DIN 15401 Part 1: Forged Single Hooks — Unmachined Parts (Complete Technical Reference)

Note: This document is a comprehensive technical reference compiled from publicly available DIN 15401 Part 1 data and industry sources. DIN standards are copyrighted and available for purchase from Beuth Verlag (www.beuth.de). This reference is intended for technical understanding and quick lookup, not as a substitute for the official standard.

1. Standard Title and Scope

Standard: DIN 15401 Part 1

Full Title (German): Lasthaken für Hebezeuge; Einfachhaken; Rohteile

Full Title (English): Lifting hooks for lifting appliances; Single hooks; Unmachined parts

Scope: DIN 15401 Part 1 specifies the dimensions, materials, forging requirements and marking of unmachined forged single hook blanks (rohlinge) for lifting appliances. These blanks are semi-finished forgings that have completed forging and heat treatment, but have not yet undergone thread cutting, final machining or finishing. They are intended for subsequent machining into finished single hooks per DIN 15401 Part 2.

Applicable hook types: Single hooks with threaded shank, available with nose (RSN) or without nose / flat nose (RFN), in hook numbers ranging from 006 to 250.

Relationship to other standards:

• DIN 15400: Lifting hooks — materials, mechanical properties, lifting capacity and stresses (master standard)
• DIN 15401 Part 2: Single hooks — finished parts with threaded shank
• DIN 15402: Ramshorn (double) hooks — Part 1 unmachined, Part 2 finished
• DIN 15404: Technical delivery conditions for forged lifting hooks
• DIN 15411: Hook suspensions
• DIN 15412: Crossheads
• DIN 15413: Nuts

2. Normative References

The following standards contain provisions which, through reference in this text, constitute provisions of DIN 15401 Part 1:

• DIN 15400: Lifting hooks for lifting appliances — Materials, mechanical properties, lifting capacity and stresses
• DIN 15404: Lifting hooks for lifting appliances — Technical delivery conditions for forged lifting hooks
• DIN EN 10025: Hot rolled products of structural steels
• DIN EN 10083: Quenched and tempered steels
• DIN 50125: Tensile test pieces
• DIN 50115: Charpy impact test

3. Terms and Definitions

• Unmachined part (Rohteil): A forged hook blank that has completed forging and heat treatment, with machining allowance reserved for subsequent thread cutting and final machining. Not ready for lifting service.
• Hook number: A numerical designation (006 to 250) that identifies the hook size and corresponds to the shank diameter d1 and nominal lifting capacity.
• Strength grade: Classification of hook material by mechanical properties (M, P, S, T, V), defined in DIN 15400.
• Shank (Schaft): The straight cylindrical portion of the hook that is threaded in the finished part and connects to the hook block via a nut and crosshead.
• Nose (Nase): The protruding tip at the end of the hook throat, designed to prevent sling disengagement. RSN type hooks have a nose; RFN type hooks have a flat or no nose.
• Throat opening (Maulweite): The clear opening between the hook tip and the hook body, through which slings are loaded.

4. Hook Number Series and Types

DIN 15401 Part 1 defines single hook blanks in the following hook numbers:

006, 010, 012, 020, 025, 04, 05, 08, 1, 1.6, 2.5, 4, 5, 6, 8, 10, 12, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250

Two types are specified:

• RSN: Single hook blank with nose, primarily for smaller hook numbers (006 to 8, with some exceptions).
• RFN: Single hook blank without nose / flat nose, primarily for larger hook numbers (10 to 250, with some exceptions at 05 and 08).

The hook number approximately corresponds to the nominal lifting capacity in tons at a reference strength grade and duty class, as defined in DIN 15400. The actual allowable WLL depends on the strength grade (M/P/S/T/V) and the crane mechanism duty class (M1-M8).

