{
 "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": "deck-screws-8-10-simpson-grk",
 "name": "Deck screws #8 and #10: head diameter (0.330 / 0.34 in), six-lobe drive (T20 / T25) and lengths for Simpson Deck-Drive, DWP stainless and GRK",
 "kind": "standard",
 "category": "Hardware",
 "group": "Fasteners",
 "year": null,
 "question": "What is the head diameter and drive size of a #8 or #10 deck screw (T20 or T25), and what lengths do they come in?",
 "tags": [
  "deck screw",
  "decking screw",
  "t25 deck screw",
  "t20 deck screw",
  "grk screw",
  "simpson dsv",
  "6 lobe screw",
  "star drive deck screw",
  "#10 deck screw",
  "#8 deck screw",
  "tool"
 ],
 "aliases": [
  "#10 deck screw head diameter",
  "#8 deck screw dimensions",
  "what size bit for deck screws",
  "t25 deck screw size",
  "deck screw sizes chart",
  "simpson dsv head diameter",
  "#10 x 3 deck screw dimensions",
  "deck screw drive size",
  "#8 wood screw head diameter deck",
  "trim head deck screw head diameter",
  "dwp wood ss head diameter",
  "deck screw bit size t20 t25"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/deck-screws-8-10-simpson-grk/",
 "sheet_txt": "https://xemstudio.com/objects/deck-screws-8-10-simpson-grk/sheet.txt",
 "sheet": {
  "basis": "Simpson Strong-Tie's Deck-Drive DSV catalog entries (via SC Fastening) and its DWP Wood SS data sheet, GRK's sell sheet (sizes and lengths only), Grabber's basic-diameter table and a SPAX 4.0 mm listing; numbers only",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Inches unless stated. 'Deck screw' is not a standard: the sizes here are what the makers print. Simpson prints a head diameter of 0.330 in for both the #10 × 2 in and the #8 × 1-1/4 in Deck-Drive DSV (T25 six-lobe, rimmed flat head with nibs, variable thread, high-low point), and 0.34 in for the flat-head DWP Wood SS #8 (T20) and #10 (T25) stainless screws; trim heads are 0.23 in (#7, T15), 0.25 in (#8 and #9, T20) and 0.26 in (#8 Quik Drive painted trim, T20). 0.330 and 0.34 are two makers' lines, not a tolerance range; the sheets give no tolerance.",
   "Basic screw diameter from Grabber's selection guide: #8 = 0.1640 in and #10 = 0.1900 in (4.17 and 4.83 mm). Thread major, root diameter, thread length, shank diameter and pilot-hole diameters are not printed on any sheet read here, so none is shown; GRK's sell sheet refers to its own product documentation and ICC-ES reports for those. A SPAX universal screw listing prints 4.0 mm thread and 8.0 mm head with a T20 drive and says it needs no pre-drilling in some woods.",
   "'Drive' is the hexalobular (Torx) size as the makers print it: T20 and T25 correspond to ISO 10664 sockets 20 and 25; see torx-hexalobular-drive-sizes-iso-10664 for A and B. GRK prints star drive without a size in the sheet read.",
   "No file: head profile (rim, nibs, bugle or cone), thread form and point are not published as numbers in the sources read. Simpson's catalog page is linked as the maker's product listing; its CAD availability was not checked.",
   "Wood screws, inch: wood-screws-flat-head-inch (ASME B18.6.1 head and pilot holes); lag screws: lag-screws-hex-inch; metric chipboard screws: chipboard-wood-screws-din-7505."
