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Sourcing these sizes? DIN 7991 countersunk socket screws Socket head screw supplier
DIN 7991 countersunk screw dimensions (mm)
Head diameter dk and head height k are maximum values. Socket s is the hex key size and t the maximum socket depth. The head angle is 90° up to M20; M22 and M24 use a 60° head. Values are from the published DIN 7991 table.
| Size | Pitch P | Head dia. dk max | dk min | Head height k max | Hex key s | Socket depth t max | Head angle | Inquiry |
|---|---|---|---|---|---|---|---|---|
| M3 | 0.5 | 6 | 5.7 | 1.7 | 2 | 1.2 | 90° | Quote this size |
| M4 | 0.7 | 8 | 7.64 | 2.3 | 2.5 | 1.8 | 90° | Quote this size |
| M5 | 0.8 | 10 | 9.64 | 2.8 | 3 | 2.3 | 90° | Quote this size |
| M6 | 1.0 | 12 | 11.57 | 3.3 | 4 | 2.5 | 90° | Quote this size |
| M8 | 1.25 | 16 | 15.57 | 4.4 | 5 | 3.5 | 90° | Quote this size |
| M10 | 1.5 | 20 | 19.48 | 5.5 | 6 | 4.4 | 90° | Quote this size |
| M12 | 1.75 | 24 | 23.48 | 6.5 | 8 | 4.6 | 90° | Quote this size |
| M14 | 2.0 | 27 | 26.48 | 7 | 10 | 4.8 | 90° | Quote this size |
| M16 | 2.0 | 30 | 29.48 | 7.5 | 10 | 5.3 | 90° | Quote this size |
| M18 | 2.5 | 33 | 32.38 | 8 | 12 | 5.5 | 90° | Quote this size |
| M20 | 2.5 | 36 | 35.38 | 8.5 | 12 | 5.9 | 90° | Quote this size |
| M22 | 2.5 | 36 | 35.38 | 13.1 | 14 | 8.8 | 60° | Quote this size |
| M24 | 3.0 | 39 | 38.38 | 14 | 14 | 10.3 | 60° | Quote this size |
Thread length b (mm)
Longer DIN 7991 screws are partly threaded. The reference thread length b follows the same pattern as DIN 931: 2d + 6 for lengths up to 125 mm, 2d + 12 from 125 to 200 mm, and 2d + 25 above 200 mm. Shorter screws are threaded close to the head.
| Size | b for L ≤ 125 | b for 125 < L ≤ 200 | b for L > 200 | Inquiry |
|---|---|---|---|---|
| M6 | 18 | 24 | — | Quote this size |
| M8 | 22 | 28 | — | Quote this size |
| M10 | 26 | 32 | 45 | Quote this size |
| M12 | 30 | 36 | 49 | Quote this size |
| M16 | 38 | 44 | 57 | Quote this size |
| M20 | 46 | 52 | 65 | Quote this size |
| M24 | 54 | 60 | 73 | Quote this size |
DIN 7991 vs ISO 10642: head sizes compared
ISO 10642 replaced DIN 7991, but the heads were redesigned. The ISO head is larger and taller in every size. A screw made to ISO 10642 may stand proud of a countersink cut for DIN 7991, and a DIN screw in an ISO countersink sits below the surface. ISO 10642 also drops M18, M22 and M24, removes stainless steel from the standard, and covers classes 8.8, 10.9 and 12.9 with reduced-loadability marking (for example 08.8 or 010.9).
| Size | DIN 7991 dk max | ISO 10642 dk max | DIN 7991 k max | ISO 10642 k max | Hex key (both) | Inquiry |
|---|---|---|---|---|---|---|
| M3 | 6 | 6.72 | 1.7 | 1.86 | 2 | Quote this size |
| M4 | 8 | 8.96 | 2.3 | 2.48 | 2.5 | Quote this size |
| M5 | 10 | 11.20 | 2.8 | 3.1 | 3 | Quote this size |
| M6 | 12 | 13.44 | 3.3 | 3.72 | 4 | Quote this size |
| M8 | 16 | 17.92 | 4.4 | 4.96 | 5 | Quote this size |
| M10 | 20 | 22.4 | 5.5 | 6.2 | 6 | Quote this size |
| M12 | 24 | 26.88 | 6.5 | 7.44 | 8 | Quote this size |
| M16 | 30 | 33.6 | 7.5 | 8.8 | 10 | Quote this size |
| M20 | 36 | 40.32 | 8.5 | 10.16 | 12 | Quote this size |
Need these DIN 7991 / ISO 10642 sizes? Request a quote
- ISO 10642 dk max is the theoretical sharp-edge diameter; the actual head is smaller (for M8, dk min is 15.24 mm).
