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 Source: Xem Studio, https://xemstudio.com/objects/deck-screws-8-10-simpson-grk/ (sheet CC BY 4.0) 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 Catalog version: 2026-10-20 Sizes: see table below - 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. line size head diameter (in) head style drive lengths (in) 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) Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - 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 - 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 - 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 - 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 - 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 No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned. API: https://xemstudio.com/api/geometry?object=deck-screws-8-10-simpson-grk