Screws · ASME B18.6.3

A4 (316) Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips)

Mechanical properties, corrosion behaviour and the full dimensional range for this grade.

A4 Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips) are supplied to ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80. Corrosion behaviour is superior, including marine and chloride environments, the material is largely non-magnetic, and the usable service range is approx. -200 °C to +400 °C, subject to the property class and the joint. In practice this grade is specified for marine, coastal and chemical applications.

Grade: ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
Corrosion resistance: Superior, including marine and chloride environments
Magnetic response: Largely non-magnetic
Service temperature: approx. -200 °C to +400 °C, subject to the property class and the joint

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

A4 Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips) combine the dimensional form of ASME B18.6.3 with the material properties of grade ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80: superior, including marine and chloride environments, largely non-magnetic, service range approx. -200 °C to +400 °C, subject to the property class and the joint. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.

Why Choose A4 Stainless Steel for Flat Head Machine Screws, UNC (Slotted and Phillips)

Specified for marine, coastal and chemical applications. For flat head machine screws, unc (slotted and phillips), this matters when superior, including marine and chloride environments is the primary requirement.

Mechanical & Physical Properties

Grade designation	ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
Magnetic response	Largely non-magnetic
Service temperature	approx. -200 °C to +400 °C, subject to the property class and the joint
Corrosion characteristic	Superior, including marine and chloride environments

Galvanic & Galling Considerations

Two important notes for stainless flat head machine screws, unc (slotted and phillips): (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.

Comparable Grades

For Flat Head Machine Screws, UNC (Slotted and Phillips), the alternative stainless grade is A2 (304). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.

Using Stainless Fasteners in Aluminum

The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.

Sizes of Flat Head Machine Screws, UNC (Slotted and Phillips) Available in A4 Stainless Steel

