Bolts · Hex Bolts

Hex Head Cap Screws, UNC

23 catalogued sizes, dimensioned to ASME B18.2.1. Pick any row and the technical drawing redraws to it.

Hex Head Cap Screws, UNC to ASME B18.2.1 are catalogued in pitch 1.27-6.35 mm, with wide 12.83-175.98 mm, head h 4.37-68.26 mm, spanner 11.11-152.4 mm. 23 sizes are held in the table below, and the technical drawing redraws to whichever row you select.

Standard: ASME B18.2.1
Pitch: 1.27-6.35 mm
Wide: 12.83-175.98 mm
Head H: 4.37-68.26 mm
Catalogued sizes: 23

Dimensions are nominal values from the governing standard. Confirm the tolerance class for your application before ordering.

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

Where Hex Head Cap Screws are used, and what decides the specification in each case. Stocked from 1/4" to 4" (screw size).

Industries that specify Hex Head Cap Screws

Heavy equipment US-built machinery.
Automotive inch fasteners on US vehicles.
Agricultural equipment North American machinery.
Industrial maintenance inch repairs.
Maintenance & MRO Stocked replacements matched to an existing property class, thread and finish.
Food, pharma & cleanroom Stainless assemblies that are washed down, where the finish matters as much as the strength.

Typical applications

matching US equipment
inch threads
general machine bolting
high-strength grades
clamping two machined faces to a calculated preload
bolting brackets, motors and gearboxes to a frame

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 mix inch and metric bolts; 5/16" and M8 are close but do not interchange.
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 Hex Head Cap Screws are used, how to specify them, and the cases they are wrong for

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 1/4" Hex Head Cap Screws, UNC to ASME B18.2.1. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

b (mm): 19.05
Pitch P (mm): 1.27
c (mm): 0.406
dw (mm): 10.557
Width across corners e (mm): 12.832
Head height k (mm): 4.366
r (mm): 0.37
Width across flats s (mm): 11.113
Length range l (in): 3/8"~12"

Sends the selected values to the quote form below.

Request a Quotation for Hex Head Cap Screws, UNC

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

Request a Quotation

Specification

Item / category Standard Size(s) Material / finish Quantity

Business Information

Company * Contact Name * Email * Phone (with country code) Country / Region

Notes

Dimensions & Specifications (ASME B18.2.1)

Every row below is a starting point for the customizer above — pick any size and the drawing will redraw to that row.

Size	b (mm)	Pitch P (mm)	c (mm)	dw (mm)	Width across corners e (mm)	Head height k (mm)	r (mm)	Width across flats s (mm)	Length range l (in)	Reference standard
1/4"	19.05	1.27	0.406	10.557	12.832	4.366	0.37	11.113	3/8"~12"	ASME B18.2.1
5/16"	22.225	1.411	0.406	12.065	14.665	5.556	0.423	12.7	1/2"~12"	ASME B18.2.1
3/8"	25.4	1.587	0.406	13.573	16.498	6.35	0.476	14.287	1/2"~12"	ASME B18.2.1
7/16"	28.575	1.814	0.406	15.081	18.331	7.541	0.529	15.875	3/4"~12"	ASME B18.2.1
1/2"	31.75	1.954	0.406	18.098	21.997	8.731	0.635	19.05	3/4"~12"	ASME B18.2.1
5/8"	38.1	2.309	0.406	22.622	27.496	10.716	0.794	23.812	3/4"~14"	ASME B18.2.1
3/4"	44.45	2.54	0.406	27.146	32.996	12.7	0.953	28.575	1"~14"	ASME B18.2.1
7/8"	50.8	2.822	0.406	31.671	38.495	14.684	1.111	33.337	1 1/2"~14"	ASME B18.2.1
1"	57.15	3.175	0.406	36.195	43.994	17.066	1.27	38.1	1 1/2"~14"	ASME B18.2.1
1 1/8"	63.5	3.629	0.406	40.719	49.493	19.05	1.429	42.862	1 5/8"~14"	ASME B18.2.1
1 1/4"	69.85	3.629	0.406	45.244	54.993	21.431	1.587	47.625	1 5/8"~14"	ASME B18.2.1
1 3/8"	76.2	4.233	0.406	49.768	60.492	23.019	1.746	52.388	1 3/4"~14"	ASME B18.2.1
1 1/2"	82.55	4.233	0.406	54.292	65.991	25.4	1.905	57.15	1 3/4"~14"	ASME B18.2.1
1 3/4"	95.25	5.08	0.406	63.341	76.99	29.369	2.223	66.675	2"~14"	ASME B18.2.1
2"	107.95	5.644	0.406	72.39	87.988	34.131	2.54	76.2	2 1/2"~14"	ASME B18.2.1
2 1/4"	120.65	5.644	0.406	81.439	98.987	38.1	2.857	85.725	2 1/2"~14"	ASME B18.2.1
2 1/2"	133.35	6.35	0.406	90.487	109.985	42.069	3.175	95.25	3"~14"	ASME B18.2.1
2 3/4"	146.05	6.35	0.406	99.536	120.984	46.038	3.493	104.775	3"~14"	ASME B18.2.1
3"	158.75	6.35	0.406	108.585	131.982	50.8	3.81	114.3	3 1/2"~14"	ASME B18.2.1
3 1/4"	171.45	6.35	0.406	117.634	142.981	55.562	4.128	123.825	3 3/4"~14"	ASME B18.2.1
3 1/2"	184.15	6.35	0.406	126.683	153.979	58.737	4.445	133.35	3 3/4"~14"	ASME B18.2.1
3 3/4"	196.85	6.35	0.406	135.731	164.978	63.5	4.763	142.875	4"~14"	ASME B18.2.1
4"	209.55	6.35	0.406	144.78	175.976	68.263	5.08	152.4	4"~14"	ASME B18.2.1