- If you are replacing screws in existing machined parts, order the same standard the countersinks were cut for.
- For new designs, state one standard on the drawing and cut the countersink to it.
Approximate weight per 1000 pcs (kg)
Weights are for plain steel DIN 7991 screws (density 7.85 kg/dm³), from the published DIN 7991 mass table.
| Size × length | kg / 1000 | Size × length | kg / 1000 | Inquiry |
|---|---|---|---|---|
| M4 × 12 | 1.23 | M4 × 20 | 1.84 | Quote this size |
| M5 × 16 | 2.59 | M5 × 25 | 3.71 | Quote this size |
| M6 × 16 | 3.76 | M6 × 30 | 6.22 | Quote this size |
| M8 × 20 | 8.6 | M8 × 40 | 14.8 | Quote this size |
| M10 × 25 | 16.6 | M10 × 50 | 30.1 | Quote this size |
| M12 × 30 | 28.5 | M12 × 60 | 54 | Quote this size |
| M16 × 40 | 65.1 | M16 × 80 | 127 | Quote this size |
| M20 × 50 | 123 | M20 × 100 | 253 | Quote this size |
Length is measured including the head
For countersunk screws the nominal length is the overall length, from the top of the head to the tip. This is different from hex bolts and cap screws, where length is measured from under the head. When converting a cap screw design to a flush countersunk screw, add the head height back into the length you order.
Typical commercial lengths are about 6–40 mm for M3, 6–60 mm for M4 and M5, 8–100 mm for M6 to M10, and up to 200 mm for M12, M16 and M20.
Grades, materials and finishes
DIN 7991 screws are mostly supplied in steel 8.8, 10.9 and 12.9 and stainless A2 and A4. Because ISO 10642 no longer covers stainless, many stainless countersunk screws are still sold as DIN 7991. Black oxide and zinc flake are common on 10.9 and 12.9; zinc-plated 10.9 should be baked after plating to control hydrogen embrittlement.
Mistakes to avoid
- Accepting ISO 10642 in place of DIN 7991 (or the reverse) without checking the countersink.
- Ordering length from under the head; countersunk screws are measured overall.
- Expecting full cap screw clamp load. The flat head and shallow socket limit the load, which is why ISO 10642 uses reduced-loadability marking.
- Using M22 or M24 without noting the 60° head; a 90° countersink will not seat it.
How to specify countersunk screws in your RFQ
- Standard: DIN 7991 or ISO 10642, and whether the other is acceptable.
- Size × overall length, e.g. M8 × 30, and quantity per size.
- Property class 8.8, 10.9 or 12.9, or stainless A2-70 / A4-70 / A4-80.
- Finish: black oxide, zinc plated with baking, zinc flake or plain stainless.
- Packaging, labelling and certificates (e.g. EN 10204 3.1).
Order these sizes from HEXVARO
Send your size list with grade, finish and quantity — we reply within 2 working hours with price, lead time and shipping terms.
- Reply: within 2 working hours
- MOQ: 500 pcs per specification
- Lead time: 10–15 days stock items
- Payment: T/T · L/C · PayPal
- Shipping ports: Tianjin · Ningbo · Shanghai · Shenzhen
- Incoterms: EXW · FOB · CFR · CIF · DAP
- Experience: Founder with 10+ years in the fastener industry
Frequently asked questions
Is the length of a countersunk screw measured with the head?
Yes. For countersunk screws the nominal length is measured from the top of the head to the end of the screw.
Is DIN 7991 the same as ISO 10642?
No. ISO 10642 replaced DIN 7991, but its heads are larger and taller. For M8 the DIN head is 16 mm max and the ISO head 17.92 mm (theoretical). The hex key sizes are the same.
What hex key fits an M8 countersunk socket screw?
A 5 mm hex key fits an M8 DIN 7991 or ISO 10642 screw. An M6 takes 4 mm and an M10 takes 6 mm.
Are stainless steel DIN 7991 screws still available?
Yes. ISO 10642 no longer includes stainless steel, so stainless countersunk socket screws are still commonly made and sold to DIN 7991 in A2 and A4.
What is the countersink angle for DIN 7991?
90° for M3 to M20. M22 and M24 have a 60° head.
What is the MOQ for countersunk screws?
Reference MOQ is 500 pcs per specification. Stock sizes typically ship in 10–15 days and made-to-order sizes in 25–30 days, subject to quotation. We reply to every RFQ within 2 working hours.
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