螺纹表

牙顶叫大径，牙底叫小径——无论是内螺纹还是外螺纹。

中径，内螺纹外螺纹都一样，指它们的山腰中点的值，中径是一个理论值

标准来源：GB/T197-2018普通螺纹公差

• 6g公制外螺纹（即常用螺丝）的大径中径小径表

外螺纹规格		大径	中径	小径
公称直径	牙距
M1.4	0.3	1.4	1.21	1.07
M1.7	0.35	1.7	1.47	1.31
M2.0	0.4	2	1.74	1.56
M2.3	0.4	2.3	2.04	1.86
M2.5	0.45	2.5	2.21	2
M3.0	0.5	3	2.68	2.45
M3.5	0.6	3.5	3.11	2.84
M4.0	0.7	4	3.55	3.22
M4.5	0.75	4.5	4.01	3.67
M5.0	0.8	5	4.48	4.11
M6.0	1	6	5.35	4.89
M7.0	1	7	6.35	5.89
M8.0	1.25	8	7.19	6.62
M9.0	1.25	9	8.19	7.62
M10	1.5	10	9.03	8.34
M11	1.5	11	10.03	9.34
M12	1.75	12	10.86	10.06
M14	2	14	12.7	12.06
M16	2	16	14.7	13.79
M18	2.5	18	16.7	15.79
M20	2.5	20	18.38	17.23

• 6H公制内螺纹（即常用螺母）的大径中径小径表

内螺纹规格		大径	中径		小径
公称直径	牙距		最大	最小	最大	最小
M1.4	0.3	1.4	1.28	1.205	1.142	1.075
M1.6	0.35	1.6	1.458	1.373	1.32	1.22
M2.0	0.4	2	1.83	1.74	1.679	1.567
M2.2	0.45	2.2	2.003	1.908	1.838	1.713
M2.5	0.45	2.5	2.303	2.303	2.138	2.013
M3.0	0.5	3	2.775	2.675	2.599	2.459
M3.5	0.6	3.5	3.222	3.11	3.01	2.85
M4.0	0.7	4	3.663	3.545	3.422	3.242
M4.5	0.75	4.5	4.131	4.013	3.878	3.688
M5.0	0.8	5	4.605	4.48	4.334	4.134
M6.0	1	6	5.5	5.35	5.153	4.917
M7.0	1	7	6.5	6.35	6.153	5.917
M8.0	1.25	8	7.348	7.188	6.912	6.647
M9.0	1.25	9	8.348	8.188	7.912	7.647
M10	1.5	10	9.206	9.026	8.676	8.376
M11	1.5	11	10.206	10.026	9.676	9.376
M12	1.75	12	11.063	10.863	10.441	10.106
M14	2	14	12.913	12.701	12.21	11.835
M16	2	16	14.913	14.701	14.21	13.835
M18	2	18	16.913	16.701	15.744	15.294
M20	2.5	20	18.6	18.376	17.744	17.294

