ISO Metric Screw Thread Tolerances

ISO Metric Screw Thread Tolerances

Optimas are a full-service supply chain and manufacturing solutions provider. Before you design your next product or make updates to an existing product, consider partnering with Optimas to take advantage of our many capabilities.

SPEAK TO AN EXPERT

The International Organization for Standardization (ISO) set the standard for limits of metric screw thread. ISO 965 specifies the basic profile for ISO general purpose metric screw threads (M) conforming to ISO 261.

The information below can be used to calculate the values of thread tolerances defined by ISO 965/1. Screw threads are usually signified by two tolerances. One is for the maximum outside diameter, measured from the major diameter of the thread, and the other is for the pitch diameter, measured from the midpoint of each tooth.

Dimensions in millimetres (mm). Tolerances 6g (6h). For guidance only.

Coarse Thread
Fine Thread

Coarse Thread

Thread Size	Engagement Length From	Engagement Length To	Major Diameter (Max)	Major Diameter (Min)	Pitch Diameter (Max)	Pitch Diameter (Min)	Thread Root Radius (Min)
M1	0.6	1.7	1	0.933	0.838	0.785	0.031
M1.2	0.6	1.7	1.2	1.133	1.038	0.985	0.031
M1.4	0.7	2	1.4	1.325	1.205	1.149	0.038
M1.6	0.8	2.6	1.581	1.496	1.354	1.291	0.044
M1.8	0.8	2.6	1.781	1.696	1.554	1.491	0.044
M2	1	3	1.981	1.886	1.721	1.654	0.05
M2.5	1.3	3.8	2.48	2.38	2.118	2.117	0.056
M3	1.5	4.5	2.98	2.874	2.655	2.58	0.063
M3.5	1.7	5	3.479	3.354	3.089	3.004	0.075
M4	2	6	3.978	3.838	3.523	3.433	0.088
M5	2.5	7.5	4.976	4.826	4.456	4.361	0.1
M6	3	12	5.974	5.794	5.324	5.212	0.125
M7	3	3	6.974	6.794	6.324	6.212	0.125
M8	4	12	7.972	7.76	7.16	7.042	0.156
M10	5	15	9.968	9.732	8.994	8.862	0.188
M12	6	18	11.966	11.701	10.829	10.679	0.219
M14	8	24	13.962	13.682	12.663	12.503	0.25
M16	8	24	15.962	15.682	14.663	14.503	0.25
M18	10	30	17.958	17.623	16.334	16.164	0.313
M20	10	30	19.958	19.623	18.334	18.164	0.313
M22	10	30	21.958	21.623	20.334	20.164	0.313
M24	12	36	23.952	23.577	22.003	21.803	0.375
M27	12	36	26.952	26.577	25.003	24.803	0.375
M30	15	45	29.947	29.522	27.674	27.462	0.438
M33	15	45	32.947	32.522	30.674	30.462	0.438
M36	18	53	35.94	35.465	33.342	33.118	0.5
M39	18	53	38.94	38.465	36.342	36.118	0.5

Fine Thread

Thread Size	Engagement Length From	Engagement Length To	Major Diameter (Max)	Major Diameter (Min)	Pitch Diameter (Max)	Pitch Diameter (Min)	Thread Root Radius (Min)
M8x1	3	9	7.794	7.794	7.324	7.212	0.125
M10x1	3	9	9.974	9.794	9.324	9212	0.156
M10x1.25	4	12	9.972	9.76	9.16	9.042	0.156
M12x1.25	4.5	13	11.972	11.76	11.16	11.028	0.156
M12x1.5	5.6	16	11.968	11.732	10.994	10.854	0.156
M14x1,5	5.6	16	13.968	13.732	12.994	12.854	0.188
M16x1.5	5.6	16	15.968	15.732	14.994	14.854	0.188
M18x1.5	5.6	16	17.968	17.732	16.994	16.854	0.188
M18x2	8	24	17.952	17.682	16.663	0.188	0.188
M20x1.5	5.6	16	19.968	19.732	18.994	18.854	0.188
M20x2	8	24	19.962	19.682	18.663	18.503	0.188
M22x1.5	5.6	16	21.968	21.732	20.994	20.854	0.188
M22x2	8	24	21.962	21.682	20.663	20.503	0.188
M24x2	8.5	25	23.962	23.682	22.663	22.493	0.25
M27x2	8.5	25	26.962	26.682	25.663	25.493	0.25
M30x2	8.5	25	29.962	29.682	28.663	28.493	0.25
M33x2	8.5	25	32.962	32.682	31.663	31.493	0.25
M36x3	12	36	35.952	35.577	34.003	33.803	0.375
M39x3	12	36	38.952	38.577	37.003	36.803	0.375

Let Us Help You Find Efficiencies

ISO Metric Screw Thread Tolerances

Coarse Thread

Fine Thread

Coarse Thread

Fine Thread