Hex Cap Screws Manufacturer in India | Grade 5 & 8 Hex Head Cap Screws

Overview

Grade 5 & 8 Hex Head Cap Screws & ISO 4017 Hex Screws: Manufacturer & Exporter

A hex cap screw is the finished hexagon head screw of ASME B18.2.1. It has a washer face under the head, tight head and body tolerances, and a chamfered point. It is turned by its head into a tapped hole or a nut, and is the standard hex fastener for machinery, vehicles and equipment.

Exotic Alloy manufactures hex cap screws in Mumbai, India, for OEMs, machine builders, pump and valve makers, and maintenance stores. We supply across India and export to Brazil, the USA, the Gulf and Africa. Heads are cold or hot forged and trimmed, threads are rolled, and Grade 5 and 8 lots are quenched, tempered and proof-load tested.

Cap screw or bolt?

If it goes into a tapped hole, or its head is turned to tighten it, you need a cap screw. A hex bolt is the cheaper unfinished part intended for use with a nut. See hex bolts for the full metric bolt range.

ASME B18.2.1 SAE Grade 2 / 5 / 8 UNC & UNF ISO 4017 / DIN 933 Zinc, yellow zinc, plain

Hex cap screw at a glance

Head: Hex with washer face, F ≈ 1.5 D
Point: Chamfered
Thread: UNC / UNF class 2A; 2D + ¼″
Grades: SAE J429 Gr 2, 5, 8; A449; stainless
Metric: ISO 4017 / 4014, DIN 933 / 931
Related: Hex bolts, socket cap screws, flange bolts

½-13 × 2 hex cap screw to ASME B18.2.1, drawn to scale (top view at 125 %, washer face thickness exaggerated). The washer face is a thin raised ring under the head, 90 to 100 % of the across-flats width and 0.015 to 0.025″ thick on sizes to ¾″.

Specification

Hex Cap Screw Specification

The range we manufacture and supply.

StandardsASME B18.2.1 hex cap screws; SAE J429; ASTM A449; ASTM F593 stainless; ISO 4017, ISO 4014, DIN 933, DIN 931

Size range¼″ to 1½″ (larger to order); M3 to M36; lengths ½″ to 12″ and 6 to 300 mm

ThreadUNC, UNF and 8-UN, class 2A; metric coarse and fine, 6g; full thread (ISO 4017) or part thread

GradesSAE Grade 2, 5, 8; ASTM A449; 8.8, 10.9, 12.9; A2-70, A4-70, A4-80

MaterialsLow and medium carbon steel, boron steel, Cr-Mo alloy steel, stainless 304 / 316

FinishPlain; clear or yellow zinc; zinc flake; hot-dip galvanized (with over-tapped nuts); passivated stainless

HeadHex with washer face; drilled head or shank for lock wire on request

MarkingSAE grade lines or property class plus maker’s mark

CertificationMill certificate; EN 10204 3.1 with hardness, proof load and dimensions

PackingBoxes, bulk cartons, kits with nuts and washers

Cap screw vs bolt

Hex Cap Screw vs Hex Bolt

They look alike, but ASME treats them as different products.

How each is used (sections, schematic). A cap screw is tightened by its head and often threads straight into the part. A bolt is held at the head while its nut is tightened.

Feature	Hex cap screw	Hex bolt
ASME B18.2.1	Finished hex head screw	Unfinished hex bolt
Under the head	Washer face	Plain bearing face
Tolerances	Close: head, body and length	Wider
Point	Chamfered	Plain cut or chamfered
Use	Tapped holes or nuts; turned by the head	With a nut; nut turned
Usual grades	SAE Grade 5, Grade 8, A449	ASTM A307 Grade A
Metric equivalent	ISO 4014 / 4017, grade A / B	ISO 4016 / 4018, grade C

