{
 "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": "wood-screws-flat-head-inch",
 "name": "Flat-head wood screws, inch #4–#14 (ASME B18.6.1): body and head diameter, pilot and clearance holes from three sources + envelope models",
 "kind": "standard",
 "category": "Hardware",
 "group": "Fasteners",
 "year": null,
 "question": "What drill size for a #8 wood screw pilot and clearance hole, and what are the body and head diameters?",
 "tags": [
  "wood screw",
  "flat head wood screw",
  "pilot hole",
  "clearance hole",
  "drill size",
  "asme b18.6.1",
  "fastener",
  "countersunk"
 ],
 "aliases": [
  "wood screw pilot hole size",
  "#8 wood screw pilot hole",
  "#10 wood screw drill bit",
  "#6 wood screw clearance hole",
  "wood screw head diameter",
  "#8 flat head wood screw head diameter",
  "wood screw size chart",
  "#10 wood screw diameter",
  "b18.6.1 wood screw dimensions",
  "#8 screw pilot hole softwood hardwood",
  "#12 wood screw dimensions"
 ],
 "overall_mm": {
  "length": 38.1,
  "width": 12.9,
  "height": 12.9
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/wood-screws-flat-head-inch/",
 "sheet_txt": "https://xemstudio.com/objects/wood-screws-flat-head-inch/sheet.txt",
 "sheet": {
  "basis": "AFT Fasteners and Engineers Edge for the B18.6.1 body and flat-head dimensions (they agree), three pilot-hole sources (Albany County Fasteners, Fine Power Tools, Engineers Edge) that disagree and are shown side by side; six envelope models as files",
  "overall_mm": {
   "length": 38.1,
   "width": 12.9,
   "height": 12.9
  },
  "notes": [
   "Dimensions are inches, flat (countersunk) head slotted wood screws as printed on the B18.6.1 tables: threads per inch; nominal body diameter (Engineers Edge, = 0.060 + 0.013 × the screw number) with AFT's body max / min (Engineers Edge's note gives the tolerance as +0.004 / −0.007 for cut threads); flat head diameter A max / min and head height H (ref). The two tables agree on A, H and body diameter for every size #4 to #14; the mm column is the nominal body diameter converted, computed (× 25.4). AFT's table also prints a second diameter pair per size (smaller by about 0.02 in, not labelled clearly in the text read); it is not shown.",
   "Pilot and clearance holes are not part of the B18.6.1 table, and the three sources disagree, so all are shown. Albany County Fasteners: softwood / hardwood pilot and clearance for #4–#14. Fine Power Tools: its first table; the page also carries a second, extended table with other values (it gives 1/16 for #4 softwood and 1/8 for #8 hardwood) that is not used. Engineers Edge: hardwood / softwood pilot only, listed there as per B18.6.1. Examples of the spread: #4 softwood pilot 5/64 (Albany) against 3/64 (Fine Power Tools and Engineers Edge); #8 softwood 7/64 against 5/64; #10 hardwood 9/64 (Albany, Fine Power Tools) against 7/64 (Engineers Edge). Clearance holes agree between Albany and Fine Power Tools for #6 to #14 (9/64, 11/64, 3/16, 7/32, 1/4) and differ for #4 (1/8 against 7/64). Pilot sizes depend on the wood and screw design: use the maker's chart for your screw.",
   "Files are Xem-drawn envelopes, not the real screw: the flat head is a cone from the head diameter A max (top) down to the nominal body diameter over H ref (the cone angle follows from those numbers); the body is a plain cylinder at the nominal diameter (the real thread is smaller at the root); no slot or recess, no gimlet point. The overall length 1-1/2 in (38.1 mm) is an example chosen by Xem for all six files, not a published length. The head top is flat.",
   "Not on this page: round, oval, pan and other heads (B18.6.1 covers them), slot and recess dimensions, thread length. Metric chipboard / wood screws 3–6 mm: no table could be verified (McMaster's metric wood-screw listings are hex-head thread-forming M6 to M16 and are lag-type screws, not this size range), so none is shown. McMaster-Carr sells wood screws with per-part STEP; its category is linked, not copied. Hex lag screws: lag-screws-hex-inch."
