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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

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? · Standard part · 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

Also called: #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

Exact dimensions. True size, with no tolerance added.

sizes
18 in table

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.

Deck screws #8 and #10: head diameter (0.330 / 0.34 in), six-lobe… size chart

linesizehead diameter (in)head styledrivelengths (in)
Simpson Deck-Drive DSV (catalog item DSVR2MB, #10 x 2)#100.330rimmed flat head with nibsT25 six-lobe2 (item read); other lengths exist
Simpson Deck-Drive DSV (catalog item DSVT114R5LB, #8 x 1-1/4)#80.330rimmed flat head with nibsT25 six-lobe1-1/4 (item read); other lengths exist
Simpson Deck-Drive DWP Wood SS, 316 SS, flat#80.34flatT201-1/4, 1-5/8, 2, 2-1/2, 3
Simpson Deck-Drive DWP Wood SS, 316 SS, flat#100.34flatT252, 2-1/2, 3, 3-1/2, 4-1/2
Simpson Deck-Drive DWP Wood SS, 305 SS, flat#80.34flatT201-1/4, 1-5/8, 2, 2-1/2, 3
Simpson Deck-Drive DWP Wood SS, 305 SS, flat#100.34flatT251, 1-1/2, 2, 2-1/2, 3, 3-1/2
Simpson Deck-Drive DWP Wood SS, 305 SS, trim#70.23trimT151, 1-1/4, 1-5/8, 2, 2-1/4, 2-1/2, 3
Simpson Deck-Drive DWP Wood SS, 305 SS, trim#80.25trimT202-1/2, 3
Simpson Deck-Drive DWP Wood SS, 305 SS, trim#90.25trimT203-1/2, 4
Simpson Deck-Drive DWP Wood SS, 316 SS, trim#70.23trimT151-5/8, 2-1/4, 3
Simpson DWP Wood SS, painted heads, trim#70.23trim (316 SS)T152-1/4, 3
Simpson DWP Wood SS, painted heads, trim#100.34trim (305 SS)T252-1/2, 3
Simpson DWP Wood SS, painted heads, flat#100.34flat (305 SS)T252-1/2, 3
Simpson DWP Wood SS, painted heads, trim (Quik Drive)#80.26trim (305 SS)T20 (Quik Drive collated screws use BITTX25 per the sheet)2-1/2
GRK R4 multi-purpose (sell sheet)#8 / #9 / #10 / #12not 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 / #9not in the sheettrimstar drive (not sized in the sheet)#8 1-1/2 to 3-1/8; #9 4, 5
GRK RT composite Fin/Trim (sell sheet)#8not in the sheettrimstar 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)

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

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 pointwebDistributor catalogue page; numbers only
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)webMaker data sheet; numbers only
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)webMaker sell sheet; numbers only
Grabber Construction ProductsSelf-drilling screw selection guide: basic screw diameter by normal size, 0 to 3/8 in (cross-check of #8 and #10 diameters)webMaker guide; numbers only
Weinmann + Schanz (SPAX distributor)SPAX universal screw 4.0 mm thread diameter, 8.0 mm head diameter, T20; no pre-drill diameter givenwebDistributor page; numbers only

Xem scan

File coming

No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.

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Plain text: sheet.txt · JSON: /api/geometry?object=deck-screws-8-10-simpson-grk

Schematic, not to scale.

Fits with

length
Torx / hexalobular drive sizes T1–T100 (ISO 10664): A and B across lobes, gauge limits for A, B, Ri, Re and depth H, and the screw size each fits24 sizes★ sheet
Flat-head wood screws, inch #4–#14 (ASME B18.6.1): body and head diameter, pilot and clearance holes from three sources + envelope models, isometric render of a generated part
Flat-head wood screws, inch #4–#14 (ASME B18.6.1): body and head diameter, pilot and clearance holes from three sources + envelope models38.1×12.9×12.9 mm★ 6 files
Chipboard screws, DIN 7505 (3, 3.5, 4, 4.5, 5, 6 mm): pan, countersunk and oval-countersunk head dimensions, cross recess size + type-B envelope models, isometric render of a generated part
Chipboard screws, DIN 7505 (3, 3.5, 4, 4.5, 5, 6 mm): pan, countersunk and oval-countersunk head dimensions, cross recess size + type-B envelope models40.0×12.0×12.0 mm★ 6 files
Hex lag screws, 1/4 to 1/2 in (ASME B18.2.1): shank, head width and height, pilot holes + envelope models, isometric render of a generated part
Hex lag screws, 1/4 to 1/2 in (ASME B18.2.1): shank, head width and height, pilot holes + envelope models22.0×19.0×84.9 mm★ 5 files
Plywood and drywall sheets: 4 × 8 ft at actual thickness (3/4 in plywood = 23/32 in), isometric render of a generated part
Plywood and drywall sheets: 4 × 8 ft at actual thickness (3/4 in plywood = 23/32 in)9 sizes★ 13 files
Dimensional lumber: actual sizes of 1x2 to 6x6, 8 to 16 ft (2x4 = 1-1/2 × 3-1/2 in), isometric render of a generated part
Dimensional lumber: actual sizes of 1x2 to 6x6, 8 to 16 ft (2x4 = 1-1/2 × 3-1/2 in)17 sizes★ 72 files

Questions

What bit does a #10 deck screw use?

T25 six-lobe on Simpson Deck-Drive DSV and DWP #10 screws; #8 DWP screws use T20 (Simpson).

What is the head diameter of a #10 deck screw?

0.330 in on the Simpson DSV #10 × 2 in (T25) and 0.34 in on the flat-head DWP Wood SS #10.

What is the diameter of a #8 and a #10 screw?

Basic screw diameter 0.1640 in for #8 and 0.1900 in for #10 (Grabber's table).