  ],
  "table": {
   "columns": [
    "line",
    "size",
    "head diameter (in)",
    "head style",
    "drive",
    "lengths (in)"
   ],
   "rows": [
    [
     "Simpson Deck-Drive DSV (catalog item DSVR2MB, #10 x 2)",
     "#10",
     "0.330",
     "rimmed flat head with nibs",
     "T25 six-lobe",
     "2 (item read); other lengths exist"
    ],
    [
     "Simpson Deck-Drive DSV (catalog item DSVT114R5LB, #8 x 1-1/4)",
     "#8",
     "0.330",
     "rimmed flat head with nibs",
     "T25 six-lobe",
     "1-1/4 (item read); other lengths exist"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 316 SS, flat",
     "#8",
     "0.34",
     "flat",
     "T20",
     "1-1/4, 1-5/8, 2, 2-1/2, 3"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 316 SS, flat",
     "#10",
     "0.34",
     "flat",
     "T25",
     "2, 2-1/2, 3, 3-1/2, 4-1/2"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 305 SS, flat",
     "#8",
     "0.34",
     "flat",
     "T20",
     "1-1/4, 1-5/8, 2, 2-1/2, 3"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 305 SS, flat",
     "#10",
     "0.34",
     "flat",
     "T25",
     "1, 1-1/2, 2, 2-1/2, 3, 3-1/2"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 305 SS, trim",
     "#7",
     "0.23",
     "trim",
     "T15",
     "1, 1-1/4, 1-5/8, 2, 2-1/4, 2-1/2, 3"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 305 SS, trim",
     "#8",
     "0.25",
     "trim",
     "T20",
     "2-1/2, 3"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 305 SS, trim",
     "#9",
     "0.25",
     "trim",
     "T20",
     "3-1/2, 4"
    ],
    [
     "Simpson Deck-Drive DWP Wood SS, 316 SS, trim",
     "#7",
     "0.23",
     "trim",
     "T15",
     "1-5/8, 2-1/4, 3"
    ],
    [
     "Simpson DWP Wood SS, painted heads, trim",
     "#7",
     "0.23",
     "trim (316 SS)",
     "T15",
     "2-1/4, 3"
    ],
    [
     "Simpson DWP Wood SS, painted heads, trim",
     "#10",
     "0.34",
     "trim (305 SS)",
     "T25",
     "2-1/2, 3"
    ],
    [
     "Simpson DWP Wood SS, painted heads, flat",
     "#10",
     "0.34",
     "flat (305 SS)",
     "T25",
     "2-1/2, 3"
    ],
    [
     "Simpson DWP Wood SS, painted heads, trim (Quik Drive)",
     "#8",
     "0.26",
     "trim (305 SS)",
     "T20 (Quik Drive collated screws use BITTX25 per the sheet)",
     "2-1/2"
    ],
    [
     "GRK R4 multi-purpose (sell sheet)",
     "#8 / #9 / #10 / #12",
     "not in the sheet",
     "—",
     "star drive (not sized in the sheet)",
     "#8 1-1/2 to 2; #9 1-1/2 to 3-1/8; #10 2-1/2 to 4-3/4; #12 5-5/8 to 6-3/8"
    ],
    [
     "GRK Fin/Trim head (sell sheet)",
     "#8 / #9",
     "not in the sheet",
     "trim",
     "star drive (not sized in the sheet)",
     "#8 1-1/2 to 3-1/8; #9 4, 5"
    ],
    [
     "GRK RT composite Fin/Trim (sell sheet)",
     "#8",
     "not in the sheet",
     "trim",
     "star drive (not sized in the sheet)",
     "2, 2-1/2, 3-1/8"
    ],
    [
     "Basic screw diameters (Grabber selection guide)",
     "#8 / #10",
     "—",
     "—",
     "—",
     "#8 0.1640 in, #10 0.1900 in (basic screw diameter)"
    ]
   ]
  }
 },
 "sheet_text": "Deck screws #8 and #10: head diameter (0.330 / 0.34 in), six-lobe drive (T20 / T25) and lengths for Simpson Deck-Drive, DWP stainless and GRK — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/deck-screws-8-10-simpson-grk/  (sheet CC BY 4.0)\nBasis: Simpson Strong-Tie's Deck-Drive DSV catalog entries (via SC Fastening) and its DWP Wood SS data sheet, GRK's sell sheet (sizes and lengths only), Grabber's basic-diameter table and a SPAX 4.0 mm listing; numbers only\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Inches unless stated. 'Deck screw' is not a standard: the sizes here are what the makers print. Simpson prints a head diameter of 0.330 in for both the #10 × 2 in and the #8 × 1-1/4 in Deck-Drive DSV (T25 six-lobe, rimmed flat head with nibs, variable thread, high-low point), and 0.34 in for the flat-head DWP Wood SS #8 (T20) and #10 (T25) stainless screws; trim heads are 0.23 in (#7, T15), 0.25 in (#8 and #9, T20) and 0.26 in (#8 Quik Drive painted trim, T20). 