What is the difference between metric and standard fasteners?

Read time: 30 minutes | Updated on: 21 November 2023

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Depending on the context, “standard” often refers to U.S. fasteners. This typically means we’re talking about an imperial measurement system, measuring units in inches, whereas metric uses the decimal based system and measurements are based on metric units, such as millimeters. Keep in mind, however, the U.S. is now producing fasteners using the metric system.

The other definition of standard is the set of specifications as defined by organizations. In this article, we'll cover the differences between the metric and standard systems, the different units used and a metric to imperial conversion chart. We'll also cover:

Standard and metric systems

The major difference between metric and standard systems is in how threads are specified. Standard fasteners are either Unified National Coarse Thread (UNC) or Unified National Fine Thread (UNT). Standard metric threads, meaning ISO metric threads in this case, are not specified this way, though they are comparable to UNC threads.

Another difference between these imperial and metric systems is their system of measurement. The metric system for measuring screw threads uses metric units, pitch in millimeters (mm). This is the distance measured between the peaks of two adjacent threads. Whereas, the standard system - the imperial system - measures threads in imperial units by TPI: threads per inch. You literally just count the number of threads that cover a one-inch distance.

Learn more about screw threads in our guide, What are screw thread sizes?

Metric screw sizes vs standard system

These two systems for metric and standard sizes are communicated differently. Standard metric screw dimensions are determined by the pitch and the major diameter, which as the illustration shows, is the largest diameter of the screw.

Let's say it's 4mm, in which case it appears as M4 (the M means metric). Now let's say the pitch is 1mm. The size of your screw is M4 x 1mm.

Let's consider standard bolt sizes. For fasteners measured in inches, take the nominal major diameter and the threads per inch. For example, a 5/8-11 (coarse) thread means the nominal major diameter is 5/8"and the 11 means 11 threads per inch.

Understand how to measure bolt sizes in our expert guide.

Metric vs standard chart

Metric or standard? Here’s how they compare:

Inches		Metric Size- Pitch, ISO and IFI Rec.
(UNC)	(UNF)
1- 64	1- 72	M2 x 0.4
3- 48	3- 56	M2.5 x 0.45
4- 40	4- 48	M3 x 0.5
6- 32	6- 40	M3.5 x 0.6
8- 32	8- 36	M4 x 0.7
10- 24	10- 32	M5 x 0.8
1/4- 20	1/4- 28	M 6x 1
5/16-18	5/16- 24	M8 x 1.25
3/8-16	3/8- 24	M10 x 1.5
7/16-14	7/16- 20	M12 x 1.75
1/2- 13	1/2- 20	M14 x 2
5/8- 11	5/8- 18	M18 x 2
3/4- 10	3/4- 16	M20 x 2.5
1- 8	1-12	M24 x 3
1-1/4- 7	1-1/8- 12	M30 x 3.5
1-1/2- 6	1-1/4- 12	M36 x 4

Get expert advice

If you have any questions about metric and standard fastener sizing, speak to our experts.

Phone: +1 800 847 0486

Email: sales@essentracomponents.com

Fastener standards organizations

Standards are necessary to enable us to specify, test and assess fasteners’ properties. These are the organizations we’re covering in this article:

ASTM International: Formerly known as the American Society for Testing and Materials, and informally called ASTM. They are a worldwide recognized leader in developing international standards. ASTM bolt standards and other fasteners almost always appear as ASTM/ASNI.
ASME: The American Society for Testing and Materials. ASME is sometimes confused with ASTM. ASTM issues standards on material properties and testing, while ASME issues standards for materials to be used in construction and infrastructure.
ANSI: American National Standards Institute. While ANSI does not develop standards, they oversee organizations that do.
ISO: International Organization of Standardization, the world’s largest developer of international standards. The ISO standard lists are extensive, from ISO 4762 standard to ISO 7046 specifications.
BSI: The British Standards Institution, along with ANSI, is a member of the ISO..

U.S. standards

American flag to show US fastener standards

Standards include ASTM/ANSI and ASME. You’ll notice in the STANDARD column that sometimes the letter M proceeds a standard. The M stands for metric. This is also spelled out in the THREAD column.