Manufactured to ASME B18.2.1, Hex Head Cap Screws, UNC are bolts supplied by Engineering Hardware. The dimensional data, materials and selection notes are summarized here.

What Are Hex Head Cap Screws, UNC?

Hex Head Cap Screws, UNC are bolts defined by ASME B18.2.1. They are selected by screw size and the dimensional characteristics shown below, and are available in a range of materials and finishes to suit the application and environment.

Materials & Finishes

Common materials include carbon steel (typically zinc plated or hot-dip galvanized), alloy steel in property classes 8.8, 10.9 and 12.9, and stainless steel A2 (304) or A4 (316) for corrosion resistance. Specify the material, property class and surface finish appropriate to your load and environment.

Specification Guides

Each size, material and standard of Hex Head Cap Screws, UNC has its own reference page with the figures for that one configuration.

Goes With

Hardware commonly specified alongside Hex Head Cap Screws, UNC.

Pricing

Hex Head Cap Screws, UNC are supplied to order. Pricing starts from approximately US$0.10 per piece for standard sizes in carbon steel; final pricing depends on size, material, finish and order quantity (MOQ applies). Submit your exact configuration with the quote form above.

Custom manufacturing · Made to drawing

Need a hex head cap screws, UNC outside the standard range?

Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or hot forging.

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

Custom bolt manufacturing Send a drawing

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

What is the controlling standard for Hex Head Cap Screws, UNC, and what drive do they take?

Hex Head Cap Screws, UNC are manufactured to ASME B18.2.1 and use an external hex drive. The dimensional values on this page follow that standard.

Which sizes of Hex Head Cap Screws, UNC does Engineering Hardware supply?

The table on this page lists 23 sizes for Hex Head Cap Screws, UNC, ranging from 1/4" to 4". Sizes outside the table can be quoted on request.

In which materials are Hex Head Cap Screws, UNC supplied?

Hex Head Cap Screws, UNC are supplied in carbon steel in property classes 8.8 / 10.9 / 12.9 and stainless A2 (304) / A4 (316), with finishes including zinc plating, hot-dip galvanizing and black oxide. Choose material and finish to suit the load and the service environment for Hex Head Cap Screws, UNC.

What spanner sizes do Hex Head Cap Screws, UNC take?

The width-across-flats for the smallest size on this page is 11.113 mm; the full table opposite the drawing lists the spanner size for every Hex Head Cap Screws, UNC.

How do I request a quotation?

Use the parametric drawing on this page to set the exact configuration (size, material, finish) and click "Request this configuration" — a specialist from Engineering Hardware will respond within one business day.

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