{
 "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": "rolling-parallel-ruler-mechanism",
 "name": "Rolling parallel ruler (blade on two notched rollers)",
 "kind": "hardware",
 "category": "Mechanisms",
 "group": "Linkages",
 "year": null,
 "question": "How does a rolling parallel ruler stay parallel?",
 "tags": [
  "mechanism",
  "linkages",
  "kinematics",
  "507 mechanical movements"
 ],
 "aliases": [
  "rolling parallel ruler",
  "rolling ruler",
  "roller parallel rule",
  "regla paralela de rodillos",
  "Rollparallellineal"
 ],
 "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/rolling-parallel-ruler-mechanism/",
 "sheet_txt": "https://xemstudio.com/objects/rolling-parallel-ruler-mechanism/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design following Brown No. 323 (1868)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A straight-edge carries an axle with a roller at each end; the rollers are the same size and fixed to the axle, so as the ruler rolls every point of the blade moves the same distance at right angles to the axle — the blade stays parallel to its starting line.",
   "The notched rims (24 V-notches, 0.85 mm deep) bite the paper so neither roller slips; the rollers stand 1 mm proud of the underside through openings in the blade. Drawn with a Ø3 × 150 axle, Ø18 × 4 rollers at ±60 mm and a 200 mm blade.",
   "Brown's No. 323 (rolling parallel ruler); the navigator's parallel rule.",
   "Parts (each has its own page): rolling-ruler-blade-200-d18, notched-roller-d18x4-b3, linear-shafts-h6.",
   "Brown's movement No. 323 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "blade",
     "200 × 24 × 6 mm"
    ],
    [
     "rollers",
     "2 × Ø18 × 4, notched"
    ],
    [
     "axle",
     "Ø3 × 150 (linear shaft)"
    ],
    [
     "roller spacing",
     "120 mm"
    ]
   ]
  }
 },
 "sheet_text": "Rolling parallel ruler (blade on two notched rollers) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/rolling-parallel-ruler-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Xem Studio design following Brown No. 323 (1868)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A straight-edge carries an axle with a roller at each end; the rollers are the same size and fixed to the axle, so as the ruler rolls every point of the blade moves the same distance at right angles to the axle — the blade stays parallel to its starting line.\n- The notched rims (24 V-notches, 0.85 mm deep) bite the paper so neither roller slips; the rollers stand 1 mm proud of the underside through openings in the blade. Drawn with a Ø3 × 150 axle, Ø18 × 4 rollers at ±60 mm and a 200 mm blade.\n- Brown's No. 323 (rolling parallel ruler); the navigator's parallel rule.\n- Parts (each has its own page): rolling-ruler-blade-200-d18, notched-roller-d18x4-b3, linear-shafts-h6.\n- Brown's movement No. 323 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.\n\nparameter  value\nblade  200 × 24 × 6 mm\nrollers  2 × Ø18 × 4, notched\naxle  Ø3 × 150 (linear shaft)\nroller spacing  120 mm\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- 507movements.com: Brown's movement No. 323: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_323.html\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/rolling-parallel-ruler-mechanism/index.json\nAPI: https://xemstudio.com/api/geometry?object=rolling-parallel-ruler-mechanism\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
  },
  {
   "publisher": "507movements.com",
   "title": "Brown's movement No. 323: figure, his text and an animation",
   "url": "https://507movements.com/mm_323.html",
   "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": [
  "rolling-ruler-blade-200-d18",
  "notched-roller-d18x4-b3",
  "linear-shafts-h6"
 ],
 "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 rolling parallel ruler stay parallel?",
   "a": "A straight-edge carries an axle with a roller at each end; the rollers are the same size and fixed to the axle, so as the ruler rolls every point of the blade moves the same distance at right angles to the axle — the blade stays parallel to its starting line."
  },
  {
   "q": "Why does a rolling ruler need equal rollers?",
   "a": "Unequal rollers would make the blade swing about the smaller one; equal, fixed rollers make every point travel the same distance."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
 "offers": [
  {
   "file": "rolling-parallel-ruler-mechanism-assembly",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/rolling-parallel-ruler-mechanism/rolling-parallel-ruler-mechanism-assembly.step",
   "stl": "https://xemstudio.com/files/hardware/rolling-parallel-ruler-mechanism/rolling-parallel-ruler-mechanism-assembly.stl",
   "note": "Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/rolling-parallel-ruler-mechanism/index.md"
}