Dimensions

Hex Cap Screw Dimensions: ASME B18.2.1 & ISO 4017

Size	Body d_s max / min	Across flats s max / min	Across corners e max / min	Head height k max / min	Wrenching height k_w min	Thread b L ≤ 6″ / > 6″
1/4″-20	0.250 / 0.245	0.438 / 0.428	0.505 / 0.488	0.163 / 0.150	0.106	0.75 / 1
5/16″-18	0.3125 / 0.3065	0.500 / 0.489	0.577 / 0.557	0.211 / 0.195	0.140	0.875 / 1.125
3/8″-16	0.375 / 0.369	0.562 / 0.551	0.650 / 0.628	0.243 / 0.226	0.160	1 / 1.25
7/16″-14	0.4375 / 0.4305	0.625 / 0.612	0.722 / 0.698	0.291 / 0.272	0.195	1.125 / 1.375
1/2″-13	0.500 / 0.493	0.750 / 0.736	0.866 / 0.840	0.323 / 0.302	0.215	1.25 / 1.5
9/16″-12	0.5625 / 0.5545	0.812 / 0.798	0.938 / 0.910	0.371 / 0.348	0.250	1.375 / 1.625
5/8″-11	0.625 / 0.617	0.938 / 0.922	1.083 / 1.051	0.403 / 0.378	0.269	1.5 / 1.75
3/4″-10	0.750 / 0.741	1.125 / 1.100	1.299 / 1.254	0.483 / 0.455	0.324	1.75 / 2
7/8″-9	0.875 / 0.866	1.312 / 1.285	1.516 / 1.465	0.563 / 0.531	0.378	2 / 2.25
1″-8	1.000 / 0.990	1.500 / 1.469	1.732 / 1.675	0.627 / 0.591	0.416	2.25 / 2.5
1-1/8″-7	1.125 / 1.114	1.688 / 1.631	1.949 / 1.859	0.718 / 0.658	0.461	2.5 / 2.75
1-1/4″-7	1.250 / 1.239	1.875 / 1.812	2.165 / 2.066	0.813 / 0.749	0.530	2.75 / 3
1-3/8″-6	1.375 / 1.363	2.062 / 1.994	2.382 / 2.273	0.878 / 0.810	0.569	3 / 3.25
1-1/2″-6	1.500 / 1.488	2.250 / 2.175	2.598 / 2.480	0.974 / 0.902	0.640	3.25 / 3.5

ASME B18.2.1-2012 Table 6, hex cap screws, inches; UNF threads use the same heads. We checked every row: e max = s max / cos 30° and b = 2D + ¼″. Washer face: diameter s max −10 %, thickness 0.015 to 0.025″ (¾″ and below) or 0.015 to 0.035″ (larger).

Size	Pitch P	s across flats	e min grade A / B	k nominal	k min grade A / B	DIN 933 s if different
M3	0.5	5.5	6.01 / 5.88	2	1.875 / 1.8	—
M4	0.7	7	7.66 / 7.5	2.8	2.675 / 2.6	—
M5	0.8	8	8.79 / 8.63	3.5	3.35 / 3.26	—
M6	1	10	11.05 / 10.89	4	3.85 / 3.76	—
M8	1.25	13	14.38 / 14.2	5.3	5.15 / 5.06	—
M10	1.5	16	17.77 / 17.59	6.4	6.22 / 6.11	17
M12	1.75	18	20.03 / 19.85	7.5	7.32 / 7.21	19
M14	2	21	23.36 / 22.78	8.8	8.62 / 8.51	22
M16	2	24	26.75 / 26.17	10	9.82 / 9.71	—
M18	2.5	27	30.14 / 29.56	11.5	11.285 / 11.15	—
M20	2.5	30	33.53 / 32.85	12.5	12.285 / 12.15	—
M22	2.5	34	37.72 / 37.29	14	13.785 / 13.65	32
M24	3	36	39.98 / 39.55	15	14.785 / 14.65	—

DIN EN ISO 4017:2014, fully threaded hex head screws, mm. Product grade A for d ≤ M24 and l ≤ 10 d or 150 mm; grade B above. Four sizes have different head widths in DIN 933.