0.330 and 0.34 are two makers' lines, not a tolerance range; the sheets give no tolerance.\n- Basic screw diameter from Grabber's selection guide: #8 = 0.1640 in and #10 = 0.1900 in (4.17 and 4.83 mm). Thread major, root diameter, thread length, shank diameter and pilot-hole diameters are not printed on any sheet read here, so none is shown; GRK's sell sheet refers to its own product documentation and ICC-ES reports for those. A SPAX universal screw listing prints 4.0 mm thread and 8.0 mm head with a T20 drive and says it needs no pre-drilling in some woods.\n- 'Drive' is the hexalobular (Torx) size as the makers print it: T20 and T25 correspond to ISO 10664 sockets 20 and 25; see torx-hexalobular-drive-sizes-iso-10664 for A and B. GRK prints star drive without a size in the sheet read.\n- No file: head profile (rim, nibs, bugle or cone), thread form and point are not published as numbers in the sources read. Simpson's catalog page is linked as the maker's product listing; its CAD availability was not checked.\n- Wood screws, inch: wood-screws-flat-head-inch (ASME B18.6.1 head and pilot holes); lag screws: lag-screws-hex-inch; metric chipboard screws: chipboard-wood-screws-din-7505.\n\nline  size  head diameter (in)  head style  drive  lengths (in)\nSimpson Deck-Drive DSV (catalog item DSVR2MB, #10 x 2)  #10  0.330  rimmed flat head with nibs  T25 six-lobe  2 (item read); other lengths exist\nSimpson Deck-Drive DSV (catalog item DSVT114R5LB, #8 x 1-1/4)  #8  0.330  rimmed flat head with nibs  T25 six-lobe  1-1/4 (item read); other lengths exist\nSimpson Deck-Drive DWP Wood SS, 316 SS, flat  #8  0.34  flat  T20  1-1/4, 1-5/8, 2, 2-1/2, 3\nSimpson Deck-Drive DWP Wood SS, 316 SS, flat  #10  0.34  flat  T25  2, 2-1/2, 3, 3-1/2, 4-1/2\nSimpson Deck-Drive DWP Wood SS, 305 SS, flat  #8  0.34  flat  T20  1-1/4, 1-5/8, 2, 2-1/2, 3\nSimpson Deck-Drive DWP Wood SS, 305 SS, flat  #10  0.34  flat  T25  1, 1-1/2, 2, 2-1/2, 3, 3-1/2\nSimpson Deck-Drive DWP Wood SS, 305 SS, trim  #7  0.23  trim  T15  1, 1-1/4, 1-5/8, 2, 2-1/4, 2-1/2, 3\nSimpson Deck-Drive DWP Wood SS, 305 SS, trim  #8  0.25  trim  T20  2-1/2, 3\nSimpson Deck-Drive DWP Wood SS, 305 SS, trim  #9  0.25  trim  T20  3-1/2, 4\nSimpson Deck-Drive DWP Wood SS, 316 SS, trim  #7  0.23  trim  T15  1-5/8, 2-1/4, 3\nSimpson DWP Wood SS, painted heads, trim  #7  0.23  trim (316 SS)  T15  2-1/4, 3\nSimpson DWP Wood SS, painted heads, trim  #10  0.34  trim (305 SS)  T25  2-1/2, 3\nSimpson DWP Wood SS, painted heads, flat  #10  0.34  flat (305 SS)  T25  2-1/2, 3\nSimpson DWP Wood SS, painted heads, trim (Quik Drive)  #8  0.26  trim (305 SS)  T20 (Quik Drive collated screws use BITTX25 per the sheet)  2-1/2\nGRK R4 multi-purpose (sell sheet)  #8 / #9 / #10 / #12  not in the sheet  —  star drive (not sized in the sheet)  #8 1-1/2 to 2; #9 1-1/2 to 3-1/8; #10 2-1/2 to 4-3/4; #12 5-5/8 to 6-3/8\nGRK Fin/Trim head (sell sheet)  #8 / #9  not in the sheet  trim  star drive (not sized in the sheet)  #8 1-1/2 to 3-1/8; #9 4, 5\nGRK RT composite Fin/Trim (sell sheet)  #8  not in the sheet  trim  star drive (not sized in the sheet)  2, 2-1/2, 3-1/8\nBasic screw diameters (Grabber selection guide)  #8 / #10  —  —  —  #8 0.1640 in, #10 0.1900 in (basic screw diameter)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- SC Fastening (Simpson catalog): Simpson Strong-Tie Deck-Drive DSV wood screw #10 x 2 in. (DSVR2MB) and #8 x 1-1/4 in. (DSVT114R5LB): head diameter 0.330 in, T25 6-lobe, rimmed flat head with nibs, variable thread, high-low point — web — Distributor catalogue page; numbers only — https://catalog.scfastening.com/printitem/deck-drive-premium-fasteners/simpson-deck-drive-structural-wood-screws/dsvr2mb?plpver=10\n- Simpson Strong-Tie (DWP Wood SS data sheet, hosted on a Shopify CDN): Strong-Drive / Deck-Drive DWP Wood SS stainless screws: size, head diameter, drive, lengths for flat, trim and painted heads (#7 to #14) — web — Maker data sheet; numbers only — https://cdn.shopify.com/s/files/1/0398/5188/4705/files/DWP_WOOD_SS_Screw.pdf\n- GRK