{
 "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": "crank-slotted-lever-quick-return",
 "name": "Crank and slotted lever quick-return mechanism",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Linkages",
 "year": null,
 "question": "How does a quick-return mechanism work?",
 "tags": [
  "mechanism",
  "linkages",
  "kinematics"
 ],
 "aliases": [
  "quick return mechanism",
  "crank and slotted lever",
  "whitworth quick return",
  "shaper mechanism"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/crank-slotted-lever-quick-return/",
 "sheet_txt": "https://xemstudio.com/objects/crank-slotted-lever-quick-return/sheet.txt",
 "sheet": {
  "basis": "Xem Studio drawing; classic mechanism (Brown No. 100)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A crank of radius r turns about a centre a distance d from the lever pivot; its pin, in a slide block, drives a slotted lever. The lever reaches its ends when the crank is square to it, at crank angles ±acos(r/d).",
   "Return stroke takes 2·acos(r/d) of crank rotation, the working stroke the rest: time ratio = (360° − 2·acos(r/d)) / (2·acos(r/d)) = 2 : 1 for r = 25, d = 50 mm.",
   "Shaping machines use it: slow cut, fast return. Whitworth's version puts the crank pivot inside the lever's path so the lever turns fully round.",
   "Parts (each has its own page): crank-discs-5mm-bore, slotted-lever-140, slide-block-12x6, pins-3mm. Brown's movement No. 100 shows it (1868)."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "crank radius r",
     "25 mm"
    ],
    [
     "pivot distance d",
     "50 mm"
    ],
    [
     "time ratio",
     "2 : 1"
    ],
    [
     "lever",
     "140 mm slotted"
    ]
   ]
  }
 },
 "sheet_text": "Crank and slotted lever quick-return mechanism — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/crank-slotted-lever-quick-return/  (CC BY 4.0)\nBasis: Xem Studio drawing; classic mechanism (Brown No. 100)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A crank of radius r turns about a centre a distance d from the lever pivot; its pin, in a slide block, drives a slotted lever. The lever reaches its ends when the crank is square to it, at crank angles ±acos(r/d).\n- Return stroke takes 2·acos(r/d) of crank rotation, the working stroke the rest: time ratio = (360° − 2·acos(r/d)) / (2·acos(r/d)) = 2 : 1 for r = 25, d = 50 mm.\n- Shaping machines use it: slow cut, fast return. Whitworth's version puts the crank pivot inside the lever's path so the lever turns fully round.\n- Parts (each has its own page): crank-discs-5mm-bore, slotted-lever-140, slide-block-12x6, pins-3mm. Brown's movement No. 100 shows it (1868).\n\nparameter  value\ncrank radius r  25 mm\npivot distance d  50 mm\ntime ratio  2 : 1\nlever  140 mm slotted\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/crank-slotted-lever-quick-return/index.json\nAPI: https://xemstudio.com/api/geometry?object=crank-slotted-lever-quick-return\n",
 "sources": [
  {
   "publisher": "Henry T. Brown (1868, public domain)",
   "title": "Five Hundred and Seven Mechanical Movements — scan on archive.org",
   "url": "https://archive.org/details/fivehundredseven00browiala",
   "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": [
  "crank-discs-5mm-bore",
  "slotted-lever-140",
  "slide-block-12x6",
  "pins-3mm"
 ],
 "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": [],
 "faq": [
  {
   "q": "How does a quick-return mechanism work?",
   "a": "A crank of radius r turns about a centre a distance d from the lever pivot; its pin, in a slide block, drives a slotted lever. The lever reaches its ends when the crank is square to it, at crank angles ±acos(r/d)."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-slotted-lever-quick-return-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-slotted-lever-quick-return/crank-slotted-lever-quick-return-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/crank-slotted-lever-quick-return/crank-slotted-lever-quick-return-assembly.stl",
   "note": "Assembled mechanism, all parts placed (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/crank-slotted-lever-quick-return/index.md"
}