Size	Type	Pitch P (mm)	b (mm)	Head diameter dk (mm)	dk_mean (mm)	Head height k (mm)	n_min (mm)	r (mm)	t_mean (mm)	Length range l (in)	Reference standard
#0	Slotted countersunk flat head screws	0.318	3.696	2.845	2.642	0.889	0.495	0.152	0.318	1/16"~1 1/2"	ASME B18.6.3
#0	Cross recessed countersunk flat head screws	0.318	3.696	2.845	2.642	0.889	0.495	0.152	0.318	1/16"~1 1/2"	ASME B18.6.3
#1	Slotted countersunk flat head screws	0.397	4.497	3.48	3.264	1.092	0.572	0.185	0.394	1/16"~1 1/2"	ASME B18.6.3
#1	Cross recessed countersunk flat head screws	0.397	4.497	3.48	3.264	1.092	0.572	0.185	0.394	1/16"~1 1/2"	ASME B18.6.3
#2	Slotted countersunk flat head screws	0.454	5.298	4.115	3.886	1.295	0.686	0.218	0.483	1/16"~2 1/2"	ASME B18.6.3
#2	Cross recessed countersunk flat head screws	0.454	5.298	4.115	3.886	1.295	0.686	0.218	0.483	1/16"~2 1/2"	ASME B18.6.3
#3	Slotted countersunk flat head screws	0.529	6.098	4.75	4.496	1.499	0.787	0.251	0.559	1/8"~2 1/2"	ASME B18.6.3
#3	Cross recessed countersunk flat head screws	0.529	6.098	4.75	4.496	1.499	0.787	0.251	0.559	1/8"~2 1/2"	ASME B18.6.3
#4	Slotted countersunk flat head screws	0.635	6.899	5.385	5.118	1.702	0.889	0.284	0.635	1/8"~4"	ASME B18.6.3
#4	Cross recessed countersunk flat head screws	0.635	6.899	5.385	5.118	1.702	0.889	0.284	0.635	1/8"~4"	ASME B18.6.3
#5	Slotted countersunk flat head screws	0.635	7.7	6.02	5.74	1.905	0.991	0.318	0.711	3/16"~4"	ASME B18.6.3
#5	Cross recessed countersunk flat head screws	0.635	7.7	6.02	5.74	1.905	0.991	0.318	0.711	3/16"~4"	ASME B18.6.3
#6	Slotted countersunk flat head screws	0.794	8.501	6.655	6.35	2.108	1.105	0.351	0.787	1/8"~4"	ASME B18.6.3
#6	Cross recessed countersunk flat head screws	0.794	8.501	6.655	6.35	2.108	1.105	0.351	0.787	1/8"~4"	ASME B18.6.3
#8	Slotted countersunk flat head screws	0.794	10.102	7.925	7.582	2.54	1.257	0.417	0.94	1/8"~5"	ASME B18.6.3
#8	Cross recessed countersunk flat head screws	0.794	10.102	7.925	7.582	2.54	1.257	0.417	0.94	1/8"~5"	ASME B18.6.3
#10	Slotted countersunk flat head screws	1.058	11.704	9.195	8.826	2.946	1.397	0.483	1.105	3/16"~8"	ASME B18.6.3
#10	Cross recessed countersunk flat head screws	1.058	11.704	9.195	8.826	2.946	1.397	0.483	1.105	3/16"~8"	ASME B18.6.3
#12	Slotted countersunk flat head screws	1.058	13.306	10.465	10.058	3.353	1.562	0.549	1.257	1/4"~8"	ASME B18.6.3
#12	Cross recessed countersunk flat head screws	1.058	13.306	10.465	10.058	3.353	1.562	0.549	1.257	1/4"~8"	ASME B18.6.3
1/4"	Slotted countersunk flat head screws	1.27	15.4	12.116	11.671	3.886	1.765	0.635	1.473	3/8"~10"	ASME B18.6.3
1/4"	Cross recessed countersunk flat head screws	1.27	15.4	12.116	11.671	3.886	1.765	0.635	1.473	3/8"~10"	ASME B18.6.3
5/16"	Slotted countersunk flat head screws	1.411	19.25	15.164	14.643	4.851	1.981	0.794	1.854	1/2"~10"	ASME B18.6.3
5/16"	Cross recessed countersunk flat head screws	1.411	19.25	15.164	14.643	4.851	1.981	0.794	1.854	1/2"~10"	ASME B18.6.3
3/8"	Slotted countersunk flat head screws	1.587	23.1	18.212	17.615	5.842	2.223	0.953	2.235	1/2"~12"	ASME B18.6.3
3/8"	Cross recessed countersunk flat head screws	1.587	23.1	18.212	17.615	5.842	2.223	0.953	2.235	1/2"~12"	ASME B18.6.3
7/16"	Slotted countersunk flat head screws	1.814	26.95	19.304	18.733	5.664	2.223	1.111	2.146	3/4"~12"	ASME B18.6.3
7/16"	Cross recessed countersunk flat head screws	1.814	26.95	19.304	18.733	5.664	2.223	1.111	2.146	3/4"~12"	ASME B18.6.3
1/2"	Slotted countersunk flat head screws	1.954	30.8	20.701	20.066	5.664	2.502	1.27	2.134	3/4"~12"	ASME B18.6.3
1/2"	Cross recessed countersunk flat head screws	1.954	30.8	20.701	20.066	5.664	2.502	1.27	2.134	3/4"~12"	ASME B18.6.3

Dimensions are independent of the material: every size above is available in A4 Stainless Steel.

Custom manufacturing · Made to drawing

Need this screw in a grade that is not listed?

A4 Stainless Steel is one of the grades the catalog describes. Thread size and pitch, length, property class, drive form, head geometry and head marking are all specifiable — the standard part is where it starts, not where it stops. Made by cold heading or warm forging.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

Custom screw manufacturing Send a drawing

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Dimensioned line drawing of #0 Flat Head Machine Screws, UNC (Slotted and Phillips) to ASME B18.6.3. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

Type: Slotted countersunk flat head screws
Pitch P (mm): 0.318
b (mm): 3.696
Head diameter dk (mm): 2.845
dk_mean (mm): 2.642
Head height k (mm): 0.889
n_min (mm): 0.495
r (mm): 0.152
t_mean (mm): 0.318
Length range l (in): 1/16"~1 1/2"

Sends the selected values to the quote form below.

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The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

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Specification

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Notes

Dimensions & Specifications (ASME B18.6.3)