Grades

Hex Cap Screw Grades, Markings & Proof Loads

Head markings (schematic). The radial lines show the SAE grade; metric screws carry the class in figures.

Grade	Size	Proof stress	Yield min	Tensile min	Hardness	Head marking
SAE J429 Grade 2	¼ – ¾″	55 ksi	57 ksi	74 ksi	B80–B100	None
SAE J429 Grade 2	⅝ – 1½″	33 ksi	36 ksi	60 ksi	B70–B100	None
SAE J429 Grade 5	¼ – 1″	85 ksi	92 ksi	120 ksi	C25–C34	3 radial lines
SAE J429 Grade 5	1⅛ – 1½″	74 ksi	81 ksi	105 ksi	C19–C30	3 radial lines
SAE J429 Grade 8	¼ – 1½″	120 ksi	130 ksi	150 ksi	C33–C39	6 radial lines
ASTM A449 Type 1	¼ – 1″	85 ksi	92 ksi	120 ksi	C25–C34	Per ASTM A449
ISO 898-1 class 8.8	≤ M16 / > M16	580 / 600 MPa	640 / 660 MPa	800 / 830 MPa	22–32 / 23–34 HRC	8.8
ISO 898-1 class 10.9	all	830 MPa	940 MPa	1040 MPa	32–39 HRC	10.9
ISO 3506-1 A2-70 / A4-70	≤ M24	—	450 MPa	700 MPa	—	A2-70 / A4-70

Proof and tensile loads, UNC

Size	Stress area A_s in²	Grade 2 proof lbf	Grade 5 proof lbf	Grade 5 tensile lbf	Grade 8 proof lbf	Grade 8 tensile lbf
1/4″-20	0.0318	1,750	2,700	3,820	3,820	4,770
5/16″-18	0.0524	2,880	4,460	6,290	6,290	7,860
3/8″-16	0.0775	4,260	6,590	9,300	9,300	11,620
7/16″-14	0.1063	5,850	9,040	12,760	12,760	15,950
1/2″-13	0.1419	7,800	12,060	17,030	17,030	21,280
9/16″-12	0.1819	10,010	15,470	21,830	21,830	27,290
5/8″-11	0.2260	12,430	19,210	27,120	27,120	33,900
3/4″-10	0.3345	18,400	28,430	40,140	40,140	50,170
7/8″-9	0.4617	15,240	39,250	55,410	55,410	69,260
1″-8	0.6057	19,990	51,490	72,690	72,690	90,860
1-1/8″-7	0.7633	25,190	56,480	80,140	91,590	114,490
1-1/4″-7	0.9691	31,980	71,710	101,760	116,290	145,370
1-3/8″-6	1.1549	38,110	85,460	121,260	138,590	173,230
1-1/2″-6	1.4053	46,370	103,990	147,550	168,630	210,790

Our calculation: load = A_s × stress, with A_s = 0.7854 (D − 0.9743 / n)². Grade 2 proof is 55 ksi to ¾″ and 33 ksi above; Grade 5 is 85 / 120 ksi to 1″ and 74 / 105 ksi above.

Thread engagement

Cap Screws in Tapped Holes: How Deep to Thread

A cap screw in a tapped hole should break before its threads strip. The softer the tapped material, the longer the engagement it needs.

Left: an M10 screw in a tapped hole (section). Right: minimum engagement for an M10 class 8.8 screw, by the shear-area method with basic thread dimensions (our calculation).