STANDARD	DESCRIPTION	THREAD	MATERIAL

A320L7	L7 Stud Bolt with Nut A320	UNC	Steel
A320L7	Stud Bolt	UNC	Stainless-Steel
ASTMA193	B7 Stud Bolt with Nut A194 2H	UNC	Steel
ASTMA193	Stud Bolt B8M with Nut A194 8M	UNC	Stainless-Steel
B1.20.3	Socket Taper Pressure Pipe Plugs	NPTF 3/4 Taper	Alloy Steel Stainless-Steel Brass
B1.20.3	Socket Taper Pressure Pipe Plugs	NPTF 7/8 Taper	Alloy Steel
B1.5	Allthread ACME	Inch	Grade-5.8 Stainless-Steel-A2
B1.5	Round Flange Track Nut ACME Round Track Nut ACME	Inch	Steel
B16.5	Flange Bolt	UNC	SAE-5(8.8) SAE-8(10.9)
B18.15	Lifting Eye Nut Forged Type A	UNC	Steel
B18.151A	Eye Bolt Forged No Shoulder Type A	UNC	Steel
B18.151B	Eye Bolt Forged No Shoulder Type B	UNC	Steel
B18.152A	Lifting Eye Bolt Forged with Shoulder Collar	UNC	Steel
B18.152B	Lifting Eye Bolt Forged with Shoulder Collar	UNC	Steel
B18.16.3M	Nylon Insert Flange Self Locking Nut	UNC	Steel
B18.2.1	Hexagon Head Bolt Hexagon Head Set Screw External Torx Bolt with Flange	UNC	SAE-5(8.8) SAE-8(10.9)
B18.2.1	External Torx Bolt with Flange	UNC	Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4
B18.2.1	Hexagon Head Bolt Hexagon Head Set Screw	UNF	SAE-5(8.8) SAE-8(10.9)
B18.2.1.1T10	Internal External Toothed Shakeproof Washer	Inch	Spring-Steel
B18.2.1.1T6	Internal Toothed Shakeproof Washer	Inch	Spring-Steel
B18.2.1.1T7	Internal Toothed Heavy Shakeproof Washer	Inch	Spring-Steel
B18.2.1.1T9	Countersunk External Toothed Shakeproof Washer	Inch	Spring-Steel
B18.2.1.1T10	Square Head Bolt	UNC	SAE-5(8.8) SAE-8(10.9) Mild Steel A-A563 Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut Hexagon Lock Nut	UNC	SAE-5(8.8) SAE-8(10.9) Stainless-Steel 18/10-316-A4
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut Hexagon Lock Nut Hexagon Machine Screw Nut Hexagon Allthread Coupling Connector 3D	UNC	Mild Steel A-A563 Stainless-Steel 18/8-304-A2
B18.2.2	Hexagon Heavy Nut Hexagon Allthread Coupling Connector 3D	UNC	Steel-A194-2H Steel C-A563
B18.2.2	Hexagon Allthread Coupling Connector 3D	UNC	Dh-Steel Brass
B18.2.2	Hexagon Structural Heavy Full Nut Slotted and Castle Hexagon Nut Slotted Hexagon Heavy Nut Slotted Hexagon Heavy Nut	UNC	Steel
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut Hexagon Lock Nut	UNF	SAE-5(8.8) SAE-8(10.9) Mild Steel A-A563
B18.2.2	Hexagon Heavy Nut	UNF	Steel-A194-2H Steel C-A563
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut Hexagon Lock Nut	UNF	Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut	Left Hand UNC	SAE-8(10.9)
B18.2.2	Hexagon Full Nut Hexagon Heavy Lock Nut Hexagon Heavy Nut Hexagon Lock Nut	Left Hand UNF	SAE-5(8.8) SAE-8(10.9) Mild Steel A-A563SAE-5(8.8) Mild Steel A-A563
B18.2.2	Square Heavy Nut	UNC	Steel
B18.2.2T1	Square Nut	UNC	Steel
B18.2.5M	12 Point Flange Head Bolt	Metric Coarse	Grade-8.8 Grade-10.9 Grade-12.9 Stainless-Steel-A2 Stainless-Steel-A4
B18.2.6	Hexagon Head Twist Off Tension Control Bolt Round Head Twist Off Tension Control Bolt	UNC	Steel-A325
B18.21.1	Single Coil Square Section Spring Washer Double Coil Rectangular Section Spring Washer External Toothed Heavy Shakeproof Washer	Inch	Spring-Steel
B18.21.1T1	Single Coil Regular Section Spring Washer	Inch	Spring-Steel
B18.21.1T2	Washer Spring, Heavy	Inch	Spring-Steel
B18.21.1T3	Washer Spring, Extra Duty	Inch	Spring-Steel
B18.21.1T4	Washer Spring, Hi Collar	Inch	Spring-Steel
B18.21.1T8	External Toothed Shakeproof Washer	Inch	Spring-Steel
B18.22.1	Narrow Washer Table 2B Regular Washer Table 2B SAE Narrow Washer Table 1A USS Wide Washer Table 1A Wide Washer Table 2B	Inch	Steel Stainless-Steel 18/8-304-A2
B18.22.1	Thin Washer Table 1B	Inch	Steel
B18.22M	American Flat Washer Narrow American Flat Washer Regular American Flat Washer Wide	Metric	Steel Stainless-Steel 18/8-304-A2
B18.3	Socket Cap Screw 1960	UNF	Grade-12.9, Rc38/43
B18.3	Socket Set Screw Cone Point Socket Set Screw Cup Point Socket Set Screw Dog Point Socket Set Screw Flat Point Socket Set Screw Full Dog Point Socket Set Screw Oval Point Socket Set Screw Tip Brass Socket Set Screw Tip Nylon	UNC	Grade-14.9-45H
B18.3	Low Head Socket Cap Screw	UNC	Steel
B18.3	Socket Button Head Screw Socket Countersunk Screw Hexagon Socket Shoulder Screw Splined Socket Button Head Screw Spline Socket Countersunk Screw Torx Socket Button Head Screw Torx Socket Countersunk Screw	UNC UNF	Grade-12.9
B18.3	Socket Cap Screw 1960	UNC	Grade-12.9, Rc38/43
B18.3	Hexagon Socket Shoulder Screw	UNC	Stainless-Steel
B18.3	Low Head Socket Cap Screw	UNC	Stainless-Steel 18/10-316-A4
B18.3	Socket Cap Screw 1960 Socket Button Head Screw Socket Countersunk Screw	UNC	Stainless-Steel 18/8-304-A2 Brass Aluminium Monel Nylon-66 Phospher-Bronze
B18.3	Socket Set Screw Tip Silver Socket Flange Cap Screw	UNC	Steel
B18.3	Hexagon Keys Long Arm Hexagon Keys Short Arm	Inch	Steel Alloy Steel
B18.3	Socket Set Screw Cone Point Socket Set Screw Cup Point Socket Set Screw Dog Point Socket Set Screw Flat Point Socket Set Screw Full Dog Point	UNF	Grade-14.9-45H
B18.3	Socket Cap Screw 1960 Socket Button Head Screw Socket Countersunk Screw	UNF	Stainless-Steel 18/10-316-A4 Brass Aluminium Monel Nylon-66 Phosphor-Bronze
B18.3.3M	Hexagon Socket Shoulder Screw f9	Metric Coarse	Grade-12.9 Stainless-Steel
B18.31M	Engineers Stud Metal End =1.1/2 D	Metric Coarse	Steel
B18.5	Rib Neck Carriage Bolt Cup Square Neck Carriage Bolt	UNC	SAE-5(8.8)
B18.5	Cup Square Neck Carriage Bolt Full Thread	UNC	SAE-8(10.9)
B18.6.2	Square Head Set Screw Cone Pt Square Head Set Screw Cup Point Square Head Set Screw Half Dog Pt Square Head Set Screw Flat Pt Square Head Set Screw Oval Pt	UNC	Case Hardened Steel
B18.6.2	Square Head Set Screw Cup Point	UNC	Alloy Steel Stainless-Steel
B18.6.2	Slotted Grub (Set) Screw Flat Point	UNC	Grade-14.9-45H
B18.6.2	Square Head Set Screw Cup Point	UNF	Case Hardened Steel
B18.6.2	Slotted Grub (Set) Screw Flat Point	UNF	Grade-14.9-45H
B18.6.3	Phillips Pan Head Screw Phillips Raised Countersunk Machine Screw Phillips Raised Trim Countersunk Machine Screw Slotted Cheese Head Machine Screw Phillips Countersunk Head Machine Screw Phillips 100 Deg Countersunk Head Machine Screw Phillips Trim Countersunk Head Machine Screw Slotted 100 Deg Countersunk Head Machine Screw Slotted Countersunk Head Machine Screw Slotted Pan Head Machine Screw	UNC	Grade-4.8
B18.6.3	Square Machine Screw Nut	UNC	Mild Steel A-A563 Stainless-Steel-A2 Brass
B18.6.3	Slotted 100 Deg Countersunk Machine Screw Slotted Raised CountersunkMachine Screw Slotted Raised Countersunk Trim Machine Screw Pozi Raised Countersunk Machine Screw Pozi Raised Countersunk Trim Machine Screw Slotted Mushroom Head Machine Screw Phillips Mushroom Head Machine Screw Pozi Countersunk Head Machine Screw Pozi 100 Deg Countersunk Head Machine Screw Pozi Trim Countersunk Head Machine Screw Slotted Binding Head Machine Screw Pozi Binding Head Machine Screw Phillips Binding Head Machine Screw Pozi Raised Cheese Head Machine Screw Pozi Flange Pan Head Machine Screw Hexagon Head Machine Screw Hexagon Head Machine Screw Large Head Hexagon Head Slotted Machine Screw Hexagon Head Pozi Machine Screw Hexagon Head Phillips Machine Screw Hexagon Large Head Slotted Machine Screw Hexagon Large Head Pozi Machine Screw Hexagon Large Head Phillips Machine Screw Hexagon Washer Head Machine Screw Hexagon Washer Head Slotted Machine Screw Hexagon Washer Head Pozi Machine Screw Hexagon Washer Head Phillips Machine Screw Pozi Mushroom Head Machine Screw Pozi Pan Head Machine Screw Pozi Pan Washer Head Machine Screw Pozi Round Head Machine Screw Pozi Round Washer Head Machine Screw	UNC	Grade-4.8
