  ],
  "table": {
   "columns": [
    "screw #",
    "TPI",
    "nominal body dia (in)",
    "nominal body dia (mm, computed)",
    "body dia max / min (AFT, in)",
    "flat head dia A max / min (in)",
    "head height H ref (in)",
    "pilot softwood / hardwood (Albany, in)",
    "clearance (Albany, in)",
    "pilot softwood / hardwood (Fine Power Tools, in)",
    "clearance (Fine Power Tools, in)",
    "pilot hardwood / softwood (Engineers Edge, in)"
   ],
   "rows": [
    [
     "#4",
     "22",
     ".112",
     "2.84",
     ".116 / .105",
     ".225 / .195",
     ".067",
     "5/64 / 3/32",
     "1/8",
     "3/64 / 5/64",
     "7/64",
     "1/16 / 3/64"
    ],
    [
     "#5",
     "20",
     ".125",
     "3.17",
     ".129 / .118",
     ".252 / .220",
     ".075",
     "5/64 / 3/32",
     "9/64",
     "—",
     "—",
     "—"
    ],
    [
     "#6",
     "18",
     ".138",
     "3.51",
     ".142 / .131",
     ".279 / .244",
     ".083",
     "3/32 / 7/64",
     "9/64",
     "1/16 / 3/32",
     "9/64",
     "5/64 / 1/16"
    ],
    [
     "#7",
     "16",
     ".151",
     "3.84",
     ".155 / .144",
     ".305 / .268",
     ".091",
     "3/32 / 7/64",
     "5/32",
     "—",
     "—",
     "—"
    ],
    [
     "#8",
     "15",
     ".164",
     "4.17",
     ".168 / .157",
     ".332 / .292",
     ".100",
     "7/64 / 1/8",
     "11/64",
     "5/64 / 7/64",
     "11/64",
     "3/32 / 5/64"
    ],
    [
     "#9",
     "14",
     ".177",
     "4.50",
     ".181 / .170",
     ".358 / .316",
     ".108",
     "7/64 / 1/8",
     "3/16",
     "—",
     "—",
     "—"
    ],
    [
     "#10",
     "13",
     ".190",
     "4.83",
     ".194 / .183",
     ".385 / .340",
     ".116",
     "1/8 / 9/64",
     "3/16",
     "3/32 / 9/64",
     "3/16",
     "7/64 / 3/32"
    ],
    [
     "#12",
     "11",
     ".216",
     "5.49",
     ".220 / .209",
     ".438 / .389",
     ".132",
     "9/64 / 5/32",
     "7/32",
     "7/64 / 5/32",
     "7/32",
     "1/8 / 7/64"
    ],
    [
     "#14",
     "10",
     ".242",
     "6.15",
     ".246 / .235",
     ".507 / .452",
     ".153",
     "5/32 / 3/16",
     "1/4",
     "5/32 / 11/64",
     "1/4",
     "9/64 / 1/8"
    ]
   ]
  }
 },
 "sheet_text": "Flat-head wood screws, inch #4–#14 (ASME B18.6.1): body and head diameter, pilot and clearance holes from three sources + envelope models — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/wood-screws-flat-head-inch/  (sheet CC BY 4.0)\nBasis: AFT Fasteners and Engineers Edge for the B18.6.1 body and flat-head dimensions (they agree), three pilot-hole sources (Albany County Fasteners, Fine Power Tools, Engineers Edge) that disagree and are shown side by side; six envelope models as files\nCatalog version: 2026-10-20\n\nOverall (mm): length 38.1, width 12.9, height 12.9\n- Dimensions are inches, flat (countersunk) head slotted wood screws as printed on the B18.6.1 tables: threads per inch; nominal body diameter (Engineers Edge, = 0.060 + 0.013 × the screw number) with AFT's body max / min (Engineers Edge's note gives the tolerance as +0.004 / −0.007 for cut threads); flat head diameter A max / min and head height H (ref). The two tables agree on A, H and body diameter for every size #4 to #14; the mm column is the nominal body diameter converted, computed (× 25.4). AFT's table also prints a second diameter pair per size (smaller by about 0.02 in, not labelled clearly in the text read); it is not shown.\n- Pilot and clearance holes are not part of the B18.6.1 table, and the three sources disagree, so all are shown. Albany County Fasteners: softwood / hardwood pilot and clearance for #4–#14. Fine Power Tools: its first table; the page also carries a second, extended table with other values (it gives 1/16 for #4 softwood and 1/8 for #8 hardwood) that is not used. Engineers Edge: hardwood / softwood pilot only, listed there as per B18.6.1. Examples of the spread: #4 softwood pilot 5/64 (Albany) against 3/64 (Fine Power Tools and Engineers Edge); #8 softwood 7/64 against 5/64; #10 hardwood 9/64 (Albany, Fine Power Tools) against 7/64 (Engineers Edge). Clearance holes agree between Albany and Fine Power Tools for #6 to #14 (9/64, 11/64, 3/16, 7/32, 1/4) and differ for #4 (1/8 against 7/64). Pilot sizes depend on the wood and screw design: use the maker's chart for your screw.