Minimum engagement by size and material

Size	Tap drill	8.8 in S235 steel	8.8 in ductile iron	8.8 in 6061-T6 aluminium	10.9 in S235 steel
M3	2.5 mm	2.7 mm (0.90 d)	2.4 mm (0.81 d)	3.8 mm (1.25 d)	3.5 mm (1.17 d)
M4	3.3 mm	3.5 mm (0.89 d)	3.2 mm (0.80 d)	4.9 mm (1.23 d)	4.6 mm (1.15 d)
M5	4.2 mm	4.6 mm (0.92 d)	4.1 mm (0.83 d)	6.4 mm (1.27 d)	6.0 mm (1.19 d)
M6	5 mm	5.4 mm (0.90 d)	4.9 mm (0.81 d)	7.5 mm (1.25 d)	7.0 mm (1.17 d)
M8	6.75 mm	7.4 mm (0.92 d)	6.7 mm (0.83 d)	10.2 mm (1.28 d)	9.6 mm (1.20 d)
M10	8.5 mm	9.4 mm (0.94 d)	8.4 mm (0.84 d)	13.0 mm (1.30 d)	12.2 mm (1.22 d)
M12	10.25 mm	11.4 mm (0.95 d)	10.2 mm (0.85 d)	15.7 mm (1.31 d)	14.8 mm (1.23 d)
M14	12 mm	13.3 mm (0.95 d)	12.0 mm (0.85 d)	18.4 mm (1.31 d)	17.3 mm (1.23 d)
M16	14 mm	15.9 mm (0.99 d)	14.3 mm (0.89 d)	22.0 mm (1.37 d)	20.6 mm (1.29 d)
M20	17.5 mm	20.5 mm (1.03 d)	18.5 mm (0.92 d)	28.5 mm (1.42 d)	25.7 mm (1.29 d)
M24	21 mm	24.7 mm (1.03 d)	22.2 mm (0.93 d)	34.2 mm (1.42 d)	30.9 mm (1.29 d)
M30	26.5 mm	31.4 mm (1.05 d)	28.2 mm (0.94 d)	43.4 mm (1.45 d)	39.3 mm (1.31 d)
M36	32 mm	38.1 mm (1.06 d)	34.3 mm (0.95 d)	52.7 mm (1.46 d)	47.7 mm (1.33 d)

Our calculation, Machinery’s Handbook method: external thread shear area ≈ 0.75 π D₁ per unit length, internal ≈ 0.875 π d, shear strength = 0.5 × tensile. Basic dimensions only. Real thread tolerances reduce the shear area, so allow a margin above these minimums. Grey cast iron is not covered by this method.

Calculator

Thread Engagement Calculator for Tapped Holes

Choose the screw, its grade and the material of the tapped part to get the minimum engagement, which thread would strip first, and the tap drill.

Screw & tapped part

System

Size

Screw grade

Tapped material

Material strengths are minimum tensile values. Basic thread dimensions, no tolerances: allow a margin above the result for production threads.

Minimum engagement

9.4

mm engaged

0.94

× diameter d

Screw thread strips at:5.9 mm

Tapped thread strips at:9.4 mm

Tap drill:8.5 mm

Materials & finishes

Hex Cap Screw Materials & Finishes

Every grade links to its datasheet on this site.

Low / medium carbon

Grade 2 · Grade 5

Grade 5 is medium carbon steel, quenched and tempered.

1018 1035

Alloy & boron steel

Grade 8 · 10.9

Medium carbon alloy or boron steel, hardened to C33–C39.

15B35H 4140

Stainless A2

304 · A2-70

The grade in the photo: general corrosion resistance.

304 304L

Stainless A4

316 · A4-70 / 80

Marine, chemical and food equipment.

316 316L

Finish	Specification	Notes
Clear zinc	ASTM F1941 / ISO 4042	Indoor machinery; Grade 8 plated lots baked against hydrogen embrittlement
Yellow zinc	ASTM F1941	Traditional finish for Grade 8 in the US market
Zinc flake	ASTM F1136 / ISO 10683	High corrosion resistance, no hydrogen risk
Hot-dip galvanized	ASTM F2329	Outdoor; nuts are over-tapped
Passivated stainless	ASTM A967	A2 / A4 screws

Manufacturing

How Our Hex Cap Screws Are Made

1

Wire

Spheroidize-annealed carbon, boron, alloy or stainless wire, certified by heat.

2

Heading & trimming

Head and washer face upset, then the hex trimmed to size.

3

Pointing & rolling

Chamfered point formed and UNC / UNF threads rolled.

4

Heat treatment

Grade 5 and 8 quenched and tempered in continuous furnaces.

