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Cross recessed raised countersunk head screws - Type I and IA [Table 7&8]

ASME B 18.6.3 (T8-I/T8-IA) - 2013

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Thread Size
d

10#

12#

14#

d	Nominal Size
L
d_k	max
	min
k	Ref.
f	Ref.
Socket No.
M₁	Ref.
M₂	Ref.
P	Type I	max
		min
	Type IA	max
		min
α	min
	max

0.0600	0.0730	0.0860	0.0990	0.1120	0.1250	0.1380	0.1510	0.1640	0.1900	0.2160	0.2420
1/8	1/8	1/8	1/8	3/16	3/16	3/16	/	1/4	5/16	3/8	/
0.112	0.137	0.162	0.187	0.212	0.237	0.262	0.287	0.312	0.362	0.412	0.462
0.096	0.120	0.144	0.167	0.191	0.215	0.238	0.262	0.285	0.333	0.380	0.427
0.035	0.043	0.051	0.059	0.067	0.075	0.083	0.091	0.100	0.116	0.132	0.148
0.021	0.025	0.029	0.033	0.037	0.041	0.045	0.049	0.052	0.060	0.068	0.076
0	0	1	1	1	2	2	2	2	2	3	3
0.068	0.070	0.106	0.118	0.130	0.152	0.172	0.176	0.186	0.202	0.264	0.282
0.068	0.070	0.106	0.118	0.130	0.152	0.172	0.176	0.186	0.202	0.264	0.282
0.038	0.041	0.062	0.074	0.087	0.074	0.094	0.100	0.108	0.126	0.135	0.156
0.020	0.023	0.045	0.057	0.070	0.050	0.069	0.075	0.084	0.102	0.111	0.131
0.042	0.043	0.062	0.074	0.086	0.074	0.093	0.099	0.108	0.125	0.135	0.153
0.024	0.027	0.046	0.058	0.070	0.056	0.075	0.081	0.090	0.107	0.117	0.135
80°	80°	80°	80°	80°	80°	80°	80°	80°	80°	80°	80°
82°	82°	82°	82°	82°	82°	82°	82°	82°	82°	82°	82°

Thread Size
d

1/4

16#

18#

5/16

20#

24#

3/8

7/16

1/2

9/16

5/8

3/4

d	Nominal Size
L
d_k	max
	min
k	Ref.
f	Ref.
Socket No.
M₁	Ref.
M₂	Ref.
P	Type I	max
		min
	Type IA	max
		min
α	min
	max

0.2500	0.2680	0.2940	0.3125	0.3200	0.3720	0.3750	0.4375	0.5000	0.5625	0.6250	0.7500
7/16	/	/	1/2	/	/	9/16	5/8	3/4	/	/	/
0.477	0.512	0.561	0.597	0.611	0.711	0.717	0.760	0.815	0.932	1.050	1.285
0.442	0.475	0.522	0.556	0.569	0.664	0.670	0.715	0.765	0.878	0.990	1.215
0.153	0.164	0.180	0.191	0.196	0.228	0.230	0.223	0.223	0.260	0.298	0.372
0.079	0.084	0.092	0.099	0.100	0.116	0.117	0.122	0.131	0.150	0.169	0.206
3	3	4	4	4	4	4	4	4	4	5	5
0.284	0.326	0.374	0.384	0.394	0.430	0.404	0.416	0.430	0.462	0.580	0.642
0.284	0.326	0.374	0.384	0.394	0.430	0.404	0.416	0.430	0.450	0.562	0.624
0.156	0.197	0.206	0.218	0.225	0.262	0.237	0.249	0.263	0.296	0.323	0.388
0.131	0.172	0.182	0.194	0.201	0.238	0.213	0.225	0.239	0.272	0.291	0.357
0.155	0.197	0.205	0.215	0.225	0.261	0.235	0.247	0.262	0.285	0.300	0.362
0.137	0.179	0.187	0.197	0.207	0.243	0.217	0.229	0.244	0.267	0.279	0.341
80°	80°	80°	80°	80°	80°	80°	80°	80°	80°	80°	80°
82°	82°	82°	82°	82°	82°	82°	82°	82°	82°	82°	82°

①,Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth decimal place shall be omitted.
②,Sizes 9/16, 5/8, and 3/4 are for machine screws only.
③,Sizes 7, 14, 16, 18, 20, and 24 are for tapping screws only.
④,Machine Screw Length of Thread 1) Sizes No.5 and smaller. Screws of nominal lengths equal to three diameters and shorter shall have full-form threads extending to within one pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than three diameters, up to and including 1-1/8 in., shall have full-form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall, unless otherwise specified, have a minimum length of full-form thread of 1 in. 2) Sizes No.6 and smaller. Screws of nominal lengths equal to three diameters and shorter shall have full-form threads extending to within one pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than three diameters, up to and including 2 in., shall have full-form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall have a minimum length of full-form thread of 1.5 in. unless otherwise specified.

Alternative history

ANSI/ASME B 18.6.3T8 - 2010 ASME B 18.6.3T8-I/T8-IA - 2013

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