Stainless Steel DIN 7991 Countersunk Hex Socket Screw

Wanluo’s China Stainless Steel DIN 7991 Countersunk Hex Socket Screw are manufactured strictly in accordance with German industrial standards, professionally designed for fully flush hidden assembly requirements. Different from protruding cup head and button head socket screws, this series adopts a 90-degree standard tapered countersunk structure, which can be completely embedded into the workpiece after installation with zero protrusion on the surface.

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Product Description

Stainless Steel DIN 7991 Countersunk Hex Socket Screw by Wanluo thoroughly solves the problems of protruding fastener interference, component friction collision and unflat assembly surface in mechanical operation. Combining precise internal hex drive and seamless hidden locking performance, it is an indispensable precision fastener for high-flatness equipment, sliding parts and streamlined structural assembly.

Structural Features & Manufacturing Technology

Stainless Steel DIN 7991 Countersunk Hex Socket Screw adopt integrated cold forging forming and high-precision thread rolling process. The standard tapered countersunk head features accurate angle tolerance, which perfectly fits conventional workpiece counterbore holes to achieve ultra-flush installation. The deepened internal hex socket is precisely formed with smooth inner wall and high torque resistance, effectively preventing tool slipping and hole collapse during high-strength locking. The full and dense thread profile ensures uniform stress and smooth screwing without jamming or tooth slipping. Made of high-purity stainless steel raw materials, the screw body has stable tensile strength, excellent structural toughness and long-term corrosion resistance, maintaining flat assembly accuracy and reliable fastening performance under long-term vibration and alternating load working conditions.

Product Parameter

Parameter Item	Detailed Specification
Product Name	Stainless Steel DIN 7991 Countersunk Hex Socket Screw, Flat Head Allen Screw
Executive Standard	DIN 7991, ISO Standard, GB Standard, Custom Non-standard Dimensions
Available Material	304, 316, 316L Stainless Steel; 2205/2507 Duplex Steel Customizable
Size Range	M2-M20 full standard metric sizes, custom ultra-short/ultra-long screw length
Head Type	90° standard tapered countersunk head, full flush hidden installation
Drive Type	Precision internal hex socket, compatible with standard allen wrenches
Surface Treatment	Pickling & passivation, burr-free smooth surface, uniform anti-corrosion layer
Mechanical Properties	High tensile resistance, strong torque resistance, stable anti-loosening performance
Packaging Method	Moisture-proof inner bag + export carton, pallet packing for bulk orders
Supply Service	Spot bulk supply, non-standard customization, mixed fastener one-stop procurement

Stainless Steel Din 7991 Countersunk Hex Socket Screw

Screw Thread d		M3	M4	M5	M6	M8	M10	M12	(M14)	M16	(M18)	M20	(M22)	M24
P	Pitch	0.5	0.7	0.8	1	1.25	1.5	1.75	2	2	2.5	2.5	2.5	3
α	tol.(+2)	90°	90°	90°	90°	90°	90°	90°	90°	90°	90°	90°	60°	60°
b	L≤125	12	14	16	18	22	26	30	34	38	42	46	50	54
	125＜L≤200	/	/	/	24	28	32	36	40	44	48	52	56	60
	L＞200	/	/	/	/	/	45	49	53	57	61	65	69	73
d_k	max=nominal size	6	8	10	12	16	20	24	27	30	33	36	36	39
d_k	min	5.7	7.64	9.64	11.57	15.57	19.48	23.48	26.48	29.48	32.38	35.38	35.38	38.38
d_s	max=nominal size	3	4	5	6	8	10	12	14	16	18	20	22	24
d_s	min	2.86	3.82	4.82	5.82	7.78	9.78	11.73	13.73	15.73	17.73	19.67	21.67	23.67
e	min	2.3	2.87	3.44	4.58	5.72	6.86	9.15	11.43	11.43	13.72	13.72	16	16
k	max	1.7	2.3	2.8	3.3	4.4	5.5	6.5	7	7.5	8	8.5	13.1	14
s	Nominal Size	2	2.5	3	4	5	6	8	10	10	12	12	14	14
	min	2.02	2.52	3.02	4.02	5.02	6.02	8.025	10.025	10.025	12.032	12.032	14.032	14.032
	max	2.1	2.6	3.1	4.12	5.14	6.14	8.175	10.175	10.175	12.212	12.212	14.212	14.212
t	max=nominal size	1.2	1.8	2.3	2.5	3.5	4.4	4.6	4.8	5.3	5.5	5.9	8.8	10.3
t	min	0.95	1.55	2.05	2.25	3.2	4.1	4.3	4.5	5	5.2	5.6	8.44	9.87

Core Advantages & Industrial Applications

1. Full countersunk flush design realizes zero surface protrusion after installation, completely avoiding friction, collision and jamming of mechanical sliding parts caused by protruding screw heads, ensuring smooth operation of equipment.

2. Standard 90-degree tapered head fits various conventional counterbore holes accurately, realizing seamless fitting assembly, greatly improving workpiece surface flatness and overall equipment precision.

3. Internal hex drive structure supports high-torque locking operation, solving the problem of insufficient tightening force of cross flat head screws, balancing hidden installation and high-strength fastening performance.

4. High-quality stainless steel material features excellent rust resistance and salt spray resistance, adapting to precision automation equipment, outdoor machinery and mildly corrosive working environments for long-term stable use.

5. Universal standard thread specification matches perfectly with our full range of nuts, washers and threaded rods, supporting one-stop supporting fastening and batch procurement for industrial assembly lines.

Stainless Steel Din 7991 Countersunk Hex Socket Screw

FAQ

Q1: What is the difference between Stainless Steel DIN 7991 Countersunk Hex Socket Screw and DIN 912/ISO 7380 screws?

A1: DIN 912 is cup head protruding installation, ISO 7380 is round button head semi-exposed installation, while DIN 7991 is full countersunk flush installation. It is uniquely used for scenarios requiring absolutely flat workpiece surface and no structural interference.

Q2: Is the fastening strength of countersunk hex screws sufficient for precision equipment?

A2: Yes. Adopting integrated cold forging and thickened screw body design, it has high tensile strength and torque resistance. Its fastening stability fully meets the assembly standards of precision machinery and automated equipment.

Q3: Can DIN 7991 screws be completely embedded into the workpiece?

A3: Absolutely. The standard 90° tapered angle matches industrial universal counterbore holes perfectly. After standard tightening, the screw head is completely flush with the workpiece surface without any protrusion.

Q4: Do you support customized special-angle countersunk head screws?

A4: Yes. We support customization of non-standard countersunk angle, screw length and thread pitch, meeting the special assembly requirements of precision molds and special automation equipment.

Q5: What main scenarios are DIN 7991 screws suitable for?

A5: Widely used in precision automation equipment, sliding mechanical parts, mold accessories, flat tooling fixtures, electronic precision instruments and all assembly scenarios requiring ultra-flat surface and zero interference.

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