Size	Type	Pitch P (mm)	b (mm)	Head diameter dk (mm)	dk_mean (mm)	Head height k (mm)	n_min (mm)	r (mm)	t_mean (mm)	Length range l (in)	Reference standard
#0	Slotted countersunk flat head screws	0.318	3.696	2.845	2.642	0.889	0.495	0.152	0.318	1/16"~1 1/2"	ASME B18.6.3
#0	Cross recessed countersunk flat head screws	0.318	3.696	2.845	2.642	0.889	0.495	0.152	0.318	1/16"~1 1/2"	ASME B18.6.3
#1	Slotted countersunk flat head screws	0.397	4.497	3.48	3.264	1.092	0.572	0.185	0.394	1/16"~1 1/2"	ASME B18.6.3
#1	Cross recessed countersunk flat head screws	0.397	4.497	3.48	3.264	1.092	0.572	0.185	0.394	1/16"~1 1/2"	ASME B18.6.3
#2	Slotted countersunk flat head screws	0.454	5.298	4.115	3.886	1.295	0.686	0.218	0.483	1/16"~2 1/2"	ASME B18.6.3
#2	Cross recessed countersunk flat head screws	0.454	5.298	4.115	3.886	1.295	0.686	0.218	0.483	1/16"~2 1/2"	ASME B18.6.3
#3	Slotted countersunk flat head screws	0.529	6.098	4.75	4.496	1.499	0.787	0.251	0.559	1/8"~2 1/2"	ASME B18.6.3
#3	Cross recessed countersunk flat head screws	0.529	6.098	4.75	4.496	1.499	0.787	0.251	0.559	1/8"~2 1/2"	ASME B18.6.3
#4	Slotted countersunk flat head screws	0.635	6.899	5.385	5.118	1.702	0.889	0.284	0.635	1/8"~4"	ASME B18.6.3
#4	Cross recessed countersunk flat head screws	0.635	6.899	5.385	5.118	1.702	0.889	0.284	0.635	1/8"~4"	ASME B18.6.3
#5	Slotted countersunk flat head screws	0.635	7.7	6.02	5.74	1.905	0.991	0.318	0.711	3/16"~4"	ASME B18.6.3
#5	Cross recessed countersunk flat head screws	0.635	7.7	6.02	5.74	1.905	0.991	0.318	0.711	3/16"~4"	ASME B18.6.3
#6	Slotted countersunk flat head screws	0.794	8.501	6.655	6.35	2.108	1.105	0.351	0.787	1/8"~4"	ASME B18.6.3
#6	Cross recessed countersunk flat head screws	0.794	8.501	6.655	6.35	2.108	1.105	0.351	0.787	1/8"~4"	ASME B18.6.3
#8	Slotted countersunk flat head screws	0.794	10.102	7.925	7.582	2.54	1.257	0.417	0.94	1/8"~5"	ASME B18.6.3
#8	Cross recessed countersunk flat head screws	0.794	10.102	7.925	7.582	2.54	1.257	0.417	0.94	1/8"~5"	ASME B18.6.3
#10	Slotted countersunk flat head screws	1.058	11.704	9.195	8.826	2.946	1.397	0.483	1.105	3/16"~8"	ASME B18.6.3
#10	Cross recessed countersunk flat head screws	1.058	11.704	9.195	8.826	2.946	1.397	0.483	1.105	3/16"~8"	ASME B18.6.3
#12	Slotted countersunk flat head screws	1.058	13.306	10.465	10.058	3.353	1.562	0.549	1.257	1/4"~8"	ASME B18.6.3
#12	Cross recessed countersunk flat head screws	1.058	13.306	10.465	10.058	3.353	1.562	0.549	1.257	1/4"~8"	ASME B18.6.3
1/4"	Slotted countersunk flat head screws	1.27	15.4	12.116	11.671	3.886	1.765	0.635	1.473	3/8"~10"	ASME B18.6.3
1/4"	Cross recessed countersunk flat head screws	1.27	15.4	12.116	11.671	3.886	1.765	0.635	1.473	3/8"~10"	ASME B18.6.3
5/16"	Slotted countersunk flat head screws	1.411	19.25	15.164	14.643	4.851	1.981	0.794	1.854	1/2"~10"	ASME B18.6.3
5/16"	Cross recessed countersunk flat head screws	1.411	19.25	15.164	14.643	4.851	1.981	0.794	1.854	1/2"~10"	ASME B18.6.3
3/8"	Slotted countersunk flat head screws	1.587	23.1	18.212	17.615	5.842	2.223	0.953	2.235	1/2"~12"	ASME B18.6.3
3/8"	Cross recessed countersunk flat head screws	1.587	23.1	18.212	17.615	5.842	2.223	0.953	2.235	1/2"~12"	ASME B18.6.3
7/16"	Slotted countersunk flat head screws	1.814	26.95	19.304	18.733	5.664	2.223	1.111	2.146	3/4"~12"	ASME B18.6.3
7/16"	Cross recessed countersunk flat head screws	1.814	26.95	19.304	18.733	5.664	2.223	1.111	2.146	3/4"~12"	ASME B18.6.3
1/2"	Slotted countersunk flat head screws	1.954	30.8	20.701	20.066	5.664	2.502	1.27	2.134	3/4"~12"	ASME B18.6.3
1/2"	Cross recessed countersunk flat head screws	1.954	30.8	20.701	20.066	5.664	2.502	1.27	2.134	3/4"~12"	ASME B18.6.3
9/16"	Slotted countersunk flat head screws	2.167	34.65	23.673	22.987	6.604	2.794	1.429	2.502	3/4"~12"	ASME B18.6.3
9/16"	Cross recessed countersunk flat head screws	2.167	34.65	23.673	22.987	6.604	2.794	1.429	2.502	3/4"~12"	ASME B18.6.3
5/8"	Slotted countersunk flat head screws	2.309	38.5	26.67	25.908	7.569	3.162	1.587	2.857	3/4"~14"	ASME B18.6.3
5/8"	Cross recessed countersunk flat head screws	2.309	38.5	26.67	25.908	7.569	3.162	1.587	2.857	3/4"~14"	ASME B18.6.3
3/4"	Slotted countersunk flat head screws	2.54	46.2	32.639	31.75	9.449	3.556	1.905	3.581	1"~14"	ASME B18.6.3
3/4"	Cross recessed countersunk flat head screws	2.54	46.2	32.639	31.75	9.449	3.556	1.905	3.581	1"~14"	ASME B18.6.3