• 常用美制外螺纹的大径中径小径表

外螺纹规格	公差等级	大径		中径		小径
		Max	Min	Max	Min	Max
1-64UNC	2A	1.83896	1.74244	1.58242	1.53162	1.36652
	3A	1.8542	1.75768	1.59766	d	1.38176
1-72UNF	2A	1.83896	1.75006	1.61036	1.5621	1.41986
	3A	1.8542	1.7653	1.6256	1.59004	1.4351
2-56UNC	2A	2.16916	2.06502	1.87452	1.82118	1.63068
	3A	2.1844	2.08026	1.88976	1.84912	1.64592
2-64UNF	2A	2.16916	2.07264	1.91262	1.86182	1.69672
	3A	2.1844	2.08788	1.92786	1.88976	1.71196
3-48UNC	2A	2.49682	2.38252	2.15392	2.0955	1.86436
	3A	2.5146	2.4003	2.1717	2.12852	1.88214
3-56UNF	2A	2.49682	2.39268	2.20218	2.1463	1.95834
	3A	2.5146	2.41046	2.21996	2.17932	1.97612
4-40UNC	2A	2.82448	2.69494	2.413	2.3495	2.06756
	3A	2.8448	2.71526	2.43332	2.38506	2.08788
4-48UNF	2A	2.82702	2.71272	2.48412	2.42316	2.19456
	3A	2.8448	2.7305	2.5019	2.45618	2.21234
5-40UNC	2A	3.15468	3.02514	2.7432	2.67716	2.39776
	3A	3.175	3.04546	2.76352	2.71526	2.41808
5-44UNF	2A	3.15722	3.0353	2.7813	2.7178	2.46888
	3A	3.175	3.05308	2.79908	2.75082	2.48666
6-32UNC	2A	3.48488	3.33248	2.96926	2.89814	2.54
	3A	3.5052	3.3528	2.98958	2.93624	2.56032
6-40UNF	2A	3.48488	3.35534	3.0734	3.00736	2.72796
	3A	3.5052	3.37566	3.09372	3.04292	2.74828
8-32UNC	2A	4.14274	3.99034	3.62712	3.55346	3.19786
	3A	4.1656	4.0132	3.64998	3.5941	3.22072
8-36UNF	2A	4.14528	4.00558	3.68808	3.61696	3.30454
	3A	4.1656	4.0259	3.7084	3.65506	3.32486
10-24UNC	2A	4.8006	4.61772	4.11226	4.02844	3.54076
	3A	4.826	4.64312	4.13766	4.07416	3.56616
10-32UNF	2A	4.80314	4.65074	4.28752	4.21132	3.85826
	3A	4.826	4.6736	4.31038	4.25196	3.88112
12-24UNC	2A	5.461	5.27812	4.77266	4.6863	4.20116
	3A	5.4864	5.30352	4.79806	4.73202	4.22656
12-28UNF	2A	5.461	5.2959	4.87172	4.79044	4.37896
	3A	5.4864	5.3213	4.89712	4.83616	4.40436
1/4-20UNC	1A	6.32206	6.01218	5.49656	5.35432	4.81076
	2A	6.32206	6.11632	5.49656	5.40258	4.81076
	3A	6.35	6.14426	5.5245	5.45338	4.8387
1/4-28UNF	1A	6.3246	6.07568	5.73532	5.60832	5.24256
	2A	6.3246	6.1595	5.73532	5.6515	5.24256
	3A	6.35	6.1849	5.76072	5.69722	5.26796
5/16-18UNC	1A	7.90702	7.57428	6.99008	6.83514	6.22808
	2A	7.90702	7.68604	6.99008	6.88848	6.22808
	3A	7.9375	7.71652	7.02056	6.94436	6.25856
5/16-24	1A	79095.6	7.63524	7.22122	7.08152	6.64972
	2A	7.90956	7.72668	7.22122	7.12724	6.64972
	3A	7.9375	7.75462	7.24916	7.18058	6.67766
3/8-16UNC	1A	9.49198	9.1313	8.46074	8.29564	7.59968