\n- Files are Xem-drawn envelopes, not the real screw: the flat head is a cone from the head diameter A max (top) down to the nominal body diameter over H ref (the cone angle follows from those numbers); the body is a plain cylinder at the nominal diameter (the real thread is smaller at the root); no slot or recess, no gimlet point. The overall length 1-1/2 in (38.1 mm) is an example chosen by Xem for all six files, not a published length. The head top is flat.\n- Not on this page: round, oval, pan and other heads (B18.6.1 covers them), slot and recess dimensions, thread length. Metric chipboard / wood screws 3–6 mm: no table could be verified (McMaster's metric wood-screw listings are hex-head thread-forming M6 to M16 and are lag-type screws, not this size range), so none is shown. McMaster-Carr sells wood screws with per-part STEP; its category is linked, not copied. Hex lag screws: lag-screws-hex-inch.\n\nscrew #  TPI  nominal body dia (in)  nominal body dia (mm, computed)  body dia max / min (AFT, in)  flat head dia A max / min (in)  head height H ref (in)  pilot softwood / hardwood (Albany, in)  clearance (Albany, in)  pilot softwood / hardwood (Fine Power Tools, in)  clearance (Fine Power Tools, in)  pilot hardwood / softwood (Engineers Edge, in)\n#4  22  .112  2.84  .116 / .105  .225 / .195  .067  5/64 / 3/32  1/8  3/64 / 5/64  7/64  1/16 / 3/64\n#5  20  .125  3.17  .129 / .118  .252 / .220  .075  5/64 / 3/32  9/64  —  —  —\n#6  18  .138  3.51  .142 / .131  .279 / .244  .083  3/32 / 7/64  9/64  1/16 / 3/32  9/64  5/64 / 1/16\n#7  16  .151  3.84  .155 / .144  .305 / .268  .091  3/32 / 7/64  5/32  —  —  —\n#8  15  .164  4.17  .168 / .157  .332 / .292  .100  7/64 / 1/8  11/64  5/64 / 7/64  11/64  3/32 / 5/64\n#9  14  .177  4.50  .181 / .170  .358 / .316  .108  7/64 / 1/8  3/16  —  —  —\n#10  13  .190  4.83  .194 / .183  .385 / .340  .116  1/8 / 9/64  3/16  3/32 / 9/64  3/16  7/64 / 3/32\n#12  11  .216  5.49  .220 / .209  .438 / .389  .132  9/64 / 5/32  7/32  7/64 / 5/32  7/32  1/8 / 7/64\n#14  10  .242  6.15  .246 / .235  .507 / .452  .153  5/32 / 3/16  1/4  5/32 / 11/64  1/4  9/64 / 1/8\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- AFT Fasteners: Wood screws dimensions and mechanical specs (ASME B18.6.1): nominal size, threads per inch, body diameter max / min, flat head diameter A, head height H — web — Publisher's page; dimensions are facts — https://www.aftfasteners.com/wood-screws-dimensions-mechanical-specs/\n- Engineers Edge: ANSI B18.6.1 wood screw dimensions: threads per inch, body diameter, flat head diameter A max / min, head height H — web — Publisher's page; dimensions are facts — https://ns2.engineersedge.com/hardware/ansi_wood_screws_per_ansi_b1861__14855.htm\n- Albany County Fasteners: Wood screw pilot hole guide: softwood pilot, hardwood pilot, clearance hole by screw size #2 to 5/16 — web — Distributor guide; numbers only — https://www.albanycountyfasteners.com/media/51/31/8c/1764682594/wood-screw-pilot-hole-guide.pdf\n- Fine Power Tools: What size drill bit for a screw: softwood pilot, hardwood pilot, shank clearance hole #4 to #14 — web — Tool-review page; numbers only (its second table has other values) — https://www.finepowertools.com/woodworking/what-size-drill-bit-for-screw/\n- Engineers Edge: Pilot hole drill sizes for wood screws, hardwood and softwood, #2 to #14 (page says per ANSI B18.6.1) — web — Publisher's page; dimensions are facts — https://engineersedge.com/hardware/pilot_hole_drill_sizes_wood_screws_14857.htm\n- McMaster-Carr: Wood screws (free STEP/IGES per part, for your own design use; no redistribution) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution [verify license at link] — https://www.mcmaster.com/wood-screws\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/wood-screws-flat-head-inch/index.json\nAPI: https://xemstudio.com/api/geometry?object=wood-screws-flat-head-inch\n",
 "sources": [
  {
   "publisher": "AFT Fasteners",
   "title": "Wood screws dimensions and mechanical specs (ASME B18.6.1): nominal size, threads per inch, body diameter max / min, flat head diameter A, head height H",
   "url": "https://www.aftfasteners.com/wood-screws-dimensions-mechanical-specs/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Engineers Edge",
