FIG. RESKnowledge hub

The fastener knowledge hub.

Selection guides, torque charts, thread identification, and material references — the same engineering data our team works from, free to use and built to be read like a datasheet.

Dataset index07

Fastener Selection GuideGuide
Bolt Torque Reference ChartChart
Thread & Size IdentificationReference
Material & Corrosion GuideGuide
Grade & Property Class MarkingsReference
Coatings & Finishes GuideGuide
Standards Cross-ReferenceReference

FIG. R0Index

Guides, charts, and references.

Seven datasets, each anchored below. Jump straight to the numbers or read the guides front to back.

Guide

Fastener Selection Guide

How to choose head style, drive, grade, material, and finish for a joint — matching clamp load, environment, and access to the right fastener family.

Open Chart

Bolt Torque Reference Chart

Recommended tightening torque in Nm and lb-ft for metric property classes 8.8, 10.9, and 12.9 across coarse-pitch sizes M5 to M24.

Open Reference

Thread & Size Identification

Major diameter, pitch or TPI, and tap-drill sizes for metric coarse, metric fine, UNC, and UNF threads — for identifying and tapping fasteners.

Open Guide

Material & Corrosion Guide

Density, corrosion resistance, strength, and typical use for carbon steel, 304 / 316 stainless, alloy steel, brass, and titanium.

Open Reference

Grade & Property Class Markings

Proof load, tensile strength, head markings, and material temper for SAE, ISO metric, ASTM, and stainless property classes.

Open Guide

Coatings & Finishes Guide

Zinc plating, hot-dip galvanizing, black oxide, and plain finishes — corrosion protection, salt-spray life, and where each belongs.

Open Reference

Standards Cross-Reference

Equivalence map across DIN, ISO, ASME / ANSI, ASTM, and SAE for the most common bolt, nut, and washer specifications.

Open

FIG. R1Guide · Selection

How to specify a fastener.

Six decisions take you from a joint to a part number. Work them in order — each one narrows the next.

STEP 01

Define the joint

Start with the load path — tension, shear, or both — plus grip length, tooling access, and how often it must come apart.

STEP 02

Choose family, head & drive

Hex for open wrenching, socket cap for high torque in tight space, countersunk for a flush face, flange to spread load without a washer.

STEP 03

Set the grade or class

Match the required proof load: 8.8 / Grade 5 for general work, 10.9–12.9 / Grade 8 for high-tensile joints, A2 / A4 where corrosion rules.

STEP 04

Select the material

Environment first — coated carbon steel indoors, 304 outdoors, 316 or titanium in salt and chloride, alloy steel where strength is the constraint.

STEP 05

Specify the finish

Balance corrosion life against galvanic compatibility: zinc indoors, hot-dip galvanizing for structural exterior, plain or oxide where sealed.

STEP 06

Confirm standard & locking

Pin the DIN / ISO / ASME number for dimensions, then add a prevailing-torque nut or thread-locker if the joint sees vibration or fatigue.

FIG. R2Chart · Torque

Bolt torque reference.

Recommended tightening torque for coarse-pitch steel bolts, property classes 8.8, 10.9, and 12.9. Each cell reads newton-metres then pound-feet.

Size	Pitch	Class 8.8	Class 10.9	Class 12.9
M5	0.8 mm	5.9 Nm · 4.4 lb-ft	8.6 Nm · 6.3 lb-ft	10 Nm · 7.4 lb-ft
M6	1 mm	10.1 Nm · 7.4 lb-ft	14.9 Nm · 11 lb-ft	17.4 Nm · 12.8 lb-ft
M8	1.25 mm	24.6 Nm · 18.1 lb-ft	36.1 Nm · 26.6 lb-ft	43.3 Nm · 31.9 lb-ft
M10	1.5 mm	48 Nm · 35.4 lb-ft	71 Nm · 52.4 lb-ft	85 Nm · 62.7 lb-ft
M12	1.75 mm	84 Nm · 62 lb-ft	123 Nm · 90.7 lb-ft	148 Nm · 109.2 lb-ft
M14	2 mm	133 Nm · 98.1 lb-ft	195 Nm · 143.8 lb-ft	234 Nm · 172.6 lb-ft
M16	2 mm	206 Nm · 151.9 lb-ft	302 Nm · 222.7 lb-ft	363 Nm · 267.7 lb-ft
M20	2.5 mm	415 Nm · 306.1 lb-ft	583 Nm · 429.9 lb-ft	700 Nm · 516.3 lb-ft
M24	3 mm	714 Nm · 526.6 lb-ft	1003 Nm · 739.8 lb-ft	1203 Nm · 887.3 lb-ft

Recommended tightening torque for coarse-pitch steel bolts at a friction coefficient µ ≈ 0.14 (lightly oiled), tensioned to roughly 90% of proof load. Verify against the joint's design preload, lubrication, and gasket.