5. Materials and Strength Grades

Per DIN 15400, hook blanks are manufactured in five strength grades from lowest to highest: M, P, S, T and V. The material selection depends on the hook number and strength grade as follows:

Hook No. Range	Grade M	Grade P	Grade S	Grade T	Grade V
006 to 1.6	StE-285	StE-355	StE-420 / 34CrMo4	34CrMo4	34CrMo4
2.5 to 40	StE-285	StE-355	StE-420 / 34CrMo4	34CrMo4	34CrNiMo6
50 to 250	StE-355	StE-420	StE-500 / 34CrMo4	34CrNiMo6	34CrNiMo8

Material Notes

• Grades M and P: Fine-grained structural steels (StE-285, StE-355, StE-420), normalized condition. Suitable for general and normal-duty lifting applications.
• Grade S: Structural steel (StE-420, StE-500) or low-alloy steel (34CrMo4). For medium-duty applications with higher load requirements.
• Grade T: Quenched and tempered alloy steel (34CrMo4 or 34CrNiMo6). For medium- to heavy-duty cranes requiring higher strength and toughness.
• Grade V: High-strength quenched and tempered alloy steel (34CrMo4, 34CrNiMo6 or 34CrNiMo8). For heavy-duty and critical lifting applications. Note: Grades T and V are not recommended for metallurgical cranes.
• Chinese equivalents: 34CrMo4 ≈ 35CrMo; 34CrNiMo6 ≈ 34Cr2Ni2Mo; 30CrNiMo8 ≈ 30Cr2Ni2Mo; StE-355 ≈ Q345qD; StE-420 ≈ Q420qD.

6. Dimensional Specifications

The following tables provide the complete dimensional specifications for DIN 15401 Part 1 single hook unmachined parts. All dimensions are in millimeters (mm) unless otherwise noted. Weights are in kilograms (kg).

6.1 Main Dimensions — Small Hook Numbers (006 to 8)

No.	Type	a1	a2	a3	b1	b2	d1	e1	e2	e3	f1	h1	h2	l1
006	RSN	25	20	28	13	11	14	60	60	52	14.5	17	14	100
010	RSN	28	22	32	16	13	16	67	68	60	16.5	20	17	109
012	RSN	30	24	34	19	15	16	71	73	63	18	22	19	115
020	RSN	34	27	39	21	18	20	81	82	70	20	26	22	138
025	RSN	36	28	41	22	19	20	85	88	74	22	28	24	144
04	RSN	40	32	45	27	22	24	96	100	83	25	34	29	155
05	RFN	43	34	48	29	24	24	102	108	89	26	37	31	167
08	RFN	48	38	54	35	29	30	115	120	100	29	44	37	186

6.2 Main Dimensions — Large Hook Numbers (1 to 250)

No.	Type	a1	a2	a3	b1	b2	d1	e1	e2	e3	f1	h1	h2	l1
1	RSN	50	40	57	38	32	30	120	128	105	31	48	40	197
1.6	RSN	56	45	64	45	38	36	135	146	118	35	56	48	224
2.5	RSN	63	50	72	53	45	42	—	—	132	40	67	58	253
4	RSN	71	56	80	63	53	48	172	190	148	45	80	67	285
5	RSN	80	63	90	71	60	53	—	—	165	51	90	75	318
6	RSN	90	71	101	80	67	60	218	240	185	57	100	85	380
8	RSN	100	80	113	90	75	67	242	268	210	64	112	95	418
10	RFN	112	90	127	100	85	75	256	286	221	—	125	106	452
12	RFN	125	100	143	112	95	85	292	316	252	—	140	118	650
16	RFN	140	112	160	125	106	95	325	357	280	—	160	132	730
20	RFN	160	125	180	140	118	106	370	405	330	—	180	150	800
25	RFN	180	140	202	160	132	118	415	455	360	—	200	170	895
32	RFN	200	160	225	180	150	132	465	510	400	—	224	190	970
40	RFN	224	180	252	200	170	150	517	567	447	—	250	212	1041
50	RFN	250	200	285	224	190	170	575	635	485	—	280	236	1200
63	RFN	280	224	320	250	212	190	655	710	550	—	315	265	1320
80	RFN	315	250	358	280	236	212	727	802	598	—	355	300	1470
100	RFN	355	280	402	315	265	236	827	902	688	—	400	335	1615
125	RFN	400	315	450	355	300	265	920	1020	750	—	450	375	1790
160	RFN	450	355	505	400	335	300	1035	1145	825	—	500	425	1990
200	RFN	500	400	565	450	375	335	1150	1275	900	—	560	475	2248
250	RFN	560	450	635	500	425	375	1280	1430	980	—	630	530	2505

