{ "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": "lag-screws-hex-inch-5-8-to-1", "name": "Hex lag screws 5/8, 3/4, 7/8 and 1 in (ASME B18.2.1): head width and height, shank, pilot holes + envelope models", "kind": "standard", "category": "Hardware", "group": "Fasteners", "year": null, "question": "What size is the head of a 3/4 lag screw, and what pilot hole does a 5/8 lag bolt need?", "tags": [ "lag screw", "lag bolt", "hex lag screw", "pilot hole", "asme b18.2.1", "5/8 lag", "3/4 lag", "7/8 lag", "1 inch lag", "fastener", "wood" ], "aliases": [ "5/8 lag screw head size", "3/4 lag screw wrench size", "1/2 inch lag bolt head", "5/8 lag screw pilot hole", "3/4 lag bolt pilot hole hardwood", "7/8 lag screw head width", "1 inch lag bolt dimensions", "lag screw head height 5/8", "lag bolt threads per inch 3/4", "large lag screw dimensions chart", "b18.2.1 lag screw 5/8 to 1", "lag bolt socket size 3/4" ], "overall_mm": { "length": 44, "width": 38.1, "height": 118.7 }, "official_cad": false, "xem_status": "free-files", "les": false, "free_files": 4, "url": "https://xemstudio.com/objects/lag-screws-hex-inch-5-8-to-1/", "sheet_txt": "https://xemstudio.com/objects/lag-screws-hex-inch-5-8-to-1/sheet.txt", "sheet": { "basis": "AFT Fasteners' ASME B18.2.1-1996 table (5/8, 3/4, 7/8) with Engineers Edge (5/8 to 1) and Fastenermart (head and pilot holes, 5/8 and 3/4) as cross-checks; four envelope models as files", "overall_mm": { "length": 44, "width": 38.1, "height": 118.7 }, "notes": [ "Inches. Sizes 5/8, 3/4, 7/8 and 1 in extend lag-screws-hex-inch (1/4 to 1/2 in). AFT's table (it cites ASME B18.2.1-1996) stops at 7/8; the 1 in row is from Engineers Edge alone, so its basic width across flats (1-1/2) and head height (43/64) have no second source here, and its across-corners and shoulder length are left blank. AFT's flattened table was read by assigning columns from the layout (E, F, G, H, S), so check the standard if a figure matters.", "Engineers Edge agrees with AFT on E, F and H for 5/8, 3/4 and 7/8. One misprint: its 7/8 row prints a basic F of '15/16' beside a max / min of 1.312 / 1.269, which is 1-5/16 (AFT prints 1-5/16); 1-5/16 is used. Fastenermart agrees on head width and height for 5/8 and 3/4 (15/16 and 27/64; 1-1/8 and 1/2).", "Thread length is a rule, not a column: AFT gives a minimum of half the screw length plus 0.50 in, up to 5.00 in; short screws are threaded close to the head. Pilot holes are not part of B18.2.1: Fastenermart prints a shank hole equal to the nominal size and threaded-portion pilots by wood group (5/8: 5/16 softwood III and IV, 13/32 medium II, 29/64 hardwood I; 3/4: 13/32, 1/2, 9/16). The page has no pilot holes for 7/8 or 1 in, so none are shown. Treat pilots as a guide and follow the screw maker or the project engineer.", "Files: hexagon at the basic width across flats and the basic height (corners are F / cos 30°, which AFT's G max matches, e.g. 1.083 in for 5/8) on a plain cylinder at the nominal diameter; no thread, chamfer, washer face or point. The 4 in length under the head is an example chosen by Xem, not a published length. The 1 in file uses the single-source head size.", "McMaster-Carr sells lag screws with per-part STEP; its category is linked, not copied. Smaller sizes: lag-screws-hex-inch. Wood screws: wood-screws-flat-head-inch." ], "table": { "columns": [ "size (in)", "TPI", "shank E max / min (in)", "across flats F, basic", "F max / min (AFT)", "F (Engineers Edge)", "across corners G max / min (AFT)", "head height H, basic", "H max / min", "shoulder S min (AFT)", "shank hole (Fastenermart)", "pilot, softwood III & IV", "pilot, medium II", "pilot, hardwood I" ], "rows": [ [ "5/8", "5", ".642 / .605", "15/16", ".938 / .906", "15/16 (.938 / .906)", "1.083 / 1.033", "27/64", ".444 / .378", ".312", "5/8", "5/16", "13/32", "29/64" ], [ "3/4", "4-1/2", ".768 / .729", "1-1/8", "1.125 / 1.088", "1-1/8 (1.125 / 1.088)", "1.299 / 1.240", "1/2", ".524 / .455", ".375", "3/4", "13/32", "1/2", "9/16" ], [ "7/8", "4", ".895 / .852", "1-5/16", "1.312 / 1.269", "'15/16' printed; max / min 1.312 / 1.269", "1.516 / 1.447", "37/64", ".604 / .531", ".375", "—", "—", "—", "—" ], [ "1", "3-1/2", "1.022 / .976", "1-1/2 (Engineers Edge only)", "1.500 / 1.450", "1-1/2 (1.500 / 1.450)", "—", "43/64 (Engineers Edge only)", ".700 / .591", "—", "—", "—", "—", "—" ] ] } }, "sheet_text": "Hex lag screws 5/8, 3/4, 7/8 and 1 in (ASME B18.2.1): head width and height, shank, pilot holes + envelope models — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/lag-screws-hex-inch-5-8-to-1/ (sheet CC BY 4.0)\nBasis: AFT Fasteners' ASME