Fasteners (sell sheet via Fastenal): GRK selector guide: R4 #8 to #12, RSS, Fin/Trim and RT composite screws by size and length (no head dimensions in the sheet) — web — Maker sell sheet; numbers only — https://www.fastenal.com/content/public_notes/EB/GRK-sellsheet-2018.pdf\n- Grabber Construction Products: Self-drilling screw selection guide: basic screw diameter by normal size, 0 to 3/8 in (cross-check of #8 and #10 diameters) — web — Maker guide; numbers only — https://www.grabberpro.com/userfiles/documents/TechnicalDocuments/Manuals/Self-Drilling-Screw-Selection-Guide.pdf\n- Weinmann + Schanz (SPAX distributor): SPAX universal screw 4.0 mm thread diameter, 8.0 mm head diameter, T20; no pre-drill diameter given — web — Distributor page; numbers only — https://weinmann-schanz.de/de/en/Promotions/pid.1143.1159/agid.37023/ecm.ag/SPAX%C2%AE-universal-screw-thread-%C3%B8-d1-4-0-mm-head-%C3%B8-8-0-mm-standard-packaging.html\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=deck-screws-8-10-simpson-grk\n",
 "sources": [
  {
   "publisher": "SC Fastening (Simpson catalog)",
   "title": "Simpson Strong-Tie Deck-Drive DSV wood screw #10 x 2 in. (DSVR2MB) and #8 x 1-1/4 in. (DSVT114R5LB): head diameter 0.330 in, T25 6-lobe, rimmed flat head with nibs, variable thread, high-low point",
   "url": "https://catalog.scfastening.com/printitem/deck-drive-premium-fasteners/simpson-deck-drive-structural-wood-screws/dsvr2mb?plpver=10",
   "formats": [
    "web"
   ],
   "license": "Distributor catalogue page; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Simpson Strong-Tie (DWP Wood SS data sheet, hosted on a Shopify CDN)",
   "title": "Strong-Drive / Deck-Drive DWP Wood SS stainless screws: size, head diameter, drive, lengths for flat, trim and painted heads (#7 to #14)",
   "url": "https://cdn.shopify.com/s/files/1/0398/5188/4705/files/DWP_WOOD_SS_Screw.pdf",
   "formats": [
    "web"
   ],
   "license": "Maker data sheet; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "GRK Fasteners (sell sheet via Fastenal)",
   "title": "GRK selector guide: R4 #8 to #12, RSS, Fin/Trim and RT composite screws by size and length (no head dimensions in the sheet)",
   "url": "https://www.fastenal.com/content/public_notes/EB/GRK-sellsheet-2018.pdf",
   "formats": [
    "web"
   ],
   "license": "Maker sell sheet; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Grabber Construction Products",
   "title": "Self-drilling screw selection guide: basic screw diameter by normal size, 0 to 3/8 in (cross-check of #8 and #10 diameters)",
   "url": "https://www.grabberpro.com/userfiles/documents/TechnicalDocuments/Manuals/Self-Drilling-Screw-Selection-Guide.pdf",
   "formats": [
    "web"
   ],
   "license": "Maker guide; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Weinmann + Schanz (SPAX distributor)",
   "title": "SPAX universal screw 4.0 mm thread diameter, 8.0 mm head diameter, T20; no pre-drill diameter given",
   "url": "https://weinmann-schanz.de/de/en/Promotions/pid.1143.1159/agid.37023/ecm.ag/SPAX%C2%AE-universal-screw-thread-%C3%B8-d1-4-0-mm-head-%C3%B8-8-0-mm-standard-packaging.html",
   "formats": [
    "web"
   ],
   "license": "Distributor page; numbers only",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "torx-hexalobular-drive-sizes-iso-10664",
  "wood-screws-flat-head-inch",
  "chipboard-wood-screws-din-7505",
  "lag-screws-hex-inch",
  "plywood-and-drywall",
  "dimensional-lumber"
 ],
 "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 bit does a #10 deck screw use?",
   "a": "T25 six-lobe on Simpson Deck-Drive DSV and DWP #10 screws; #8 DWP screws use T20 (Simpson)."
  },
  {
   "q": "What is the head diameter of a #10 deck screw?",
   "a": "0.330 in on the Simpson DSV #10 × 2 in (T25) and 0.34 in on the flat-head DWP Wood SS #10."
  },
  {
   "q": "What is the diameter of a #8 and a #10 screw?",
   "a": "Basic screw diameter 0.1640 in for #8 and 0.1900 in for #10 (Grabber's table)."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/deck-screws-8-10-simpson-grk/index.md"
}