Materials & Grades

Select a material class to see the grades we supply it in. Each designation is listed with its ISO/EN, AISI/SAE, JIS and GB equivalents.

Stainless Steel38 Carbon Steel66 Alloy Steel41 Bearing Steel5 Spring Steel25 Aluminum and Aluminum Alloys21 Brass17 Bronze11 Copper8 Titanium and Titanium Alloys18 Nickel and Nickel Alloys22 Iron-Nickel and High-Temperature Alloys10 Tool Steel and Specialty Hardened Steel9 Structural and Construction Steel9

Stainless Steel

Austenitic Stainless Steel

A1 AISI 303 · SAE 303 · SUS303 · EN 1.4305 · X8CrNiS18-9
A2 AISI 304 · SAE 304 · SUS304 · EN 1.4301 · X5CrNi18-10 · 06Cr19Ni10
304L AISI 304L · SUS304L · EN 1.4307 · X2CrNi18-9 · 022Cr19Ni10
302 AISI 302 · SUS302 · EN 1.4310
305 AISI 305 · SUS305 · EN 1.4303
A4 AISI 316 · SAE 316 · SUS316 · EN 1.4401 · X5CrNiMo17-12-2 · 06Cr17Ni12Mo2
316L AISI 316L · SUS316L · EN 1.4404 · X2CrNiMo17-12-2 · 022Cr17Ni12Mo2
321 AISI 321 · SUS321 · EN 1.4541 · X6CrNiTi18-10
310 / 310S AISI 310 · AISI 310S · SUS310S · EN 1.4845
302HQ AISI 302HQ
A3
A5
347 AISI 347 · SUS347 · EN 1.4550 · X6CrNiNb18-10
309 / 309S AISI 309 · AISI 309S · SUS309S

Martensitic Stainless Steel

AISI 410 SUS410 · EN 1.4006 · X12Cr13 · 12Cr13
AISI 420 SUS420J1 · SUS420J2 · EN 1.4021 · EN 1.4028 · 20Cr13 · 30Cr13
AISI 431 SUS431 · EN 1.4057 · X17CrNi16-2
C1
C3
C4
AISI 440A
AISI 440B
AISI 440C SUS440C · EN 1.4125

Ferritic Stainless Steel

AISI 430 SUS430 · EN 1.4016 · X6Cr17 · 10Cr17
F1
AISI 434
AISI 444

Precipitation-Hardening Stainless Steel

17-4 PH AISI 630 · UNS S17400 · SUS630 · EN 1.4542 · X5CrNiCuNb16-4
15-5 PH UNS S15500
17-7 PH UNS S17700

Duplex and Super Duplex Stainless Steel

Duplex 2205 UNS S31803 · UNS S32205 · EN 1.4462
Super Duplex 2507 UNS S32750 · EN 1.4410
D2
D4
D6
D8
Lean Duplex 2101 UNS S32101
Super Duplex S32760 UNS S32760 · EN 1.4501

