--- title: "M8 Countersunk Socket Screws Dimensions" description: "M8 Countersunk Socket Screws: head diameter 17.92 mm, head height 4.96 mm, coarse thread pitch 1.25 mm. Tightening torque 24 Nm at class 8.8." url: https://engineeringhardware.com/guide/size/m8-countersunk-socket-screws/ source: Engineering Hardware & Fasteners --- # M8 Countersunk Socket Screws Dimensions Screws · ISO 10642 / DIN 7991 Controlling dimensions to ISO 10642 / DIN 7991, with clearance hole and tapping drill, spanner or drive size and tightening torque. M8 Countersunk Socket Screws dimensions to ISO 10642 / DIN 7991: head diameter 17.92 mm, head height 4.96 mm, coarse thread pitch 1.25 mm, clearance hole (ISO 273 medium) 9 mm. Tighten to approximately 24 Nm at property class 8.8 in a dry, as-supplied condition. - **Head diameter:** 17.92 mm - **Head height:** 4.96 mm - **Coarse thread pitch:** 1.25 mm - **Clearance hole (ISO 273 medium):** 9 mm - **Tightening torque (class 8.8):** 24 Nm Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering. ![M8 Countersunk Socket Screws Dimensions reference image](https://engineeringhardware.com/wp-content/uploads/2026/06/Countersunk-Socket-Screws-—-ISO-10642-／-DIN-7991-Detail.webp) Dimensional and assembly data for M8 Countersunk Socket Screws to ISO 10642 / DIN 7991. Includes head size and width across flats, clearance-hole and tapping-drill diameters, tightening torque per property class, and the sizes to step up or down to when the joint requires it. ## M8 Dimensional Row (ISO 10642 / DIN 7991) | Size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Hex key s (mm) | Countersink angle (deg) | Reference standard | | --- | --- | --- | --- | --- | --- | --- | | M8 | 1.25 | 17.92 | 4.96 | 5.0 | 90 | ISO 10642 / DIN 7991 | ## Spanner & Drive for M8 Countersunk Socket Screws The hex socket for M8 Countersunk Socket Screws is shown in the spec table — use the matching Allen / hex key (an ISO 2936 hex key set covers the full range). A T-handle key gives the most feel when you are judging preload by hand; anything repeated across a batch wants a torque-controlled driver instead. ## Hole Sizes for M8 | Coarse-thread pitch (ISO 724) | 1.25 mm | | --- | --- | | Through-hole / clearance (ISO 273 medium) | 9 mm | | Tapping drill, coarse thread | 6.75 mm | ## Tightening Torque for M8 | Class 8.8 (dry, ~µ 0.125) | ≈ 24 Nm | | --- | --- | | Class 10.9 (dry, ~µ 0.125) | ≈ 36 Nm | | Class 12.9 (dry, ~µ 0.125) | ≈ 42 Nm | Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class. ## Proof Load & Strength for M8 | Tensile stress area As (ISO 724) | 36.6 mm² | | --- | --- | | Proof load, class 8.8 | 21 kN | | Proof load, class 10.9 | 30 kN | | Proof load, class 12.9 | 36 kN | | Min. ultimate tensile load, class 8.8 | 29 kN | Proof load = tensile stress area × the proof stress Sp of the class, per ISO 898-1 — Sp is a lower figure than the yield stress Rp0.2 and the two are not interchangeable. The stress area is computed from this size's own diameter and pitch, so a fine-pitch designation gives the fine-pitch figure. Design the joint so the working preload stays below the proof load of the class selected. ## Installation Tips for M8 Countersunk Socket Screws - Use a quality Allen key fully seated in the socket — partial engagement is the most common cause of stripped sockets at this size. - For countersunk and button-head variants, chamfer the through-hole to seat the head flush without preloading the head/shank fillet. ## When to Step Up or Down from M8 When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin. Custom manufacturing · Made to drawing ## Need countersunk socket screws in a size this table does not list? This page covers M8 countersunk socket screws. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or warm forging. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom screw manufacturing](https://engineeringhardware.com/custom/screws/)[Send a drawing](https://engineeringhardware.com/custom/screws/#rfq) ## Technical Drawing Dimensioned line drawing of M8 Countersunk Socket Screws to ISO 10642 / DIN 7991. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Pitch (mm):** 1.25 - **Head diameter dk (mm):** 17.92 - **Head height k (mm):** 4.96 - **Hex key s (mm):** 5.0 - **Countersink angle (deg):** 90 ## Dimensions & Specifications (ISO 10642 / DIN 7991) | Size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Hex key s (mm) | Countersink angle (deg) | Reference standard | | --- | --- | --- | --- | --- | --- | --- | | M3 | 0.5 | 6.72 | 1.86 | 2.0 | 90 | ISO 10642 / DIN 7991 | | M4 | 0.7 | 8.96 | 2.48 | 2.5 | 90 | ISO 10642 / DIN 7991 | | M5 | 0.8 | 11.2 | 3.1 | 3.0 | 90 | ISO 10642 / DIN 7991 | | M6 | 1.0 | 13.44 | 3.72 | 4.0 | 90 | ISO 10642 / DIN 7991 | | M8 | 1.25 | 17.92 | 4.96 | 5.0 | 90 | ISO 10642 / DIN 7991 | | M10 | 1.5 | 22.4 | 6.2 | 6.0 | 90 | ISO 10642 / DIN 7991 | | M12 | 1.75 | 26.88 | 7.44 | 8.0 | 90 | ISO 10642 / DIN 7991 | | M14 | 2.0 | 30.0 | 8.4 | 10.0 | 90 | ISO 10642 / DIN 7991 | | M16 | 2.0 | 33.6 | 9.3 | 10.0 | 90 | ISO 10642 / DIN 7991 | | M20 | 2.5 | 40.32 | 11.2 | 12.0 | 90 | ISO 10642 / DIN 7991 | | M24 | 3.0 | 47.04 | 13.0 | 14.0 | 90 | ISO 10642 / DIN 7991 | ## Materials & Grades Select a material class to see the grades we supply it in. Each designation is listed with its ISO/EN, AISI/SAE, JIS and GB equivalents. Stainless Steel38 Carbon Steel66 Alloy Steel41 Bearing Steel5 Spring Steel25 Aluminum and Aluminum Alloys21 Brass17 Bronze11 Copper8 Titanium and Titanium Alloys18 Nickel and Nickel Alloys22 Iron-Nickel and High-Temperature Alloys10 Tool Steel and Specialty Hardened Steel9 Structural and Construction Steel9 ### Stainless Steel #### Austenitic Stainless Steel - A1 AISI 303 · SAE 303 · SUS303 · EN 1.4305 · X8CrNiS18-9 - A2 AISI 304 · SAE 304 · SUS304 · EN 1.4301 · X5CrNi18-10 · 06Cr19Ni10 - 304L AISI 304L · SUS304L · EN 1.4307 · X2CrNi18-9 · 022Cr19Ni10 - 302 AISI 302 · SUS302 · EN 1.4310 - 305 AISI 305 · SUS305 · EN 1.4303 - A4 AISI 316 · SAE 316 · SUS316 · EN 1.4401 · X5CrNiMo17-12-2 · 06Cr17Ni12Mo2 - 316L AISI 316L · SUS316L · EN 1.4404 · X2CrNiMo17-12-2 · 022Cr17Ni12Mo2 - 321 AISI 321 · SUS321 · EN 1.4541 · X6CrNiTi18-10 - 310 / 310S AISI 310 · AISI 310S · SUS310S · EN 1.4845 - 302HQ AISI 302HQ - A3 - A5 - 347 AISI 347 · SUS347 · EN 1.4550 · X6CrNiNb18-10 - 309 / 309S AISI 309 · AISI 309S · SUS309S #### Martensitic Stainless Steel - AISI 410 SUS410 · EN 1.4006 · X12Cr13 · 12Cr13 - AISI 420 SUS420J1 · SUS420J2 · EN 1.4021 · EN 1.4028 · 20Cr13 · 30Cr13 - AISI 431 SUS431 · EN 1.4057 · X17CrNi16-2 - C1 - C3 - C4 - AISI 440A - AISI 440B - AISI 440C SUS440C · EN 1.4125 #### Ferritic Stainless Steel - AISI 430 SUS430 · EN 1.4016 · X6Cr17 · 10Cr17 - F1 - AISI 434 - AISI 444 #### Precipitation-Hardening Stainless Steel - 17-4 PH AISI 630 · UNS S17400 · SUS630 · EN 1.4542 · X5CrNiCuNb16-4 - 15-5 PH UNS S15500 - 17-7 PH UNS S17700 #### Duplex and Super Duplex Stainless Steel - Duplex 2205 UNS S31803 · UNS S32205 · EN 1.4462 - Super Duplex 2507 UNS S32750 · EN 1.4410 - D2 - D4 - D6 - D8 - Lean Duplex 2101 UNS S32101 - Super Duplex S32760 UNS S32760 · EN 