B18.2.1-1996 table (5/8, 3/4, 7/8) with Engineers Edge (5/8 to 1) and Fastenermart (head and pilot holes, 5/8 and 3/4) as cross-checks; four envelope models as files\nCatalog version: 2026-10-20\n\nOverall (mm): length 44.0, width 38.1, height 118.7\n- Inches. Sizes 5/8, 3/4, 7/8 and 1 in extend lag-screws-hex-inch (1/4 to 1/2 in). AFT's table (it cites ASME B18.2.1-1996) stops at 7/8; the 1 in row is from Engineers Edge alone, so its basic width across flats (1-1/2) and head height (43/64) have no second source here, and its across-corners and shoulder length are left blank. AFT's flattened table was read by assigning columns from the layout (E, F, G, H, S), so check the standard if a figure matters.\n- Engineers Edge agrees with AFT on E, F and H for 5/8, 3/4 and 7/8. One misprint: its 7/8 row prints a basic F of '15/16' beside a max / min of 1.312 / 1.269, which is 1-5/16 (AFT prints 1-5/16); 1-5/16 is used. Fastenermart agrees on head width and height for 5/8 and 3/4 (15/16 and 27/64; 1-1/8 and 1/2).\n- Thread length is a rule, not a column: AFT gives a minimum of half the screw length plus 0.50 in, up to 5.00 in; short screws are threaded close to the head. Pilot holes are not part of B18.2.1: Fastenermart prints a shank hole equal to the nominal size and threaded-portion pilots by wood group (5/8: 5/16 softwood III and IV, 13/32 medium II, 29/64 hardwood I; 3/4: 13/32, 1/2, 9/16). The page has no pilot holes for 7/8 or 1 in, so none are shown. Treat pilots as a guide and follow the screw maker or the project engineer.\n- Files: hexagon at the basic width across flats and the basic height (corners are F / cos 30°, which AFT's G max matches, e.g. 1.083 in for 5/8) on a plain cylinder at the nominal diameter; no thread, chamfer, washer face or point. The 4 in length under the head is an example chosen by Xem, not a published length. The 1 in file uses the single-source head size.\n- McMaster-Carr sells lag screws with per-part STEP; its category is linked, not copied. Smaller sizes: lag-screws-hex-inch. Wood screws: wood-screws-flat-head-inch.\n\nsize (in) TPI shank E max / min (in) across flats F, basic F max / min (AFT) F (Engineers Edge) across corners G max / min (AFT) head height H, basic H max / min shoulder S min (AFT) shank hole (Fastenermart) pilot, softwood III & IV pilot, medium II pilot, hardwood I\n5/8 5 .642 / .605 15/16 .938 / .906 15/16 (.938 / .906) 1.083 / 1.033 27/64 .444 / .378 .312 5/8 5/16 13/32 29/64\n3/4 4-1/2 .768 / .729 1-1/8 1.125 / 1.088 1-1/8 (1.125 / 1.088) 1.299 / 1.240 1/2 .524 / .455 .375 3/4 13/32 1/2 9/16\n7/8 4 .895 / .852 1-5/16 1.312 / 1.269 '15/16' printed; max / min 1.312 / 1.269 1.516 / 1.447 37/64 .604 / .531 .375 — — — —\n1 3-1/2 1.022 / .976 1-1/2 (Engineers Edge only) 1.500 / 1.450 1-1/2 (1.500 / 1.450) — 43/64 (Engineers Edge only) .700 / .591 — — — — —\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- AFT Fasteners: Lag screws dimensions and mechanical properties (ASME B18.2.1-1996): E shank, F width across flats, G across corners, H head height, S shoulder length, thread-length rule — web — Publisher's page; dimensions are facts — https://www.aftfasteners.com/lag-screws-dimensions-and-mechanical-properties/\n- Engineers Edge: Standard hex lag screws: shank diameter E, width across flats F, head height H, threads per inch, 5/8 to 1 in — web — Publisher's page; dimensions are facts — https://ns1.engineersedge.com/hardware/standard_hex_lag_screws_16077.htm\n- Fastenermart: Lag screws: pilot hole sizes by wood group and head dimensions (5/8 and 3/4 in rows) — web — Publisher's page; dimensions are facts — https://fastenermart.com/lag-screws.html\n- McMaster-Carr: Hex head lag screws (McMaster files them as hex head 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/stainless-steel-hex-head-lag-screws\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 4 parts): https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/index.json\nAPI: https://xemstudio.com/api/geometry?object=lag-screws-hex-inch-5-8-to-1\n", "sources": [ { "publisher": "AFT Fasteners", "title": "Lag screws dimensions and mechanical properties (ASME B18.2.1-1996): E shank, F width across flats, G across corners, H head height, S shoulder length, thread-length rule", "url": "https://www.aftfasteners.com/lag-screws-dimensions-and-mechanical-properties/", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "Engineers Edge", "title": "Standard hex lag screws: shank diameter E, width across flats F, head height H, threads per inch, 5/8 to 1 