Carbon Steel

Low-Carbon Steel

SAE 1006
SAE 1008
SAE 1010
SAE 1018
SAE 1020
Q195
Q235
SAE 1012
SAE 1015
Q215
ML08
ML08Al
ML10
ML15
ML20
SWRCH6A
SWRCH8A
SWRCH10A
SWRCH12A
SWRCH15A
SWRCH18A

Medium-Carbon Steel

SAE 1035
SAE 1045
S45C
C45
SAE 1030
SAE 1040
SAE 1050
30
35
40
45
50
S35C
S40C
S50C
C35
C40

High-Carbon Steel

SAE 1060
SAE 1070
65Mn
SAE 1065
SAE 1075
SAE 1080
SAE 1085
SAE 1090
SAE 1095
60
65
70
75
80
85

Cold-Heading Steel

SWRCH22A
10B21
SWRCH22K
SWRCH25K
SWRCH30K
SWRCH35K
SWRCH40K
ML20Mn
ML25
ML30
ML35
ML40
15B25

Alloy Steel

Chromium Steel

40Cr
45Cr
AISI 5140
SAE 5140
AISI 5120
SAE 5120
SCr420
SCr440

Chromium-Molybdenum Steel

35CrMo
42CrMo
AISI 4140
SCM435
SCM440
42CrMo4
30CrMo
AISI 4130
SAE 4130
SAE 4140
AISI 4142
AISI 4145
SCM415
SCM420
SCM445
EN 1.7220
EN 1.7225
25CrMo4
34CrMo4

Nickel-Chromium-Molybdenum Steel

AISI 4340
SAE 4340
40CrNiMo
SNCM439
EN 1.6511
36CrNiMo4

Boron Alloy Steel

10B22
10B21
15B21
15B25
20MnTiB
20Mn2B
35VB
40MnB

Bearing Steel

GCr15
AISI 52100 SAE 52100 · UNS G52986
SUJ2
100Cr6 EN 1.3505
GCr15SiMn

Spring Steel

Carbon Spring Steel

SAE 1065
SAE 1070
SAE 1075
SAE 1080
SAE 1095
65
70
75
80
65Mn

Silicon-Manganese Spring Steel

60Si2Mn
60Si2MnA
SUP6
SUP7

Chromium-Vanadium Spring Steel

50CrVA
SAE 6150
AISI 6150
SUP10

Stainless Spring Steel

AISI 301
SUS301
EN 1.4310
AISI 302
AISI 304
AISI 316
17-7 PH

Aluminum and Aluminum Alloys

Commercially Pure Aluminum

1050
1060
1070
1100

2xxx Series Aluminum

2024
2011
2014
2017

5xxx Series Aluminum

5052
5083
5754

6xxx Series Aluminum

6061
6061-T6
6063
6082
6082-T6

7xxx Series Aluminum

7075
7075-T6
7005
7050
7075-T73

Brass

Free-Cutting Brass

C36000
H62
HPb59-1
C3601
C3602
C3604
CuZn36Pb3
CuZn39Pb3
EN CW614N
EN CW617N
H65

Lead-Free Brass

C69300
C27450
CW510L
CW511L

Naval Brass

C46400
CuZn39Sn1

Bronze

Silicon Bronze

C65500
C65100
C65600

Phosphor Bronze

C51000
C52100
CuSn6
CuSn8

Aluminum Bronze

C95400
C95500
C63000
CuAl10Ni5Fe4

Copper

C11000
T2
C10100
C10200
C12200
T1
TU1
TU2

Titanium and Titanium Alloys

Commercially Pure Titanium

Grade 2
Grade 1
Grade 3
Grade 4
TA1
TA2
TA3

Alpha-Beta Titanium Alloys

Grade 5
Ti-6Al-4V
TC4
UNS R56400

Low-Interstitial Grade

Grade 23
Ti-6Al-4V ELI
UNS R56407

Other Titanium Fastener Alloys

Ti-6Al-6V-2Sn
Ti-6Al-2Sn-4Zr-2Mo
Beta-C titanium
Ti-10V-2Fe-3Al

Nickel and Nickel Alloys

Commercially Pure Nickel

Nickel 200
UNS N02200
Nickel 201
UNS N02201

Inconel Alloys

Inconel 625 UNS N06625
Inconel 718 UNS N07718
Inconel 600 UNS N06600
Inconel 601 UNS N06601
Inconel 686 UNS N06686
Inconel X-750 UNS N07750