1.4501 ### Carbon Steel #### Low-Carbon Steel - SAE 1006 - SAE 1008 - SAE 1010 - SAE 1018 - SAE 1020 - Q195 - Q235 - SAE 1012 - SAE 1015 - Q215 - ML08 - ML08Al - ML10 - ML15 - ML20 - SWRCH6A - SWRCH8A - SWRCH10A - SWRCH12A - SWRCH15A - SWRCH18A #### Medium-Carbon Steel - SAE 1035 - SAE 1045 - S45C - C45 - SAE 1030 - SAE 1040 - SAE 1050 - 30 - 35 - 40 - 45 - 50 - S35C - S40C - S50C - C35 - C40 #### High-Carbon Steel - SAE 1060 - SAE 1070 - 65Mn - SAE 1065 - SAE 1075 - SAE 1080 - SAE 1085 - SAE 1090 - SAE 1095 - 60 - 65 - 70 - 75 - 80 - 85 #### Cold-Heading Steel - SWRCH22A - 10B21 - SWRCH22K - SWRCH25K - SWRCH30K - SWRCH35K - SWRCH40K - ML20Mn - ML25 - ML30 - ML35 - ML40 - 15B25 ### Alloy Steel #### Chromium Steel - 40Cr - 45Cr - AISI 5140 - SAE 5140 - AISI 5120 - SAE 5120 - SCr420 - SCr440 #### Chromium-Molybdenum Steel - 35CrMo - 42CrMo - AISI 4140 - SCM435 - SCM440 - 42CrMo4 - 30CrMo - AISI 4130 - SAE 4130 - SAE 4140 - AISI 4142 - AISI 4145 - SCM415 - SCM420 - SCM445 - EN 1.7220 - EN 1.7225 - 25CrMo4 - 34CrMo4 #### Nickel-Chromium-Molybdenum Steel - AISI 4340 - SAE 4340 - 40CrNiMo - SNCM439 - EN 1.6511 - 36CrNiMo4 #### Boron Alloy Steel - 10B22 - 10B21 - 15B21 - 15B25 - 20MnTiB - 20Mn2B - 35VB - 40MnB ### Bearing Steel #### Bearing Steel - GCr15 - AISI 52100 SAE 52100 · UNS G52986 - SUJ2 - 100Cr6 EN 1.3505 - GCr15SiMn ### Spring Steel #### Carbon Spring Steel - SAE 1065 - SAE 1070 - SAE 1075 - SAE 1080 - SAE 1095 - 65 - 70 - 75 - 80 - 65Mn #### Silicon-Manganese Spring Steel - 60Si2Mn - 60Si2MnA - SUP6 - SUP7 #### Chromium-Vanadium Spring Steel - 50CrVA - SAE 6150 - AISI 6150 - SUP10 #### Stainless Spring Steel - AISI 301 - SUS301 - EN 1.4310 - AISI 302 - AISI 304 - AISI 316 - 17-7 PH ### Aluminum and Aluminum Alloys #### Commercially Pure Aluminum - 1050 - 1060 - 1070 - 1100 #### 2xxx Series Aluminum - 2024 - 2011 - 2014 - 2017 #### 5xxx Series Aluminum - 5052 - 5083 - 5754 #### 6xxx Series Aluminum - 6061 - 6061-T6 - 6063 - 6082 - 6082-T6 #### 7xxx Series Aluminum - 7075 - 7075-T6 - 7005 - 7050 - 7075-T73 ### Brass #### Free-Cutting Brass - C36000 - H62 - HPb59-1 - C3601 - C3602 - C3604 - CuZn36Pb3 - CuZn39Pb3 - EN CW614N - EN CW617N - H65 #### Lead-Free Brass - C69300 - C27450 - CW510L - CW511L #### Naval Brass - C46400 - CuZn39Sn1 ### Bronze #### Silicon Bronze - C65500 - C65100 - C65600 #### Phosphor Bronze - C51000 - C52100 - CuSn6 - CuSn8 #### Aluminum Bronze - C95400 - C95500 - C63000 - CuAl10Ni5Fe4 ### Copper #### Copper - C11000 - T2 - C10100 - C10200 - C12200 - T1 - TU1 - TU2 ### Titanium and Titanium Alloys #### Commercially Pure Titanium - Grade 2 - Grade 1 - Grade 3 - Grade 4 - TA1 - TA2 - TA3 #### Alpha-Beta Titanium Alloys - Grade 5 - Ti-6Al-4V - TC4 - UNS R56400 #### Low-Interstitial Grade - Grade 23 - Ti-6Al-4V ELI - UNS R56407 #### Other Titanium Fastener Alloys - Ti-6Al-6V-2Sn - Ti-6Al-2Sn-4Zr-2Mo - Beta-C titanium - Ti-10V-2Fe-3Al ### Nickel and Nickel Alloys #### Commercially Pure Nickel - Nickel 200 - UNS N02200 - Nickel 201 - UNS N02201 #### Inconel Alloys - Inconel 625 UNS N06625 - Inconel 718 UNS N07718 - Inconel 600 UNS N06600 - Inconel 601 UNS N06601 - Inconel 686 UNS N06686 - Inconel X-750 UNS N07750 #### Monel Alloys - Monel 400 UNS N04400 - Monel K-500 UNS N05500 #### Hastelloy Alloys - Hastelloy C-276 UNS N10276 - Hastelloy C-22 UNS N06022 - Hastelloy B-2 UNS N10665 - Hastelloy B-3 UNS N10675 - Hastelloy X UNS N06002 #### Other Nickel Alloys - Alloy 20 UNS N08020 - Alloy 625 - Alloy 718 - Alloy 825 UNS N08825 - Alloy 925 UNS N09925 ### Iron-Nickel and High-Temperature Alloys #### A286 - A-286 - UNS S66286 - EN 1.4980 #### Invar - Invar 36 - Alloy 36 - UNS K93600 - FeNi36 #### Alloy 42 - Alloy 42 - UNS K94100 - FeNi42 ### Tool Steel and Specialty Hardened Steel #### Tool Steel and Specialty Hardened Steel - AISI D2 - AISI H13 - SKD11 - Cr12MoV - AISI O1 - AISI A2 - AISI S7 - SKD61 - 9CrSi ### Structural and Construction Steel #### Structural and Construction Steel - ASTM A36 - Q235B - Q355B - S355JR - Q235C - Q355C - S235JR - S275JR - S355J2 ## Applications & Industries for M8 Countersunk Socket Screws What Countersunk Socket Screws are specified for, industry by industry. Stocked from M3 to M24. ### Industries that specify Countersunk Socket Screws - **Machine building & OEM:** The default fastener on production equipment: covers, brackets, motor mounts and sub-assemblies tightened to a specified torque. - **Automotive & transport:** Chassis, driveline and body fixings that see vibration and are assembled to a controlled preload. - **Steel fabrication:** Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site. - **Energy & infrastructure:** Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints. - **Maintenance & MRO:** Stocked replacements matched to an existing property class, thread and finish. - **Food, pharma & cleanroom:** Stainless assemblies that are washed down, where the finish matters as much as the strength. ### Typical applications - assemblies that are dismantled for service and re-torqued - joints where the property class is stated on the drawing - clamping two machined faces to a calculated preload - bolting brackets, motors and gearboxes to a frame ### Service conditions to specify against - **Marine and coastal:** Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit. - **High load:** Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel. - **Torque and preload:** The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together. ### Where to use something else - Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material. [Full application guide: where Countersunk Socket Screws are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/countersunk-socket-screws/) Inside the plant ## Manufactured in our own plant This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided. 1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift. 2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g. 3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1. 4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227. ## Frequently Asked Questions ### What is the coarse-thread pitch of M8 for Countersunk Socket Screws? For M8 the standard coarse pitch is 1.25 mm — this is the value used for Countersunk Socket Screws. ### What torque do M8 class 8.8 Countersunk Socket Screws take? A dry M8 class 8.8 joint takes about 24 Nm (≈ 36 Nm for 10.9, ≈ 42 Nm for 12.9). Confirm against your joint design; lubrication reduces these values. ### What clearance and tapping drill suit M8? Use a 9 mm clearance hole (ISO 273 medium) for through-fixing, or a 6.75 mm tapping drill for a coarse M8 thread. ### Which Allen key fits M8 Countersunk Socket Screws? The hex-socket size for each row of Countersunk Socket Screws is shown in the spec table — use the matching Allen / hex key. An ISO 2936 set covers every size on this page. ### How do I request a quotation? Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day. ## Related Pages [View the full Countersunk Socket Screws page](https://engineeringhardware.com/fastener/countersunk-socket-screws/) ### More Countersunk Socket Screws Guides