B18.6.4	Pozi Pan Head Self Tapping Screw AB	Inch	Case Hardened Steel
B18.6.9A	Wing Nut, American Type A	UNC	Steel Cold Forged Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4 Brass Steel Cold Forged
B18.6.9B1	Wing Nut, Mickey Mouse B1	UNC	Steel Cold Forged Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4 Brass
B18.6.9B2	Wing Nut, Mickey Mouse Tall B2	UNC	Steel Cold Forged Stainless-Steel 18/8-304-A2 Stainless-Steel 18/10-316-A4 Brass
B18.6.9C1	Wing Nut, American Type C1 Die Cast	UNC	Die Cast Zinc-Alloy
B18.6.9C2	Wing Nut, American Type C2 Die Cast	UNC	Die Cast Zinc-Alloy
B18.6.9C3	Wing Nut, American Type C3 Die Cast	UNC	Die Cast Zinc-Alloy
B18.6.9D1	Wing Nut, American Type D1 Stamped	UNC	Steel
B18.6.9D2	Wing Nut, American Type D2 Stamped	UNC	Steel
B18.6.9D3	Wing Nut, American Type D3 Stamped	UNC	Steel
B18.8.1	Split Cotter Pin	Inch	Steel
B18.8.2	Parallel Dowel Pin	Inch	Hardened & Ground Steel
B18.8.2	Spring Tension Pin Slotted	Inch	Spring-Steel Stainless-Steel
B18.8.2	Parallel Dowel Pin	Inch	Stainless-Steel
B18.8.2Coil	Coiled Roll Spring Tension Pin Heavy Duty Coiled Roll Spring Tension Pin Light Duty Coiled Roll Spring Tension Pin Standard	Inch	Spring-Steel Stainless-Steel
B18.9	Countersunk Nib Bolt	UNC	SAE-8(10.9)
B18.9	Domed Countersunk Square Plow Bolt #3	UNC	SAE-5(8.8) SAE-8(10.9)
B18.9	Countersunk Square Plow Bolt	UNC	SAE-5(8.8) SAE-8(10.9) Grade-A(4.6)

How do ISO standards compare?