Monel Alloys

Monel 400 UNS N04400
Monel K-500 UNS N05500

Hastelloy Alloys

Hastelloy C-276 UNS N10276
Hastelloy C-22 UNS N06022
Hastelloy B-2 UNS N10665
Hastelloy B-3 UNS N10675
Hastelloy X UNS N06002

Other Nickel Alloys

Alloy 20 UNS N08020
Alloy 625
Alloy 718
Alloy 825 UNS N08825
Alloy 925 UNS N09925

Iron-Nickel and High-Temperature Alloys

A286

A-286
UNS S66286
EN 1.4980

Invar

Invar 36
Alloy 36
UNS K93600
FeNi36

Alloy 42

Alloy 42
UNS K94100
FeNi42

Tool Steel and Specialty Hardened Steel

AISI D2
AISI H13
SKD11
Cr12MoV
AISI O1
AISI A2
AISI S7
SKD61
9CrSi

Structural and Construction Steel

ASTM A36
Q235B
Q355B
S355JR
Q235C
Q355C
S235JR
S275JR
S355J2

Applications & Industries

The sectors that buy Flat Head Machine Screws to ASME B18.6.3, and the duty each one buys them for. Stocked from #0 to 3/4" (screw size).

Industries that specify Flat Head Machine Screws

Appliances inch hardware.
Hardware hinges.
Aerospace ground support flush panels.
Electronics panels.
Energy & infrastructure Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
Maintenance & MRO Stocked replacements matched to an existing property class, thread and finish.

Typical applications

inch threads
slotted or Phillips
machine screw sizes
flush fixing
bolting brackets, motors and gearboxes to a frame
assemblies that are dismantled for service and re-torqued

Service conditions to specify against

Marine and coastal: Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
High load: Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
Torque and preload: The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.

Where to use something else

Do not seat in a metric countersink; 82° inch heads differ from 90° metric.
Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.

Full application guide: where Flat Head Machine Screws are used, how to specify them, and the cases they are wrong for

Video: A4 (316) Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips)

Third-party video, selected automatically for this topic. It is not produced by Engineering Hardware and is not a specification source — use the tables on this page for dimensional data.

Inside the plant

Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

01

Cold heading

Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail.

Head dimensions and under-head radius checked at set-up and per shift.
02

Thread rolling

Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch.

Go / no-go ring gauges to ISO 965 tolerance class 6g.
03

Heat treatment

Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it.

Core hardness and tensile tested per lot to ISO 898-1.
04

Surface treatment

Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list.

Coating thickness and neutral salt spray hours to ISO 9227.

Frequently Asked Questions

Should I choose A4 Stainless Steel or A2 (304) for Flat Head Machine Screws, UNC (Slotted and Phillips)?

For Flat Head Machine Screws, UNC (Slotted and Phillips), A4 Stainless Steel suits general indoor and outdoor use; A2 (304) is preferred for marine, coastal and chemical environments. Choose by corrosion exposure first.

Can A4 Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips) gall during installation?

Yes — stainless on stainless is prone to thread galling under load, especially at smaller sizes. Use an anti-galling lubricant or wax thread compound, and slow the tightening rate where possible.

Is A4 Stainless Steel food-grade?

A4 (316) is the standard food-contact stainless grade in most jurisdictions, particularly where chloride exposure (brines, dairy CIP) is present.

Can A4 Stainless Steel Flat Head Machine Screws, UNC (Slotted and Phillips) be used with aluminum?

Yes, but stainless drives mild galvanic corrosion of aluminum in wet service — isolate with a coating, sleeve or paint, or accept the trade-off if the joint is dry and indoor.

How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.

Why Choose A4 Stainless Steel for Flat Head Machine Screws, UNC (Slotted and Phillips)

Mechanical & Physical Properties

Galvanic & Galling Considerations

Comparable Grades

Using Stainless Fasteners in Aluminum

Sizes of Flat Head Machine Screws, UNC (Slotted and Phillips) Available in A4 Stainless Steel

Need this screw in a grade that is not listed?

Technical Drawing

Request a Quote

Request a Quotation

Dimensions & Specifications (ASME B18.6.3)

Materials & Grades

Stainless Steel

Austenitic Stainless Steel

Martensitic Stainless Steel

Ferritic Stainless Steel

Precipitation-Hardening Stainless Steel

Duplex and Super Duplex Stainless Steel

Carbon Steel

Low-Carbon Steel

Medium-Carbon Steel

High-Carbon Steel

Cold-Heading Steel