FIG. R3Reference · Threads

Thread & size identification.

Major diameter, pitch or threads-per-inch, and recommended tap-drill size for the four common series. Tap drills target ≈ 75% thread engagement.

Metric Coarse

Size	Major Ø	Pitch / TPI	Tap drill (≈75%)
M3	3.00 mm	0.5 mm	2.5 mm
M4	4.00 mm	0.7 mm	3.3 mm
M5	5.00 mm	0.8 mm	4.2 mm
M6	6.00 mm	1 mm	5.0 mm
M8	8.00 mm	1.25 mm	6.8 mm
M10	10.00 mm	1.5 mm	8.5 mm
M12	12.00 mm	1.75 mm	10.2 mm
M16	16.00 mm	2 mm	14.0 mm
M20	20.00 mm	2.5 mm	17.5 mm
M24	24.00 mm	3 mm	21.0 mm
M30	30.00 mm	3.5 mm	26.5 mm
M36	36.00 mm	4 mm	32.0 mm

Metric Fine

Size	Major Ø	Pitch / TPI	Tap drill (≈75%)
M8 × 1.0	8.00 mm	1 mm	7.0 mm
M10 × 1.25	10.00 mm	1.25 mm	8.8 mm
M12 × 1.25	12.00 mm	1.25 mm	10.8 mm
M16 × 1.5	16.00 mm	1.5 mm	14.5 mm
M20 × 1.5	20.00 mm	1.5 mm	18.5 mm
M24 × 2.0	24.00 mm	2 mm	22.0 mm

UNC

Size	Major Ø	Pitch / TPI	Tap drill (≈75%)
#4-40	2.84 mm	40 TPI	#43 (2.26 mm)
#6-32	3.51 mm	32 TPI	#36 (2.71 mm)
#8-32	4.17 mm	32 TPI	#29 (3.45 mm)
#10-24	4.83 mm	24 TPI	#25 (3.80 mm)
1/4"-20	6.35 mm	20 TPI	#7 (5.11 mm)
5/16"-18	7.94 mm	18 TPI	F (6.53 mm)
3/8"-16	9.53 mm	16 TPI	5/16" (7.94 mm)
1/2"-13	12.70 mm	13 TPI	27/64" (10.72 mm)
5/8"-11	15.88 mm	11 TPI	17/32" (13.49 mm)
3/4"-10	19.05 mm	10 TPI	21/32" (16.67 mm)
1"-8	25.40 mm	8 TPI	7/8" (22.23 mm)

UNF

Size	Major Ø	Pitch / TPI	Tap drill (≈75%)
#10-32	4.83 mm	32 TPI	#21 (4.04 mm)
1/4"-28	6.35 mm	28 TPI	#3 (5.41 mm)
5/16"-24	7.94 mm	24 TPI	I (6.91 mm)
3/8"-24	9.53 mm	24 TPI	Q (8.43 mm)
1/2"-20	12.70 mm	20 TPI	29/64" (11.51 mm)
3/4"-16	19.05 mm	16 TPI	11/16" (17.46 mm)

FIG. R4Guide · Materials

Material & corrosion guide.

Density, corrosion behaviour, strength, and where each material belongs — carbon steel through titanium.

Material	Density	Corrosion	Strength	Typical use
Carbon Steel	7.85 g/cm³	Low — requires zinc, galvanized, or oxide coating	Heat-treatable; classes 4.6–8.8 / SAE 2–5 (up to ~830 MPa)	General structural, machine, and construction fastening
Stainless 304	8.00 g/cm³	Good — resists atmospheric and mild chemical attack; non-magnetic	Austenitic, work-hardening; A2-70 ≈ 700 MPa tensile	Food, architectural, and general outdoor hardware
Stainless 316	8.00 g/cm³	Excellent — 2–3% molybdenum resists chlorides, salt, and pitting	Austenitic; A4-80 ≈ 800 MPa tensile	Marine, coastal, and chemical-process fastening
Alloy Steel	7.85 g/cm³	Low — must be plated or oxide-coated	Quenched & tempered; classes 10.9 / 12.9 / SAE 8 (1040–1220 MPa)	High-tensile socket screws and safety-critical joints
Brass	8.50 g/cm³	Good — non-sparking, non-magnetic, develops decorative patina	CW614N / C36000; ~340–470 MPa tensile, free-machining	Electrical, plumbing, and decorative applications
Titanium	4.43 g/cm³	Excellent — passive oxide film, seawater and acid resistant	Ti-6Al-4V (Gr 5) ≈ 900–1100 MPa; ~45% lighter than steel	Aerospace, marine, and weight-critical structures

FIG. R5Reference · Grades

Grade & property-class markings.