Within the U.S., the metric system vs standard scenario can now be phrased as the metric system vs. metrics. ANSI is known for the imperial system, but also has metric standards, which differ slightly from ISO metric standards. The U.S. isn’t alone in converting to ISO with little enthusiasm. The Germans, who use their own metric standards (DIN), aren’t too excited either. The cost to convert is enormous when equipment and infrastructure are measured in the home system, so the reluctance is understandable. Still, if everyone wants more success exporting their products on the global stage, one metric standard for worldwide manufacturing is necessary.

The difference between these metric standards lies in the fasteners varying dimensional properties. These fastener specifications are slight. Yet these fasteners are interchangeable.

U.S. standards still require a pitch callout on coarse threads. Here’s how they compare to ISO designations:

ISO THREAD DESIGNATION	U.S. EQUIVALENT
M1.6	M1.6 x 0.35
M2	M2 x 0.4
M2.5	M2.5 x 0.45
M3	M 3x 0.5
M3.5	M3.5 x 0.6
M4	M4 x 0.7
M5	M5 x 0.8
M6	M6 x 1
M8 M8x1	M8 x 1.25 M8 x 1
M10 M10x1.25	M10 x 1.5 M10 x 1.25
M12 M12x1.25	M12 x 1.75 M12 x 1.25
M14 M14x1.5	M14 x 2 M14 x 1.5
M16 M16x1.5	M16 x 2 M16 x 1.5
M18 M18x1.5	M18 x 2.5 M18 x 1.5
M20 M20x1.5	M20 x 2.5 M20 x 1.5
M22 M22x1.5	M22 x 2.5 M22 x 1.5
M24 M24x2	M24 x 3 M24 x 2
M27 M27x2	M27 x 3 M27 x 2
M30 M30x2	M30 x 3.5 M30 x 2
M33 M33x2	M33 x 3.5 M33 x 2

ISO THREAD DESIGNATION

U.S. EQUIVALENT

M1.6

M1.6 x 0.35

M2 x 0.4

M2.5

M2.5 x 0.45

M 3x 0.5

M3.5

M3.5 x 0.6

M4 x 0.7

M5 x 0.8

M6 x 1

M8x1

M8 x 1.25

M8 x 1

M10

M10x1.25

M10 x 1.5

M10 x 1.25

M12

M12x1.25

M12 x 1.75

M12 x 1.25

M14

M14x1.5

M14 x 2

M14 x 1.5

M16

M16x1.5

M16 x 2

M16 x 1.5

M18

M18x1.5

M18 x 2.5

M18 x 1.5

M20

M20x1.5

M20 x 2.5

M20 x 1.5

M22

M22x1.5

M22 x 2.5

M22 x 1.5

M24

M24x2

M24 x 3

M24 x 2

M27

M27x2

M27 x 3

M27 x 2

M30

M30x2

M30 x 3.5

M30 x 2

M33

M33x2

M33 x 3.5

M33 x 2

What are British standards?

Flag of great Britain to show british fasteners

Fasteners made to British standards are still in use, but they’re primarily for the fastener aftermarket. So, for example, BS 4168 fasteners are still out there, but they’re not as readily available as fasteners made to ISO standards. You can also find BS 4183 dimensions so rest assured, you can still get British Standard fasteners.

However, the BSI is in the process of adopting all European standards as British standards – prefixed BS EN or BS ISO – and withdrawing conflicting BS fasteners. The BS fastener standard for inch washers is still popular, but most British fasteners use ISO or DIN standards. DIN is the Deutsches Institut für Normung, the German national organization for standardization.

We’ll show you equivalencies between BS, DIN and ISO, but first, here are British Standards:

STANDARD	DESCRIPTION	THREAD	MATERIAL

BS 21	Socket Taper Pressure Pipe Plugs	BSPT 3/4 Taper	Alloy Steel Stainless-Steel-A4
BS 57	Slotted Mushroom Head Machine Screw Slotted Cheese Head Machine Screw Pozi Countersunk Head Machine Screw Slotted Countersunk Head Machine Screw Slotted Raised Countersunk Machine Screw Pozi Raised Countersunk Machine Screw Slotted Pan Head Machine Screw	BA	Grade-4.8
BS 57	Hexagon Head Set Screw	BA	Grade-R
BS 57	Hexagon Head Set Screw Hexagon Full Nut Hexagon Lock Nut	BA	Grade-A-Steel
BS 57	Hexagon Head Set Screw	BA	Stainless-Steel-A2
BS 57	Hexagon Full Nut Hexagon Lock Nut	BA	Stainless-Steel
BS 57	Hexagon Full Nut	BA	Brass
BS 57	Pozi Mushroom Head Machine Screw Pozi Pan Head Machine Screw Slotted Round Head Machine Screw	BA	Grade-4.8
BS 325	Cup Head Nib Bolt	BSW Whitworth	Grade-4.6
BS 325	Black Square Nut	BSW Whitworth	Class-4
BS 325	Hexagon Black Full Nut	BSW Whitworth	Grade-A-Steel
BS 325	Cup Square Neck Carriage Bolt with Nut Countersunk Square Plow Bolt Countersunk Long Square Plow Bolt For Wood Oval Neck Cup Head Bolts	BSW Whitworth	Grade-4.6
BS 450	Slotted Mushroom Head Machine Screw Slotted Cheese Head Machine Screw Slotted Countersunk Head Machine Screw Slotted Pan Head Machine Screw Slotted Raised CountersunkMachine Screw Slotted Raised Cheese Head Machine Screw	BSF BSW Whitworth	Grade-4.8
BS 450	Pozi Countersunk Head Machine Screw Pozi Raised Cheese Head Machine Screw Pozi Raised Countersunk Machine Screw Pozi Mushroom Head Machine Screw Pozi Pan Head Machine Screw Slotted Round Head Machine Screw	BSF BSW Whitworth	Grade-4.8
BS 450	Slotted Round Head Machine Screw	BSW Whitworth	Brass
BS 856	Wing Nut Mickey Mouse Type DC Wing Nut Type CF	BSF BSW Whitworth BA	Steel Stainless-Steel Brass
BS 1083	Hexagon Head Bolt Hexagon Head Set Screw	BSW Whitworth	Grade-R Stainless-Steel-A2
BS 1083	Hexagon Full Nut Hexagon Lock Nut	BSW Whitworth	Grade-A-Steel Stainless-Steel
BS 1083	Hexagon Lock Nut Thicker 3 Sizes	BSW Whitworth BSF	Grade-A-Steel Stainless-Steel
BS 1083	Slotted and Castle Hexagon Nut	BSW Whitworth BSF	Steel
BS 1083	Hexagon Head Bolt Hexagon Head Set Screw	BSF	Grade-R Stainless-Steel-A2
BS 1083	Hexagon Full Nut Hexagon Lock Nut	BSF	Grade-A-Steel Stainless-Steel
BS 1210	Pozi Countersunk Twin Thread Wood Screw	Metric	Steel
BS 1210	Pozi Countersunk Wood Screw	Inch	Steel
BS 2470	Socket Cap Screw 1936	UNF UNC	Grade-12.9 Stainless-Steel 18/8-304-A2
BS 2470	Hexagon Keys Short Arm	Inch	Alloy Steel
BS 2470	Socket Set Screw Cone Point Socket Set Screw Cup Point Socket Set Screw Dog Point Socket Set Screw Flat Point	BSW Whitworth BSF BA	Grade-14.9-45H
BS 2470	Socket Cap Screw Socket Countersunk Screw Hexagon Socket Shoulder Screw	BSW Whitworth	Grade-X(12.9)
BS 2470	Socket Cap Screw Socket Countersunk Screw	BSW Whitworth BSF	Stainless-Steel 18/8-304-A2
BS 2470	Socket Cap Screw Socket Countersunk Screw	BSF BA	Grade-X(12.9) Stainless-Steel 18/8-304-A2
BS 2693	Engineers Stud Metal End =1.1/2 D	BSF BSW Whitworth	Steel
BS 3032	D Shackle Pins A D Shackle Pins C D Shackle Pins E D Shackle Pins F with Forelock Pin	Inch	Steel
BS 3410	Inch Washer Table 1 BA Inch Washer Table 2 BA Inch Washer Table 3 Heavy Inch Washer Table 3 Light Inch Washer Table 4 Heavy Inch Washer Table 4 Light Inch Washer Table 5 Inch Washer Table 6 Inch Washer Table 7 Inch Washer Table 8 Inch Washer Table 9	Inch	Steel Stainless-Steel Brass










BS 3410	Inch Washer Table 1 BA	Inch	Nylon-66
BS 4162	Flange Bolt	Metric Coarse	Steel
BS 4168	Hexagon Socket Shoulder Screw f9	Metric Coarse	Grade-12.9
BS 4174	Slotted Countersunk Head Self Tapping Screw AB Slotted Countersunk Head Self Tapping Screw B Slotted Raised Countersunk Head Self Tapping Screw AB Slotted Raised Countersunk Head Self Tapping Screw B Hexagon Head Self Tapping Screw AB Hexagon Head Self Tapping Screw B Pozi Countersunk Head Self Tapping Screw AB Pozi Countersunk Head Self Tapping Screw B Pozi Pan Head Self Tapping Screw AB Pozi Pan Head Self Tapping Screw B Slotted Pan Head Self Tapping Screw AB Slotted Pan Head Self Tapping Screw B	Inch	Case Hardened Steel











BS 4174	Round Hammer Drive Screw 'U'	Inch	Steel Stainless-Steel-A2 Brass Copper
BS 4183	Hexagon Machine Screw Nut	Metric Coarse	Steel
BS 4278	Lifting Eye Bolt Forged with Shoulder Collar	UNC	Steel
BS 4320	Form B Flat Washer Form C Flat Washer Form D Flat Washer Form E Flat Washer Form F Flat Washer Form G Flat Washer Table 6 Washer Greater Than M68	Metric	Steel






BS 4320	Form B Flat Washer Form C Flat Washer Form D Flat Washer Form E Flat Washer Form F Flat Washer Form G Flat Washer	Metric	Stainless-Steel





