What tightening torque should you apply?

There are 3 ways of determining the tightening torque to be applied:

• Following a torque-tightening recommendation
• Following the table giving indications on the traction forces and tightening torque
• Determining the yield of a screwed assembly for the Design, Methods, Research & Development departments

Following a torque-tightening recommendation (pre-determined)

Certain recommendations are expressed as a unit other than Nm.

Units conversion table

Indicative table for the traction forces (Fo) and maximum tightening torque values (Cs) according to the screw quality class, and the screw's friction coefficient and diameter

Ø

Quality class

The screw's quality class corresponds to the resistance of the materials used.

Friction coefficient

The friction coefficient (for standardised screws) to be estimated between 3 lubrication conditions:
μ = 0.10 for well-lubricated phosphate or zinc-plated screws.
μ = 0.15 for black or zinc-plated screws with basic lubrication (delivery state).
μ = 0.20 for dry-fitted coated or uncoated screws.

Screw diameter

The screw's diameter or dimension across flats (per standards ISO 272 and NFE 25-016).

Screws with diameter 3 to 16 mm

		Screw Ø (mm)	3	4	5	6	8	10	12	14	16
		Pitch (mm)	0,5	0,7	0,8	1	1,25	1,5	1,75	2	2
Quality class	μ	Dimension across flats (mm)	5,5	7	8	10	13	16	18	21	24
Rm = 600 N/mm² Re = 400 N/mm²	0,10	Cs (Nm)	0,71	1,65	3,25	5,6	13,6	27	46	75	115
		Fo (max (N))	1724	2988	4885	6896	12647	20128	29339	40280	55356
	0.15	Cs (Nm)	0,91	2,09	4,14	7,1	17,4	34	59	95	148
		Fo (max (N))	1556	2696	4414	6226	11432	18206	26550	36463	50216
	0.20	Cs (Nm)	1,06	2,42	4,81	8,3	20	40	69	111	174
		Fo (max (N))	1399	2422	3970	5598	10283	16382	23895	32822	45248
Rm = 800 N/mm² Re = 640 N/mm²	0.10	Cs (Nm)	0,95	2,2	4,34	7,5	18,2	36	62	99	153
		Fo (max (N))	2298	3985	6514	9195	16863	26838	39119	53707	73808
	0.15	Cs (Nm)	1,21	2,78	5,5	9,5	23	46	79	127	198
		Fo (max (N))	2075	3594	5836	8302	15242	24275	35401	48618	66955
	0.20	Cs (Nm)	1,41	3,22	6,4	11,1	27	53	92	148	232
		Fo (max (N))	1866	3230	5293	7464	13710	21843	31860	43763	60331
Rm = 1 000 N/mm² Re = 900 N/mm²	0.10	Cs (Nm)	1,4	3,23	6,3	11	26	52	91	145	225
		Fo (max (N))	3376	5853	9568	13506	24768	39418	57457	78882	108406
	0.15	Cs (Nm)	1,79	4,09	8,1	14	34	67	116	187	291
		Fo (max (N))	3048	5279	8645	12194	22388	35655	51995	71408	98340
	0.20	Cs (Nm)	2,07	4,74	9,4	16,3	39	78	136	218	341
		Fo (max (N))	2740	4744	7774	10962	20137	32082	46795	64277	88611
Rm = 1200 N/mm² Re = 1080 N/mm²	0.10	Cs (Nm)	1,64	3,78	7,4	12,6	31	61	106	170	263
		Fo (max (N))	3951	6849	11196	15805	28984	46128	67236	92309	126858
	0.15	Cs (Nm)	2,09	4,79	9,5	16,4	40	79	136	219	341
		Fo (max (N))	3567	6178	10116	14269	26198	41724	60845	83563	115079
	0.20	Cs (Nm)	2,43	5,5	11	19,1	46	92	159	255	399
		Fo (max (N))	3207	5552	9098	12828	23565	37542	54760	75218	103964

Screws with diameter 18 to 39 mm

		Screw Ø (mm)	18	20	22	24	27	30	33	36	39
		Pitch (mm)	2,5	2,5	2,5	3	3	3,5	3,5	4	4
Quality class	μ	Dimension across flats (mm)	27	30	34	36	41	46	50	55	60
Rm = 600 N/mm² Re = 400 N/mm²	0.10	Cs (Nm)	159	225	307	387	569	773	1046	1346	1741
		Fo (max (N))	67351	86494	108017	124552	163829	199185	242132	291252	349868
	0.15	Cs (Nm)	205	291	400	500	741	1005	1366	1754	2279
		Fo (max (N))	60998	78463	98123	112986	148868	180872	225614	264655	318257
	0.20	Cs (Nm)	239	341	470	586	871	1180	1607	2060	2683
		Fo (max (N))	54919	70700	89478	101809	134257	163062	203536	238679	287179
Rm = 800 N/mm² Re = 640 N/mm²	0.10	Cs (Nm)	213	300	409	516	759	1031	1395	1794	2321
		Fo (max (N))	89802	115326	144023	166069	218439	265581	33843	388336	446491
	0.15	Cs (Nm)	274	388	533	667	989	1341	1822	2339	3038
		Fo (max (N))	81330	104617	130830	150649	198491	261163	300819	352873	424342
	0.20	Cs (Nm)	319	454	626	781	1162	1573	2143	2747	3578
		Fo (max (N))	73225	94267	117970	135745	179009	217417	271382	318238	382906
Rm = 1 000 N/mm² Re = 900 N/mm²	0.10	Cs (Nm)	313	440	602	758	1114	1515	2048	2636	3410
		Fo (max (N))	131897	169385	211534	243914	320832	390072	485926	570369	685159
	0.15	Cs (Nm)	402	570	783	981	1452	1969	2676	3435	4463
		Fo (max (N))	119454	153657	192157	221266	291534	354209	441828	518282	623253
	0.20	Cs (Nm)	469	667	920	1148	1706	2311	3148	4036	5255
		Fo (max (N))	107549	138456	173269	199376	262920	319331	398593	467413	502393
Rm = 1200 N/mm² Re = 1080 N/mm²	0.10	Cs (Nm)	366	515	704	887	1304	1773	2397	3085	3990
		Fo (max (N))	154384	198216	247540	285432	375442	456467	568637	667453	801782
	0.15	Cs (Nm)	471	667	917	1148	1700	2305	3132	4020	5223
		Fo (max (N))	139787	179811	224865	258928	341157	414500	517033	606501	729339
	0.20	Cs (Nm)	549	781	1077	1343	1997	2704	3684	4723	6150
		Fo (max (N))	128856	162023	202762	233313	307672	373685	466438	546973	658229

Determine the tightening torque for the Design, Methods, Research & Development departments,

By exerting a given force, the Dynalight Force torque wrench makes it possible to determine the yield of a screwed assembly and the torque value required.

This wrench is an essential tool for Design Offices and for elastic assemblies or assemblies subject to sealing.

DYNALIGHT® force electronic wrenches for rectangular ends

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DYNALIGHT® force electronic wrenches for round ends

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