	2A	9.49198	9.25322	8.46074	8.34898	7.59968
	3A	9.525	9.28624	8.49376	8.40994	7.6327
3/8-24UNF	1A	9.49706	9.22274	8.80872	8.66394	8.23722
	2A	9.49706	9.31418	8.80872	8.7122	8.23722
	3A	9.525	9.34212	8.83666	8.763	8.26516
7/16-14UNC	1A	11.07694	10.68324	9.89838	9.71804	8.91794
	2A	11.07694	10.81532	9.89838	9.779	8.91794
	3A	11.1125	10.85088	9.93394	9.84504	8.9535
7/16-20UNF	1A	11.07948	10.7696	10.93978	10.0965	9.56818
	2A	11.07948	10.87374	10.93978	10.1473	9.56818
	3A	11.1125	10.90676	10.3124	10.20826	9.6012
1/2-13UNC	1A	12.6619	12.24788	11.3919	11.20394	10.25906
	2A	12.6619	12.38504	11.3919	11.2649	10.33526
	3A	12.7	12.42314	11.43	11.33602	10.37336
1/2-20UNF	1A	12.66698	12.3571	11.84148	11.67892	12.52728
	2A	12.66698	12.46124	11.84148	11.73226	12.52728
	3A	12.7	12.49426	11.8745	11.79322	11.19124
9/16-12UNC	1A	14.24686	13.80998	12.87272	12.6746	11.72718
	2A	14.24686	13.9573	12.87272	12.74064	11.72718
	3A	14.2875	13.99794	12.91336	12.8143	11.76782
9/16-18UNF	1A	14.25194	13.9192	13.335	13.16228	12.573
	2A	14.259814	14.03096	13.335	13.2207	12.573
	3A	14.2875	14.06652	13.37056	13.2842	12.60856
5/8-11UNC	1A	15.83436	15.37208	14.33576	14.12494	13.08608
	2A	15.83436	15.52702	14.33576	14.19606	13.08608
	3A	15.875	15.56766	14.3764	14.27226	13.12672
5/8-18UNF	1A	15.83944	15.5067	14.9225	14.7447	14.1605
	2A	15.83944	15.61846	14.9225	14.80312	14.1605
	3A	15.875	15.60322	14.95806	14.86916	14.19606
3/4-10UNC	1A	19.00428	18.51152	17.35328	17.12976	15.97914
	2A	19.00428	18.67662	17.35328	17.20342	15.97914
	3A	19.05	18.72234	17.399	17.28724	16.02486
3/4-16UNF	1A	19.0119	18.65122	17.98066	17.79016	17.1196
	2A	19.0119	18.77314	17.98066	17.85366	17.1196
	3A	19.05	18.81124	18.01876	17.92224	17.1577
7/8-9UNC	1A	22.17674	21.64842	20.34286	20.10156	18.81632
	2A	22.17674	21.82368	20.34286	20.18284	18.81632
	3A	22.225	21.87194	20.39112	20.27174	18.86458
7/8-14UNF	1A	22.18436	21.79066	21.0058	20.80006	20.02536
	2A	22.18436	21.92274	21.0058	20.86864	20.02536
	3A	22.225	21.96338	21.04644	20.9423	20.066
1-8UNC	1A	25.3492	24.7777	23.28672	23.03018	21.56968
	2A	25.3492	24.9682	23.28672	23.114	21.56968
	3A	25.4	25.019	23.33752	23.20798	21.62048
1-14UNF	1A	25.35682	24.96566	24.17826	23.9649	23.19528
	2A	25.35682	25.0952	24.17826	24.03602	23.19528
	3A	25.4	25.13838	24.22144	24.11476	23.23846