5

Finishing

Zinc, yellow zinc, zinc flake or passivation, with baking where needed.

6

Testing

Hardness, proof load and wedge tensile per lot.

Applications

Where Our Hex Cap Screws Are Used

Machinery & gearboxes

Housings, covers and mounts tapped straight into castings.

Trucks & equipment

Grade 8 screws on frames, axles and hitches.

Pumps & valves

Bonnet and casing screws in Grade 5, 8 and stainless.

Agriculture & construction

Implements, buckets and wear parts.

Electrical & HVAC

Motor bases, switchgear and air-handling units.

MRO stores

Boxed Grade 5 and 8 assortments for maintenance teams.

Quality & testing

Hex Cap Screw Testing & Certification

Check	Method	Applied to
Head & body	Callipers and micrometers against Table 6 limits	Every lot
Thread	2A ring gauges (after coating)	Every lot
Hardness	Rockwell, surface and core	Every heat-treatment lot
Proof load & wedge tensile	ASTM F606 / ISO 898-1	Grade 5, 8, A449, 8.8, 10.9
Decarburization	Microsection per SAE J121	Grade 5 and 8
Coating	Thickness and salt spray	Plated lots

Every shipment includes

Mill certificate with heat number
Hardness and dimensional report
Lot traceability on every box

On request

EN 10204 3.1 certificate
Proof load and wedge tensile report
Dimensional layout report

FAQ

Hex Cap Screw Questions, Answered

A hex cap screw is a hexagon head screw made to ASME B18.2.1 with a washer face under the head, closer head tolerances than a hex bolt and a chamfered point. It is tightened by its head, either into a tapped hole or with a nut. The metric equivalents are ISO 4014 and ISO 4017 (DIN 931 and DIN 933) hex head bolts and screws in product grades A and B.

In ASME B18.2.1 a hex bolt is an unfinished part with a plain bearing face and wider tolerances, intended to be used with a nut. A hex cap screw is finished: it has a washer face, tighter head and body tolerances and a chamfered point, so it can be threaded into a tapped hole as well as used with a nut. Hex cap screws are the usual choice for machinery.

The radial lines show the SAE J429 grade: no lines for Grade 2, three lines for Grade 5 and six lines for Grade 8. Metric screws show the ISO 898-1 property class, such as 8.8 or 10.9, and stainless screws show A2-70 or A4-70. A maker's mark appears on the head as well.

A 1/2 inch hex cap screw is 3/4 inch across flats, so it takes a 3/4 inch wrench. Other common sizes are 9/16 inch for 3/8 inch screws, 15/16 inch for 5/8 inch and 1-1/8 inch for 3/4 inch. Metric M10 screws take 16 mm to ISO 4017, but 17 mm to the older DIN 933.

Enough for the screw to break before the threads strip. By the basic-dimension shear-area method, an M10 class 8.8 screw needs about 0.94 d of engagement in S235 steel and about 1.3 d in 6061-T6 aluminium. Thread tolerances reduce the shear area, which is why the practical rules of about 1 d in steel and 2 d in aluminium include a margin. The calculator on this page works it out for each size and material.

ASME B18.2.1 gives a reference thread length of twice the diameter plus 1/4 inch for screws up to 6 inches long, and twice the diameter plus 1/2 inch for longer screws. A 1/2 x 2 inch cap screw therefore has 1.25 inches of thread. Shorter screws are threaded close to the head.

Grade 8 has a minimum tensile strength of 150,000 psi against 120,000 psi for Grade 5 (up to 1 inch), and a proof stress of 120,000 psi against 85,000 psi. For a 1/2-13 screw that is a proof load of about 17,030 lbf for Grade 8 and 12,060 lbf for Grade 5. Grade 8 is harder, Rockwell C33 to C39.

They are the same fully threaded hex head screw, except that ISO 4017 uses smaller heads in four sizes: M10 is 16 mm across flats instead of 17 mm, M12 18 instead of 19, M14 21 instead of 22, and M22 34 instead of 32. Check which width your spanners and drawings expect.