in", "url": "https://ns1.engineersedge.com/hardware/standard_hex_lag_screws_16077.htm", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "Fastenermart", "title": "Lag screws: pilot hole sizes by wood group and head dimensions (5/8 and 3/4 in rows)", "url": "https://fastenermart.com/lag-screws.html", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "McMaster-Carr", "title": "Hex head lag screws (McMaster files them as hex head wood screws) (free STEP/IGES per part, for your own design use; no redistribution)", "url": "https://www.mcmaster.com/stainless-steel-hex-head-lag-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", "wood-screws-flat-head-inch", "hex-bolts-inch", "hex-nuts-inch", "socket-head-cap-screws-inch", "flat-washers-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": [ { "feature": "shank (thread drawn as plain cylinder)", "exact": "Ø15.875 (5/8), 19.05 (3/4), 22.225 (7/8), 25.4 (1) mm", "mates": "unthreaded clearance hole in the part being clamped: shank hole = nominal size (Fastenermart, 5/8 and 3/4)", "fit": "slide", "files": "lag-screw-" }, { "feature": "pilot hole in the receiving timber (5/8, 3/4 only)", "exact": "5/8: 5/16 soft, 13/32 medium, 29/64 hard; 3/4: 13/32, 1/2, 9/16 in (Fastenermart)", "mates": "threaded portion of the lag screw", "fit": "designed", "files": "lag-screw-" }, { "feature": "hex head", "exact": "across flats 15/16, 1-1/8, 1-5/16, 1-1/2 in (basic)", "mates": "socket / wrench or recess that captures the head: width = F", "fit": "slide", "files": "lag-screw-" } ], "fit_classes": { "press": "stays put: pin, tube, bearing or magnet held by interference. ISO 286 equivalent: H7/p6 (locational interference) or tighter.", "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. ISO 286 equivalent: H7/g6 or H7/h6.", "run": "turns or slides in use: pin in a link, rod through a guide. ISO 286 equivalent: H8/f7 (close running).", "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. ISO 286 equivalent: H9/d9 (free running) or looser.", "clamp": "split part that closes on the mating part with screws: make it at size.", "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change." }, "faq": [ { "q": "What wrench size is a 3/4 lag screw?", "a": "1-1/8 in across flats (basic) in AFT's B18.2.1 table, Engineers Edge and Fastenermart; head height 1/2 in." }, { "q": "What pilot hole for a 5/8 lag screw?", "a": "Fastenermart: 5/16 in softwood (groups III and IV), 13/32 medium wood, 29/64 hardwood; the shank hole is 5/8 in." }, { "q": "How big is the head of a 1 in lag bolt?", "a": "Engineers Edge prints 1-1/2 in across flats and 43/64 in basic head height (max 1.500 / 1.450 and .700 / .591); no second source was found for this size." } ], "files_license": null, "offers": [ { "file": "lag-screw-5-8-hex-4in-envelope", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-5-8-hex-4in-envelope.step", "stl": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-5-8-hex-4in-envelope.stl", "note": "5/8 hex lag screw envelope: hex head 0.9375 in across flats (basic) × 0.4219 in high (basic) on a plain Ø15.88 mm (5/8 in nominal) shank, example length 4 in (101.6 mm) under the head (Xem's choice); no thread, chamfer, washer face or point" }, { "file": "lag-screw-3-4-hex-4in-envelope", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-3-4-hex-4in-envelope.step", "stl": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-3-4-hex-4in-envelope.stl", "note": "3/4 hex lag screw envelope: hex head 1.125 in across flats (basic) × 0.5 in high (basic) on a plain Ø19.05 mm (3/4 in nominal) shank, example length 4 in (101.6 mm) under the head (Xem's choice); no thread, chamfer, washer face or point" }, { "file": "lag-screw-7-8-hex-4in-envelope", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-7-8-hex-4in-envelope.step", "stl": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-7-8-hex-4in-envelope.stl", "note": "7/8 hex lag screw envelope: hex head 1.3125 in across flats (basic) × 0.5781 in high (basic) on a plain Ø22.22 mm (7/8 in nominal) shank, example length 4 in (101.6 mm) under the head (Xem's choice); no thread, chamfer, washer face or point" }, { "file": "lag-screw-1-hex-4in-envelope", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-1-hex-4in-envelope.step", "stl": "https://xemstudio.com/files/hardware/lag-screws-hex-inch-5-8-to-1/lag-screw-1-hex-4in-envelope.stl", "note": "1 hex lag screw envelope: hex head 1.5 in across flats (basic) × 0.6719 in high (basic) on a plain Ø25.40 mm (1 in nominal) shank, example length 4 in (101.6 mm) under the head (Xem's choice); no thread, chamfer, washer face or point" } ], "markdown": "https://xemstudio.com/objects/lag-screws-hex-inch-5-8-to-1/index.md" }