• 美制内螺纹的大、中、小径

内螺纹规格	大径	中径		小径
	Min	Min	Max	Min	Max
1-64UNC	1.8542	1.59766	1.6637	1.42494	1.58242
	1.8542	1.59766	1.64592	1.42494	1.58242
1-72UNF	1.8542	1.6256	1.6891	1.4732	1.6129
	1.8542	1.6256	1.67386	1.4732	1.6129
2-56UNC	2.1844	1.88976	1.96088	1.69418	1.87198
	2.1844	1.88976	1.9431	1.69418	1.87198
2-64UNF	2.1844	1.92786	1.99644	1.75514	1.91262
	2.1844	1.92786	1.97866	1.75514	1.91262
3-48UNC	2.5146	2.1717	2.2479	1.94056	2.1463
	2.5146	2.1717	2.22758	1.94056	2.1463
3-56UNF	2.5146	2.21996	2.29108	2.02438	2.1971
	2.5146	2.21996	2.2733	2.02438	2.1971
4-40UNC	2.8448	2.43332	2.51714	2.15646	2.38506
	2.8448	2.43332	2.49428	2.15646	2.38506
4-48UNF	2.8448	2.5019	2.58064	2.27076	2.45872
	2.8448	2.5019	2.56032	2.27076	2.45872
5-40UNC	3.175	2.76352	2.84734	2.48666	2.69748
	3.175	2.76352	2.82702	2.48666	2.69748
5-44UNF	3.175	2.79908	2.88036	2.55016	2.74066
	3.175	2.54508	2.86004	2.55016	2.74066
6-32UNC	3.5052	2.98958	3.08356	2.6416	2.8956
	3.5052	2.98958	3.05816	2.6416	2.8956
6-40UNF	3.5052	3.09372	3.18008	2.8194	3.0226
	3.5052	3.09372	3.15722	2.8194	3.01244
8-32UNC	4.1656	3.64998	3.7465	3.302	3.5306
	4.1656	3.64998	3.7211	3.302	3.52806
8-36UNF	4.1656	3.7084	3.79984	3.4036	3.6068
	4.1656	3.7084	3.77698	3.4036	3.59664
10-24UNC	4.826	4.13766	4.24688	3.683	3.9624
	4.826	4.13766	4.21894	3.683	3.9497
10-32UNF	4.826	4.31038	4.40944	3.9624	4.1656
	4.826	4.31038	4.38404	3.9624	4.16814
12-24UNC	5.4864	4.79806	4.90982	4.3434	4.5974
	5.4864	4.79806	4.88188	4.3434	4.58978
12-28UNF	5.4864	4.89712	5.0038	4.4958	4.7244
	5.4864	4.89712	4.97586	4.4958	4.71678
1/4-20UNC	6.35	5.5245	5.70992	4.9784	5.2578
	6.35	5.5245	5.64896	4.9784	5.2578
	6.35	5.5245	5.61594	4.9784	5.25018
1/4-28UNF	6.35	5.76072	5.92582	5.3594	5.588
	6.35	6.82752	5.86994	5.3594	5.588
	6.35	6.82752	5.842	5.3594	5.5626
5/16-18UNC	7.9375	7.02056	7.22122	6.4008	6.731
	7.9375	7.02056	7.15518	6.4008	6.731
	7.9375	7.02056	7.11962	6.4008	6.6802
5/16-24	7.9375	7.24916	7.4295	6.7818	7.0358
	7.9375	7.24916	7.37108	6.7818	7.0358
	7.9375	7.24916	7.3406	6.7818	6.99516
3/8-16UNC	9.525	8.49376	8.70966	7.7978	8.1534
	9.525	8.49376	8.63854	7.7978	8.1534
	9.525	8.49376	8.60298	7.7978	8.08228
3/8-24UNF	9.525	8.83666	8.83666	8.382	8.636
	9.525	8.83666	8.96112	8.382	8.636
	9.525	8.83666	8.513064	8.382	9.4488
7/16-14UNC	11.1125	9.93394	10.16762	9.144	9.5504
	11.1125	9.93394	10.08888	9.144	9.5504
	11.1125	9.93394	10.05078	9.144	9.44118
7/16-20UNF	11.06678	10.287	10.49274	9.7282	10.033
	11.06678	10.287	10.42416	9.7282	10.033
	11.06678	10.287	10.39114	9.7282	9.94664
1/2-13UNC	12.7	11.43	11.67638	10.5918	11.0236
	12.7	11.43	11.5951	10.5918	11.0236
	12.7	11.43	11.55192	10.5918	10.88136
1/2-20UNF	12.7	11.8745	12.08786	11.3284	11.6078
	12.7	11.8745	12.01674	11.3284	11.6078
	12.7	11.8745	11.98118	11.3284	11.52398
9/16-12UNC	14.2875	12.91336	13.17244	11.9888	12.446
	14.2875	12.91336	14.008608	11.9888	12.446
	14.2875	12.91336	13.04544	11.9888	12.30122
9/16-18UNF	14.2875	13.37056	13.59662	12.7508	13.081
	14.2875	13.37056	13.52042	12.7508	13.081
	14.2875	13.37056	13.48232	12.7508	12.96924
5/8-11UNC	15.875	14.3764	14.64818	13.3858	13.8684
	15.875	14.3764	14.55928	13.3858	13.8684
	15.875	14.3764	14.51356	13.3858	13.69314
5/8-18UNF	15.875	14.95806	15.1892	14.351	14.6812
	15.875	14.95806	15.11046	14.351	14.6812
	15.875	14.95806	15.07236	14.351	14.5542
3/4-10UNC	19.05	17.399	17.6911	16.3068	16.8402
	19.05	17.399	17.59458	16.3068	16.8402
	19.05	17.399	17.54378	16.3068	16.6243
3/4-16UNF	19.05	18.01876	18.26768	17.3228	17.6784
	19.05	18.01876	18.18386	17.3228	17.6784
	19.05	18.01876	18.14322	17.3228	17.54632
7/8-9UNC	22.225	20.84832	20.70354	19.177	19.7612
	22.225	20.84832	20.5994	19.177	19.7612
	22.225	20.84832	20.54606	19.177	19.50974
7/8-14UNF	22.225	21.04644	21.31568	20.2692	20.6756
	22.225	21.04644	21.22424	20.2692	20.6756
	22.225	21.04644	21.18106	20.2692	20.49272
1-8UNC	25.4	23.33752	23.6728	21.971	22.606
	25.4	23.33752	23.56104	21.971	22.606
	25.4	23.33752	23.50516	21.971	22.34438
1-14UNF	25.4	24.22144	24.4983	23.4442	23.8252
	25.4	24.22144	24.40686	23.4442	23.8252
	25.4	24.22144	24.3586	23.4442	23.6601