Proof load, ultimate tensile, head marking, and material temper across the metric, SAE, ASTM, and stainless systems.

Grade	System	Proof load	Tensile	Head marking	Material
Class 4.6	Metric	225 MPa	400 MPa	Head marked '4.6'	Low/medium carbon steel
Class 8.8	Metric	580–600 MPa	800 MPa	Head marked '8.8'	Medium carbon steel, quenched & tempered
Class 10.9	Metric	830 MPa	1040 MPa	Head marked '10.9'	Alloy steel, quenched & tempered
Class 12.9	Metric	970 MPa	1220 MPa	Head marked '12.9'	Alloy steel, quenched & tempered
SAE Grade 2	SAE	55 ksi	74 ksi	No head markings (plain)	Low/medium carbon steel
SAE Grade 5	SAE	85 ksi	120 ksi	Three radial lines	Medium carbon steel, quenched & tempered
SAE Grade 8	SAE	120 ksi	150 ksi	Six radial lines	Medium carbon alloy steel, Q&T
ASTM A325	ASTM	85 ksi (≤1")	120 ksi	Marked 'A325' + maker	Structural medium carbon steel
ASTM A490	ASTM	120 ksi	150–173 ksi	Marked 'A490' + maker	Structural alloy steel
ASTM A193 B7	ASTM	105 ksi (0.2% yield)	125 ksi	Marked 'B7'	Chromium-moly alloy (AISI 4140)
A2-70 (304)	Stainless	450 MPa (0.2% proof)	700 MPa	Marked 'A2-70'	Austenitic 304, cold worked
A4-80 (316)	Stainless	600 MPa (0.2% proof)	800 MPa	Marked 'A4-80'	Austenitic 316, cold worked

FIG. R6Guide · Finishes

Coatings & finishes.

What each finish is, how much corrosion protection it buys, and where it belongs. When in doubt, match the finish to the environment, not the budget.

Finish	Process	Salt-spray / life	Best for
Zinc Plated	Electroplated zinc, 5–25 µm, with clear, yellow, or black passivate	≈ 12–96 h to white rust (ASTM B117)	Indoor and light-outdoor general-purpose corrosion protection
Hot-Dip Galvanized	Molten-zinc immersion, 45–85 µm, to ASTM A153	1,000+ h salt spray; decades in the open	Structural steel, exterior, and coastal-adjacent exposure
Black Oxide	Alkaline conversion coating sealed with oil	Minimal without oil — mild indoor service only	Tooling, fixtures, and low-glare cosmetic finishes
Plain	As-forged or as-machined, lightly oiled	None — relies on a sealed or dry environment	Sealed assemblies, oiled service, or pre-paint stock

FIG. R7Reference · Standards

Standards cross-reference.

The most common bolt, nut, and washer specifications mapped across DIN, ISO, and ASME / ANSI — for converting a callout from one system to another.

Component	DIN	ISO	ASME / ANSI	Note
Hex head bolt / setscrew	DIN 931 / 933	ISO 4014 / 4017	ASME B18.2.1	Partial vs full thread
Hex nut	DIN 934	ISO 4032	ASME B18.2.2	Style 1
Socket head cap screw	DIN 912	ISO 4762	ASME B18.3	Hex (Allen) drive
Countersunk socket screw	DIN 7991	ISO 10642	—	Flat head
Flat washer	DIN 125	ISO 7089	ASME B18.22.1	≈ 200 HV
Spring lock washer	DIN 127	—	ASME B18.21.1	Split helical
Hex flange bolt	DIN 6921	ISO 4162	—	Serrated flange
Nylon-insert lock nut	DIN 985	ISO 10511	—	Prevailing torque

Equivalents are dimensional best-matches, not drop-in substitutions — always confirm tolerance class, property class, and any code requirement before swapping a specification.

FIG. CTAEngineering desk

Need a spec we don't list?

If you can't find the size, grade, or standard here, our engineers can. Send the requirement and we'll cross-reference it against the catalog.

Ask an engineer Browse the catalog