BS 4320	Form B Flat Washer Form C Flat Washer	Metric	Brass Nylon-66
BS 4320	Form B Flat Washer	Metric	Aluminium Polypropylene Titanium
BS 4439	Engineers Stud Metal End =1.1/2 D 4H	Metric Coarse	Grade-8.8 Grade-10.9 Grade-12.9 Grade-4.6 Stainless-Steel
BS 4463	Double Dished (Wave) Crinkle Washer	Metric	Beryllium Copper
BS 4929	Nylon Insert Self Locking P-Type Thick Nut	UNC UNF	Class-8
BS 4929	Nylon Insert Self Locking T Type Thin Nut	UNC UNF	Class-8
BS 4933	Cup Square Neck Carriage Bolt with Nut	Metric Coarse	Steel
BS 7419	Square Square Holding Down Bolts	Metric Coarse	Grade-4.6 Grade-8.8
BS 1802A	Single Coil Square Section Spring Washer	Inch	Spring-Steel Stainless-Steel
BS 1802A	Single Coil Square Section Spring Washer	BA	Spring-Steel
BS 1802B	Rectangular Section Spring Washer	Inch	Spring-Steel Stainless-Steel
BS 1802B	Rectangular Section Spring Washer	BA	Spring-Steel
BS 1802D	Double Coil Rectangular Section Spring Washer	Inch	Spring-Steel
BS 3032T1	D Shackles Small with A Pin	Inch	Steel
BS 3032T2	D Shackles Large with A Pin	Inch	Steel
BS 3032T3	D Shackles Large Bow with A Pin	Inch	Steel
BS 3032T4	D Shackles Small Bow with A Pin	Inch	Steel
BS 3974G	U' Bolt Round Bend To Grip	Metric Coarse	Steel Stainless-Steel
BS 3974NG	U' Bolt Round Bend Not To Grip	Metric Coarse	Steel Stainless-Steel
BS 4278T1	Lifting Eye Bolt Forged with Shoulder Collar	Metric Coarse	Steel
BS 4278T2	Link Eye Bolt Forged with Shoulder Collar	Metric Coarse	Steel
BS 4278T3	Dynamo Eye Bolt Forged with Shoulder Collar	Metric Coarse	Steel
BS 4278T4	Lifting Eye Bolt Forged with Shoulder Collar	BSW Whitworth	Steel
BS 4278T5	Link Eye Bolt Forged with Shoulder Collar	BSW Whitworth UNC	Steel
BS 4278T6	Dynamo Eye Bolt Forged with Shoulder Collar	BSW Whitworth UNC	Steel
BS 7670T3	Weld Screw 3 Nibs Under Head	Metric	Steel
BS 7670T4	Hexagon Weld Nut Standard Collar	Metric Coarse	Steel
BSP	Hexagon Pipe Lock Nut	Metric Coarse	Steel

Comparing DIN, ISO and British Standards

ISO 4762 vs DIN 912 – or are they the same? Is there a British equivalent for DIN 931? What’s DIN 934 or ISO 2340 equivalent to? What’s the din 6914 ISO equivalent? The chart below should help you answer these and other questions.

