济南匠人匠心教育

螺纹大径中径小径表

04/24

什么叫螺纹的大径小径?

一句话：牙顶叫大径，牙底叫小径——无论是内螺纹还是外螺纹。如下图所示（左为外螺纹，右为内螺纹）：
图片
至于中径，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
图片

6g公制外螺纹（即常用螺丝）的大径中径小径表

单位：MM
外螺纹规格
大径（牙顶）
中径
小径（牙底）
公称
公称直径
牙距
*大
最小
*大
最小
M1.4
0.3
1.382
1.307
1.187
1.131
1.057
M1.6
0.35
1.581
1.496
1.354
1.291
1.202
M2.0
0.4
1.981
1.886
1.721
1.654
1.548
M2.2
0.45
2.18
2.08
1.888
1.817
1.693
M2.5
0.45
2.48
2.38
2.188
2.117
1.993
M3.0
0.5
2.98
2.874
2.655
2.58
2.439
M3.5
0.6
3.479
3.354
3.089
3.004
2.83
M4.0
0.7
3.978
3.838
3.523
3.433
3.22
M4.5
0.75
4.478
4.338
3.991
3.901
3.666
M5.0
0.8
4.976
4.826
4.456
4.361
4.11
M6.0
1
5.974
5.794
5.325
5.213
4.892
M7.0
1
6.974
6.794
6.325
6.213
5.892
M8.0
1.25
7.972
7.76
7.325
7.213
6.619
M9.0
1.25
8.972
8.76
8.16
8.042
7.619
M10
1.5
9.968
9.732
8.994
8.862
8.344
M11
1.5
10.968
10.732
9.994
9.862
9.344
M12
1.75
11.966
11.701
10.829
10.679
10.072
M14
2
13.962
13.682
12.663
12.503
11.797
M16
2
15.962
15.682
14.663
14.503
13.797
M18
2.5
17.958
17.623
16.663
16.503
15.252
M20
2.5
19.958
19.623
18.334
18.164
17.252


6H公制内螺纹（即常用螺母）的大径中径小径表

接下来是公制6H内螺纹的大径中径小径表：
单位：MM
内螺纹规格
大径（牙底）
中径
小径(牙顶)
公称直径
牙距
*大
最小
*大
最小
M1.4
0.3
1.418
1.28
1.205
1.142
1.075
M1.6
0.35
1.619
1.458
1.373
1.32
1.22
M2.0
0.4
2.019
1.83
1.74
1.679
1.567
M2.2
0.45
2.22
2.003
1.908
1.838
1.713
M2.5
0.45
2.52
2.303
2.303
2.138
2.013
M3.0
0.5
3.02
2.775
2.675
2.599
2.459
M3.5
0.6
3.521
3.222
3.11
3.01
2.85
M4.0
0.7
4.022
3.663
3.545
3.422
3.242
M4.5
0.75
4.522
4.131
4.013
3.878
3.688
M5.0
0.8
5.024
4.605
4.48
4.334
4.134
M6.0
1
6.026
5.5
5.35
5.153
4.917
M7.0
1
7.026
6.5
6.35
6.153
5.917
M8.0
1.25
8.028
7.348
7.188
6.912
6.647
M9.0
1.25
9.028
8.348
8.188
7.912
7.647
M10
1.5
10.032
9.206
9.026
8.676
8.376
M11
1.5
11.032
10.21
10.03
9.676
9.376
M12
1.75
12.034
11.06
10.86
10.44
10.11
M14
2
14.038
12.91
12.7
12.21
11.84
M16
2
16.038
14.91
14.7
14.21
13.84
M18
2
18.038
16.91
16.7
15.74
15.29
M20
2.5
20.042
18.6
18.38
17.74
17.29

美制外螺纹（螺丝）的大径中径小径表

下表中螺纹规格采用美制常用规范如4-40UNC，但其它尺寸统一采用的单位为公制毫米MM：
外螺纹规格
公差等级
大径（外径）
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
11.1277
2A
12.66698
12.46124
11.84148
11.73226
11.1735
3A
12.7
12.49426
11.8745
11.79322
11.2039
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（螺母）的大、中、小径

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

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