Socket Products

Flat Socket Cap Screws

Flush, low-profile fastening for countersunk applications.

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82° and 90° countersunk socket screws that finish flush with the mating surface.

Dimensions

Specifications & technical data.

Flat countersunk socket cap screws to ASME B18.3 — the 82° head seats into a countersink and finishes flush with the surface.

Download our flat socket cap screw dimensioning table (PDF)

Dimension locations per ASME B18.3 / IFI · 82° countersunk head

Flat Socket Cap Screw Dimensions (in) — ASME B18.3-2012

Nominal Size (Basic Screw Diameter)		D		A		H	G		P		J		T	F
		Body Diameter		Head Diameter		Head Height (Ref.)	Protrusion Gage Diameter		Protrusion Above Gage		Nominal Hexagon Socket Size		Minimum Key Engagement	Max. Fillet Transition Diameter
		Max.	Min.	Max.	Min.	Head Height (Ref.)	Max.	Min.	Max.	Min.	Nominal Hexagon Socket Size		Minimum Key Engagement	Max. Fillet Transition Diameter
#0	0.0600	0.0600	0.0568	0.138	0.117	0.044	0.078	0.077	0.044	0.026	–	0.0350	0.025	0.072
#1	0.0730	0.0730	0.0695	0.168	0.143	0.054	0.101	0.100	0.048	0.028	–	0.0500	0.031	0.089
#2	0.0860	0.0860	0.0822	0.197	0.168	0.064	0.124	0.123	0.051	0.031	–	0.0500	0.038	0.106
#3	0.0990	0.0990	0.0949	0.226	0.193	0.073	0.148	0.147	0.054	0.033	1/16	0.0620	0.044	0.119
#4	0.1120	0.1120	0.1075	0.255	0.218	0.083	0.172	0.171	0.057	0.036	1/16	0.0620	0.055	0.136
#5	0.1250	0.1250	0.1202	0.281	0.240	0.090	0.196	0.195	0.059	0.037	5/64	0.0780	0.061	0.153
#6	0.1380	0.1380	0.1329	0.307	0.263	0.097	0.220	0.219	0.060	0.037	5/64	0.0780	0.066	0.168
#8	0.1640	0.1640	0.1585	0.359	0.311	0.112	0.267	0.266	0.063	0.039	3/32	0.0940	0.076	0.194
#10	0.1900	0.1900	0.1840	0.411	0.359	0.127	0.313	0.312	0.066	0.041	1/8	0.1250	0.087	0.220
#12	0.2158	0.2158	0.2102	0.450	0.410	0.135	0.360	0.359	0.069	0.042	1/8	0.1250	0.094	0.246
1/4"	0.2500	0.2500	0.2435	0.531	0.480	0.161	0.424	0.423	0.072	0.043	5/32	0.1560	0.111	0.280
5/16"	0.3125	0.3125	0.3053	0.656	0.600	0.198	0.539	0.538	0.078	0.047	3/16	0.1880	0.135	0.343
3/8"	0.3750	0.3750	0.3678	0.781	0.720	0.234	0.653	0.652	0.088	0.050	7/32	0.2190	0.159	0.405
7/16"	0.4375	0.4375	0.4294	0.844	0.781	0.234	0.690	0.689	0.104	0.063	1/4	0.2500	0.159	0.468
1/2"	0.5000	0.5000	0.4919	0.938	0.872	0.251	0.739	0.738	0.131	0.087	5/16	0.3120	0.172	0.530
5/8"	0.6250	0.6250	0.6163	1.188	1.112	0.324	0.962	0.961	0.146	0.096	3/8	0.3750	0.220	0.655
3/4"	0.7500	0.7500	0.7406	1.438	1.355	0.396	1.186	1.185	0.170	0.105	1/2	0.5000	0.220	0.780
7/8"	0.8750	0.8750	0.8647	1.688	1.604	0.468	1.411	1.410	0.165	0.118	9/16	0.5620	0.248	0.905
1"	1.0000	1.0000	0.9886	1.938	1.841	0.540	1.635	1.634	0.181	0.130	5/8	0.6250	0.297	1.030
1-1/8"	1.1250	1.1250	1.1086	2.188	2.079	0.611	1.859	1.858	0.196	0.140	3/4	0.7500	0.325	1.187
1-1/4"	1.2500	1.2500	1.2336	2.438	2.316	0.683	2.083	2.082	0.212	0.150	7/8	0.8750	0.358	1.312
1-3/8"	1.3750	1.3750	1.3568	2.688	2.553	0.755	2.306	2.305	0.228	0.162	7/8	0.8750	0.402	1.437
1-1/2"	1.5000	1.5000	1.4818	2.938	2.791	0.827	2.530	2.529	0.243	0.173	1	1.0000	0.435	1.562

All dimensions in inches, per ASME B18.3-2012. 82° countersunk head; A max is the theoretical sharp diameter. Confirm requirements with our estimating team.

Manufactured to

Standards.

ASME B18.3Socket screw dimensions

ASTM F835Alloy steel button, flat and low head socket screws

ASME B1.1Unified inch screw threads

The buyer’s guide

What are flat socket cap screws?

The flat (countersunk) socket cap screw carries an 82° conical head that seats into a matching countersink, leaving the surface completely flush — no head standing proud, nothing to snag, nothing to shear on a sliding part.

82° countersunk head, hex socket drive
Finishes flush with the surface
Protrusion gaging per B18.3 controls the fit
#0 through 1-1/2″

Other names

Countersunk socket screws
Flat head socket cap screws
FHSCS
CSK socket screws

Tips for purchasing

The countersink angle must match — 82° inch series, not 90° metric.
Flush fit is controlled by the protrusion gage columns — that is what to check on a print.
Key engagement is shallower than a standard SHCS — torque accordingly.
Certs and traceability on request.

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