DIN Standard	ISO Standard	British Standard	Product
DIN 1	ISO 2339		Cone Pins, untempered
DIN 125	ISO 7089		Washers; medium type, primarily for hexagon bolts
DIN 125	ISO 7090		Washers; medium type, primarily for hexagon bolts
DIN 126	ISO 7091		Product grade C washers - designed for use with hexagon head bolts and nut
DIN 127		BS4464B	Spring lock washers with square ends or tang ends
DIN 128			Curved and wave spring lock washers
DIN 137			Spring washers, curved or wave
DIN 1440	ISO 8738		Medium type washers for pins
DIN 1443	ISO 2340		Clevis pins without head
DIN 1444	ISO 2341		Clevis pins with head
DIN 1470	ISO 8739		Grooved Pins, Full Length Parallel-grooved with Pilot
DIN 1471	ISO 8744		Grooved Pins, Full Length Taper-grooved
DIN 1472	ISO 8745		Grooved Pins, Half Length Taper-grooved
DIN 1473	ISO 8740		Grooved Pins, Full Length Parallel-grooved with Chamfer
DIN 1474	ISO 8741		Grooved Pins, Half Length Reverse-grooved
DIN 1475	ISO 8742		Grooved Pins, Third Length Centre-grooved
DIN 1476	ISO 8746		Round Head Grooved Pins
DIN 1477	ISO 8747		Countersunk Head Grooved Pins
DIN 1481	ISO 8752		Spring-Type Straight Pins (Roll Pins) - Heavy Type
DIN 1587			Hexagon domed cap nuts
DIN 1816			Round Nut with Set Pin Holes Inside; ISO Metric Fine Thread
DIN 315			Wing nuts with rounded wings
DIN 316			Wing screws with rounded wings
DIN 404			Slotted capstan screws
DIN 417	ISO 7435		Slotted set screws with long dog point
DIN 427	ISO 2342		Slotted headless screws with chamfered end
DIN 428	ISO 4034		Hexagon nuts, Grade C
DIN 433	ISO 7092		Washers for use with cheese head screws
DIN 433-1	ISO 7092		Product grade A washers - with a hardness up to 250 HV designed for use with cheese head screws
DIN 433-2	ISO 7092		Product grade A washers - with a hardness up to 300 HV designed for use with cheese head screws
DIN 438	ISO 7436		Slotted set screws with cup point
DIN 439	ISO 4035	BS3692	Hexagon thin nuts
DIN 439	ISO 4036	BS3692	Hexagon thin nuts
DIN 439	ISO 8675	BS3692	Hexagon thin nuts
DIN 439-1	ISO 4036		Unchamfered hexagon thin nuts - Product grade B
DIN 439-2	ISO 4035		Chamfered hexagon thin nuts - Product grades A and B
DIN 439-2	ISO 8675		Chamfered hexagon thin nuts - Product grades A and B
DIN 440	ISO 7094		Washers for use in timber constructions
DIN 444			Eyebolts
DIN 462			Machine Tools; Internal Tab Washers for Slotted Round Nuts for Hook Spanner according to DIN 1804
DIN 464			Knurled thumb screws, high type
DIN 466			Knurled nuts, high type
DIN 467			Knurled nuts, low type
DIN 471			Circlips (retaining rings) for shafts; Normal type and heavy type
DIN 479			Square head bolts with short dog point
DIN 5406			Lockwashers and locking plates for use with rolling bearings
DIN 548			Round nuts with set pin holes in side
DIN 551	ISO 4766		Slotted set screws with flat point
DIN 553	ISO 7434		Slotted set screws with cone point
DIN 555	ISO 4034		M5 to M100x6 hexagon nuts - Product grade C
DIN 558	ISO 4018		Hexagon head screws
DIN 580			Collar eyebolts for lifting purposes
DIN 601	ISO 4016		M5 to M52 hexagon head bolts; product grade C
DIN 603			Mushroom head square neck bolts
DIN 609			Hexagon fits bolts with long thread
DIN 6319			Spherical washers and conical seats
DIN 6325	ISO 8734		Parallel Pins, Hardened; Tolerance Zone m6
DIN 6340			Washers for clamping devices
DIN 653			Knurled thumb screws, low type
DIN 6797			Toothed lock washers
DIN 6798			Serrated lock washers
DIN 6799			Lock washers (retaining washers) for shafts
DIN 6900	ISO 10644		Screw and Washer Assemblies
DIN 6901	ISO 10510		Tapping screw and washer assemblies
DIN 6902	ISO 10673		Plain washers for screw and washer assemblies
DIN 6903	ISO 10669		Plain washers for tapping screw and washer assemblies
DIN 6912			Hexagon socket thin head cap screws with pilot recess
DIN 6914	ISO 14399-4		High-strength hexagon head bolts with large widths across flats for structural steel bolting
DIN 6916			Round washers for high-strength structural steel bolting
DIN 6921	ISO 1665		Hexagon flange bolts
DIN 6922	ISO 1665		Hexagon flange bolts with reduced shank
DIN 6923	ISO 1661		Hexagon nuts with flange
DIN 6924	ISO 7040		Prevailing torque type hexagon nuts with non-metallic insert
DIN 6924	ISO 10512		Prevailing torque type hexagon nuts with non-metallic insert
DIN 6925	ISO 7042		Prevailing torque type all-metal hexagon nuts
DIN 6925	ISO 10513		Prevailing torque type all-metal hexagon nuts
DIN 6926	ISO 7043		Prevailing torque type hexagon nuts with flange and with non-metallic insert
DIN 6926	ISO 12125		Prevailing torque type hexagon nuts with flange and with non-metallic insert
DIN 6927	ISO 7044		Prevailing torque type all-metal nuts with flange
DIN 6927	ISO 12126		Prevailing torque type all-metal nuts with flange
DIN 7045			Pan head screws with type H or type Z cross recess - product grade A
DIN 7337	ISO 14589		Break mandrel blind rivets
DIN 7337	ISO 15977 to ISO 15984		Break mandrel blind rivets
DIN 7337	ISO 16582 to ISO 16584		Break mandrel blind rivets
DIN 7343	ISO 8750		Spiral Pins; Normal Type
DIN 7344	ISO 8748		Spiral Pins; Heavy Duty Type
DIN 7346	ISO 13337		Spring-Type Straight Pins; (Roll Pins) Light-weight Type
DIN 7349			Plain Washers for Bolts with Heavy Clamping Sleeves
DIN 7500-1	ISO 7085		Thread rolling screws for metric ISO thread - Part 1: Types, designation, requirements
DIN 7500-2			Thread rolling screws for ISO metric thread; guideline values for hole diameters
DIN 7504			Self-drilling screws with tapping screw thread - Dimensions, requirements and testing
DIN 7513			Hexagon head and slotted head thread cutting screws - Dimensions, requirements and testing