6.3 Radii, Transitions and Additional Dimensions (All Hook Numbers)

No.	f2	f3	g1	r1	r2	r3	r4	r5	r6	r7	r8	r9
006	—	—	6.5	2	3	32	53	53	27	26	—	4
010	—	—	7	2	3.5	35	60	60	31	30	—	40
012	—	—	7.5	2.5	4	37	63	63	34	33	—	44
020	—	—	8.5	2.5	4.5	40	71	71	39	37	—	52
025	—	—	9	3	5	43	75	75	42	40	—	56
04	—	—	10	3.5	5.5	46	85	85	49	45	—	68
05	—	—	10.5	4	6	48	90	90	53	48	—	74
08	—	—	12	4.5	7	52	100	100	61	56	—	88
1	—	—	12.5	5	8	55	106	106	65	60	—	96
1.6	—	—	14	6	9	60	118	118	76	68	—	112
2.5	—	—	16	7	10	65	132	132	90	78	—	134
4	—	—	16	8	12	71	150	150	103	90	—	160
5	—	—	18	9	14	80	170	170	114	100	—	180
6	—	—	18	10	16	90	190	190	131	112	—	200
8	—	—	23	11	18	100	212	212	146	125	—	224
10	46	26	23	12	20	65	165	236	163	140	12	250
12	53	34	28	14	22	70	185	265	182	160	16	280
16	58	35	33	16	25	80	210	300	204	180	16	320
20	68	45	33	18	28	90	240	335	232	200	20	360
25	74	45	38	20	32	100	270	375	262	224	20	400
32	80	45	38	22	36	115	300	425	292	250	20	448
40	93	55	42	25	40	130	335	475	326	280	25	500
50	100	55	42	28	45	150	370	530	326	315	25	560
63	108	60	45	32	50	160	420	600	408	355	25	630
80	113	60	45	36	56	180	470	670	460	400	25	710
100	130	70	50	40	63	200	530	750	516	450	30	800
125	138	70	50	45	71	230	600	850	579	500	30	900
160	147	70	55	50	80	250	675	950	654	560	30	1000
200	154	70	55	56	90	285	750	1060	729	630	30	1120
250	164	70	60	63	100	320	840	1180	815	710	30	1260

6.4 Approximate Weights

No.	Weight (kg)	No.	Weight (kg)	No.	Weight (kg)	No.	Weight (kg)
006	0.2	1	3.2	10	34	63	600
010	0.3	1.6	4.5	12	47	80	860
012	0.4	2.5	6.3	16	66	100	1220
020	0.6	4	8.8	20	112	125	1740
025	0.8	5	12.3	25	160	160	2480
04	1.1	6	17.1	32	220	200	3420
05	1.6	8	24	40	310	250	4800
08	2.3	—	—	50	430	—	—

7. Dimension Designations Explained

Symbol	Description
a1, a2, a3	Hook throat and tip dimensions (throat opening related)
b1, b2	Hook body thickness dimensions
d1	Shank diameter (nominal thread diameter for finished part)
e1, e2, e3	Overall width and depth dimensions of hook body
f1, f2, f3	Bearing surface and shoulder dimensions (f2, f3 apply to RFN type large hooks)
g1	Transition radius at shank-hook body junction
h1, h2	Hook depth and throat depth dimensions
l1	Overall length of hook blank (shank + hook body)
r1 to r9	Various fillet and transition radii to reduce stress concentration

8. Forging Requirements

• Forging process: Hook blanks must be manufactured by closed-die forging (drop forging) or hammer forging (free forging). Cast or welded hooks are not permitted under DIN 15401.
• Metal flow lines: The forging process must produce continuous grain flow lines following the hook contour, eliminating internal metallurgical defects such as porosity, inclusions and laminations.
• Material: Only fine-grained killed steel may be used. The steel must be suitable for forging and subsequent heat treatment.
• Machining allowance: Unmachined parts are supplied with sufficient machining allowance on all surfaces that will be subsequently machined (shank, threads, bearing surfaces, throat opening).
• Surface condition: The forged surface must be smooth and free from harmful defects such as cracks, folds, laps and excessive scale. Local indentations at the shank and curved back junction are permitted within specified tolerances.
• Repair welding: Repair welding of hook forgings is not permitted.

