Ø3 / Ø4",
     "M3 (Ø2.5)"
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp instrument head: ISO 2852 cap with Ø6, Ø3 and Ø4 probe ports, 1.5, 2 and 3 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-instrument-head/  (CC BY 4.0)\nBasis: ISO 2852 cap face with three ported bosses on the C2 − 16 circle, each with an M3 pinch hole (Ø2.5)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An ISO 2852 end cap with three probe ports, so a cylinder can be instrumented without drilling a flat cap.\n- Ports: Ø6 (a DS18B20 sleeve), Ø3 (a K-type sheath) and Ø4 (a 4 mm tube), 120° apart on a circle of radius C2/2 − 8 (13.75 / 20.25 / 33.75 mm for 1.5 / 2 / 3 in).\n- Each port has a boss 6 mm larger than its bore, 10 mm tall on the back of the 6 mm cap, and an Ø2.5 radial hole at 11 mm for an M3 pinch screw that holds the probe.\n\nsize_in  flange_od_mm  port_circle_r_mm  ports_mm  pinch\n1.5  50.5  13.75  Ø6 / Ø3 / Ø4  M3 (Ø2.5)\n2  64.0  20.25  Ø6 / Ø3 / Ø4  M3 (Ø2.5)\n3  91.0  33.75  Ø6 / Ø3 / Ø4  M3 (Ø2.5)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n- James R. Senft: An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-instrument-head/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-instrument-head\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Tri-clamp Stirling engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "James R. Senft",
   "title": "An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design)",
   "url": "https://www.stirlingengine.com/",
   "formats": [
    "book"
   ],
   "license": "Moriya Press",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Stirling engine",
   "url": "https://en.wikipedia.org/wiki/Stirling_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "probe-clamps",
  "tri-clamp-displacer-head",
  "tri-clamp-end-cap",
  "tri-clamp-clamps",
  "silicone-tube"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "ISO 2852 face on any ferrule of its size"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "probe-clamps",
     "why": "DS18B20 sleeve Ø6, K-type sheath Ø3"
    },
    {
     "slug": "silicone-tube",
     "why": "4 mm tube in the Ø4 port"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp and gasket on the face"
    }
   ]
  }
 ],
 "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": "head faces",
   "exact": "ISO 2852",
   "mates": "ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "head-"
  },
  {
   "feature": "probe / port bores",
   "exact": "Ø6 / Ø3 / Ø4",
   "mates": "DS18B20 sleeve / K-type sheath / 4 mm tube (M3 pinch)",
   "fit": "slide",
   "files": "head-instrument-"
  },
  {
   "feature": "pinch screw holes",
   "exact": "Ø2.5",
   "mates": "M3 tap drill",
   "fit": "designed",
   "files": "head-instrument-"
  }
 ],
 "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": "What probes fit the instrument head?",
   "a": "A Ø6 DS18B20 sleeve, a Ø3 K-type sheath and a 4 mm tube, each in its own bore with an M3 pinch screw."
  },
  {
   "q": "Where are the ports?",
   "a": "120° apart on a 20.25 mm radius on the 2 in head (13.75 on 1.5 in, 33.75 on 3 in)."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "head-instrument-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-1.5in.stl",
   "note": "1.5 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)"
  },
  {
   "file": "head-instrument-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-2in.stl",
   "note": "2 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)"
  },
  {
   "file": "head-instrument-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-3in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-3in.stl",
   "note": "3 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-instrument-head/index.md"
}