DIN 7516			Cross recessed head thread cutting screws - Dimensions, requirements and testing
DIN 7603			Ring seals and gaskets
DIN 7970	ISO 1478		Threads and thread ends for tapping screws (modified version of ISO 1478)
DIN 7971	ISO 1481	BS4174	Slotted pan head tapping screws
DIN 7972	ISO 1482		Slotted countersunk head tapping screws
DIN 7973	ISO 1483		Slotted raised countersunk head tapping screws
DIN 7977	ISO 8737		Taper Pins with Thread Ends and Constant Point Lengths
DIN 7978	ISO 8736		Taper Pins with Internal Thread
DIN 7979	ISO 8733		Parallel Pins with Internal Thread
DIN 7979	ISO 8735		Parallel Pins with Internal Thread
DIN 7980		BS4464A	Spring lock washers with square ends for cheese head screws
DIN 7981	ISO 7049		Cross recessed pan head tapping screws
DIN 7982	ISO 7050		Cross recessed countersunk head tapping screws
DIN 7983	ISO 7051		Countersunk (Flat) Head Tapping Screws with Cross Recess
DIN 7984			Hexagon socket thin head cap screws
DIN 7985	ISO 7045	BS4183	Cross recessed raised Phillips Pan head screws
DIN 7989-1			Washers for steel structures - Product grade C
DIN 7989-2			Washers for steel structures - Product grade A
DIN 7991	ISO 10642	BS4168	Hexagon socket countersunk head cap screws
DIN 84	ISO 1207	BS4183	Product grade A slotted cheese head screws
DIN 85	ISO 1580	BS4183	Product grade A slotted pan head screws
DIN 9021	ISO 7093		Plain washers with large outside diameter
DIN 908			Hexagon socket screw plugs with parallel screw thread
DIN 910			Hexagon-duty hexagon head screw plugs
DIN 911	ISO 2936		Hexagon Socket Screw Keys
DIN 912	ISO 4762	BS4168	Hexagon socket head cap screws (modified version of ISO 4762)
DIN 912	ISO 21268	BS4168	Hexagon socket head cap screws (modified version of ISO 4762)
DIN 913	ISO 4026		Hexagon socket set screws with flat point (ISO 4026 modified)
DIN 914	ISO 4027		Hexagon socket set screws with cone point (ISO 4029 modified)
DIN 915	ISO 4028		Hexagon socket set screws with full dog point
DIN 916	ISO 4029		Hexagon socket set screws with cup point (ISO 4029 modified)
DIN 918-3			Overview of European Standards for fasteners
DIN 921			Slotted pan head screws with large head
DIN 923			Slotted pan head screws with shoulder
DIN 929			Hexagon weld nuts
DIN 93			Tab washers with long tab
DIN 930			Fine thread pitch partially threaded screws
DIN 931-1	ISO 4014	BS3692	M1,6 to M39 Hexagon Cap Screws Partially Threaded - Product grades A and B
DIN 931-2	ISO 4014	BS3692	M42 to M160x6 Hexagon Cap Screws Partially Threaded - Product grade B
DIN 933	ISO 4017	BS3692	M1,6 to M52 Hexagon Cap Screws Fully Threaded - Product grades 8.8
DIN 934	ISO 4032		Hexagon nuts with metric coarse and fine pitch thread - Product classes A and B
DIN 934	ISO 8673		Hexagon nuts with metric coarse and fine pitch thread - Product classes A and B
DIN 935-1			Hexagon slotted nuts and castle nuts with metric coarse and fine pitch thread - Product grades A and B
DIN 935-2			M42 to M160x6 hexagon head bolts; product grade B
DIN 935-3			Hexagon slotted nuts with metric coarse pitch thread - Product grade C
DIN 936		BS3692	M8 to M52 and M8x1 to M52x3 hexagon thin nuts; product grades A and B
DIN 937			Hexagon thin castle nuts
DIN 938			Studs with a length of engagement equal to about 1 d
DIN 939			Studs with a length of engagement equal to about 1,25 d
DIN 94	ISO 1234		Split pins
DIN 95			Slotted Raised Countersunk (Oval) Head Wood Screws
DIN 96			Slotted Round Head Wood Screws
DIN 960	ISO 8765		M8x1 to M100x4 hexagon head bolts with fine pitch thread - Product grades A and B
DIN 960	ISO 8676		M8x1 to M100x4 hexagon head bolts with fine pitch thread - Product grades A and B
DIN 961	ISO 8676		M8x1 to M52x3 hexagon head bolts with fine pitch thread - Product grades A and B
DIN 962			Designation system for fasteners
DIN 963	ISO 2009	BS3692	Slotted countersunk head screws (with countersunk heads as specified in ISO 2009-1972)
DIN 964	ISO 2010	BS3692	Slotted raised countersunk oval head screws
DIN 965	ISO 7046	BS3692	Cross recessed countersunk flat head screws
DIN 966	ISO 7047		Cross recessed raised countersunk head screws
DIN 970	ISO 4032		Hexagon nuts; Style 1; Metric coarse thread, Product grades A and B; ISO 4032 modified
DIN 971-1	ISO 8673		Style 1 hexagon nuts with metric fine pitch thread; property classes 6 and 8
DIN 971-2	ISO 8674		Style 2 hexagon nuts with metric fine pitch thread; property classes 10 and 12
DIN 972	ISO 4034		M5 to M39 hexagon nuts; style 1; product grade C (modified version of ISO 4034)
DIN 975			Threaded rods
DIN 976-1			Metric thread stud bolts
DIN 976-2			Metric interference-fit thread stud bolts
DIN 977	ISO 21670		Hexagon weld nuts with flange
DIN 979			Hexagon thin slotted nuts and castle nuts with metric coarse and fine pitch thread - Product grades A and B
DIN 980	ISO 7042		All-metal prevailing torque type hexagon nuts
DIN 980	ISO 10513		All-metal prevailing torque type hexagon nuts
DIN 981			Locknuts for use with rolling bearings
DIN 982	ISO 7040		Prevailing torque type hexagon nuts with non-metallic insert
DIN 982	ISO 10512		Prevailing torque type hexagon nuts with non-metallic insert
DIN 983			Retaining rings with lugs for use on shafts (external circlips)
DIN 985	ISO 10511		Prevailing torque type hexagon thin nuts with non-metallic insert
DIN 986			Prevailing torque type hexagon domed cap nuts with non-metallic insert
DIN 988			Shim rings and supporting rings

Note: this is a rough guide and you should always carry out your own trials to ensure you have the right fastener for your application.

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