9. Heat Treatment Requirements

• Grades M and P: Normalized condition (normalizing heat treatment) to achieve the required mechanical properties for structural steels (StE-285, StE-355, StE-420).
• Grades S, T and V: Quenched and tempered (Q&T) condition. Quenching forms martensite for high hardness and strength; subsequent high-temperature tempering transforms it into tempered sorbite, achieving the optimal strength-toughness balance.
• Heat treatment before delivery: All unmachined hook blanks must be fully heat-treated before delivery. This eliminates the risk of heat-treatment distortion after final machining.
• Mechanical properties: After heat treatment, the material must meet the minimum yield strength, tensile strength, elongation and impact energy (Charpy V-notch) requirements specified in DIN 15400 for the designated strength grade.
• Hardness: Hardness values after heat treatment must fall within the range specified for the material and strength grade.

10. Surface Treatment and Protection

• Hook blanks must be descaled (rust removal) after forging and heat treatment.
• The surface may be protected with a temporary anti-rust coating (e.g. anti-rust oil or paint) for storage and transportation.
• Final surface treatment (painting, powder coating, etc.) is typically applied after machining, per DIN 15401 Part 2 or customer specification.

11. Marking Requirements

Each unmachined hook blank must be permanently marked with the following information, typically on the shank or a non-critical flat surface:

• Hook number (e.g. 10, 20, 50)
• Strength grade (M, P, S, T or V)
• Manufacturer identification (name or trademark)
• Material specification (where required by customer or applicable standard)
• Heat number / batch number for traceability

Marking must be applied by stamping, die-forging or other permanent method that does not create harmful stress concentrations in load-bearing areas.

12. Inspection and Testing

Per DIN 15404 (technical delivery conditions for forged lifting hooks), the following inspections apply:

• Visual inspection: Full surface examination for cracks, folds, laps and other surface defects.
• Dimensional inspection: Verification of key dimensions against the standard tables, with machining allowance confirmed.
• Magnetic particle testing (MT): For detection of surface and near-surface cracks, particularly at the hook throat, shank transition and hook tip.
• Ultrasonic testing (UT): For detection of internal defects such as inclusions, porosity and laminations, when required by the applicable grade or customer specification.
• Chemical composition verification: Material test certificate (e.g. EN 10204 3.1) confirming chemical composition.
• Mechanical property testing: Tensile test and Charpy impact test on test specimens or test coupons, confirming compliance with the designated strength grade per DIN 15400.
• Hardness testing: Verification of hardness after heat treatment.

Important: DIN 15401 Part 1 unmachined hook blanks are NOT ready for lifting service. They must undergo thread cutting, final machining, proof load testing and final marking per DIN 15401 Part 2 before they can be assembled into a hook block and put into lifting operation. Never use an unmachined blank directly for lifting.

13. Relationship to DIN 15401 Part 2 (Finished Parts)

Aspect	DIN 15401 Part 1 (Unmachined)	DIN 15401 Part 2 (Finished)
State	Forged and heat-treated blank	Fully machined, threaded, tested
Shank thread	Not cut (machining allowance)	Threaded per specification
Bearing surfaces	Not machined	Precision machined
Proof load test	Not required (blank stage)	Required (2 x WLL)
Ready for service	No	Yes
Typical user	Crane OEMs with in-house machining	End users, crane assemblers

14. Summary

DIN 15401 Part 1 defines the complete technical specification for forged single hook unmachined parts (blanks), covering hook numbers 006 through 250 in two types (RSN with nose, RFN without nose). The standard specifies dimensions in full detail (28 dimensional symbols per hook size), materials across five strength grades (M, P, S, T, V), forging requirements (closed-die or hammer forging only, no casting or welding), heat treatment (normalized for M/P, quenched and tempered for S/T/V), marking, and inspection requirements. These blanks serve as the standard semi-finished forgings from which finished single hooks per DIN 15401 Part 2 are machined.