   "title": "ANSI B18.6.1 wood screw dimensions: threads per inch, body diameter, flat head diameter A max / min, head height H",
   "url": "https://ns2.engineersedge.com/hardware/ansi_wood_screws_per_ansi_b1861__14855.htm",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Albany County Fasteners",
   "title": "Wood screw pilot hole guide: softwood pilot, hardwood pilot, clearance hole by screw size #2 to 5/16",
   "url": "https://www.albanycountyfasteners.com/media/51/31/8c/1764682594/wood-screw-pilot-hole-guide.pdf",
   "formats": [
    "web"
   ],
   "license": "Distributor guide; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Fine Power Tools",
   "title": "What size drill bit for a screw: softwood pilot, hardwood pilot, shank clearance hole #4 to #14",
   "url": "https://www.finepowertools.com/woodworking/what-size-drill-bit-for-screw/",
   "formats": [
    "web"
   ],
   "license": "Tool-review page; numbers only (its second table has other values)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Engineers Edge",
   "title": "Pilot hole drill sizes for wood screws, hardwood and softwood, #2 to #14 (page says per ANSI B18.6.1)",
   "url": "https://engineersedge.com/hardware/pilot_hole_drill_sizes_wood_screws_14857.htm",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Wood screws (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/wood-screws",
   "formats": [
    "STEP",
    "IGES",
    "PDF"
   ],
   "license": "McMaster-Carr site terms: personal design use, no redistribution",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "lag-screws-hex-inch",
  "countersunk-screws-metric",
  "imperial-machine-screws",
  "hex-bolts-inch",
  "socket-head-cap-screws-inch"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no tolerance added)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no tolerance added. 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. Typical accuracy by process and ISO 286 fits: https://xemstudio.com/tolerances/",
 "mating": [],
 "faq": [
  {
   "q": "What is the head diameter of a #8 flat-head wood screw?",
   "a": "0.332 in max and 0.292 in min (A) in both AFT's and Engineers Edge's B18.6.1 tables; head height H 0.100 in (ref)."
  },
  {
   "q": "What clearance hole for a #8 wood screw?",
   "a": "11/64 in in both Albany County Fasteners' and Fine Power Tools' tables."
  },
  {
   "q": "What pilot hole for a #8 wood screw?",
   "a": "The sources disagree. Softwood: 7/64 (Albany), 5/64 (Fine Power Tools), 5/64 (Engineers Edge). Hardwood: 1/8 (Albany), 7/64 (Fine Power Tools), 3/32 (Engineers Edge). Check the screw maker's chart."
  }
 ],
 "files_license": null,
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   "note": "#4 flat-head wood screw envelope: head Ø5.71 mm (A max .225 in) tapering to the Ø2.845 mm nominal body over 1.70 mm (H ref .067 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
  },
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   "note": "#6 flat-head wood screw envelope: head Ø7.09 mm (A max .279 in) tapering to the Ø3.505 mm nominal body over 2.11 mm (H ref .083 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
  },
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   "note": "#8 flat-head wood screw envelope: head Ø8.43 mm (A max .332 in) tapering to the Ø4.166 mm nominal body over 2.54 mm (H ref .100 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
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   "note": "#10 flat-head wood screw envelope: head Ø9.78 mm (A max .385 in) tapering to the Ø4.826 mm nominal body over 2.95 mm (H ref .116 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
  },
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   "note": "#12 flat-head wood screw envelope: head Ø11.13 mm (A max .438 in) tapering to the Ø5.486 mm nominal body over 3.35 mm (H ref .132 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
  },
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   "note": "#14 flat-head wood screw envelope: head Ø12.88 mm (A max .507 in) tapering to the Ø6.147 mm nominal body over 3.89 mm (H ref .153 in); plain body, example overall length 1-1/2 in (38.1 mm, Xem's choice); no thread, slot, recess or point"
  }
 ],
 "markdown": "https://xemstudio.com/objects/wood-screws-flat-head-inch/index.md"
}