Technical Information

Dimensional Specifications

DIN 931 & DIN 933

The drawing below shows unthreaded fasteners. The thread length of Metric bolts manufactured to DIN 931 and 933, with diameter d and thread length t, is:

t = 2d + 6mm up to 125mm;

t = 2d + 12mm from 125mm until 200mm;2d + 25mm at 200mm and over.

(Click on the image to enlarge)

din 931

BS 1083

The drawing below shows unthreaded fasteners. The thread length of BSW or BSF bolts manufactured to BS1083, with diameter d and thread length t, is t = 2d.

(Click on the image to enlarge)

bs1083

BS 1768

The drawing below shows unthreaded fasteners. The thread length of UNC or UNF bolts manufactured to BS1768, with diameter d and thread length t, is:

t = 2d + 1/4" up to a length of 6", where the formula becomes t = 2d + 1/2".

(Click on the image to enlarge)

bs1768

How to measure

Measuring bolt diameter

Bolts can be accurately measured using a vernier.

For metric bolts, the prefix 'M' is added to denote Metric. For example, a 4mm diameter bolt is commonly known as an 'M4' bolt. Imperial bolts are measured in inches.

Measuring bolt length

The length of a Hexagon bolt is determined by measuring from underneath the head to the end of the bolt. If the bolt has a countersunk head, the full length of the bolt including head is measured.

Measuring threads

Metric bolts are identified by measuring the distance between the threads - a 1mm pitch bolt has 1mm between the threads.

The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

See the thread charts on this page for more information.

A thread gauge can be used to identify bolts and nuts, although they are not in common usage. The Thread Detective is a quick and easy solution to the problem of identifying bolt and nut threadforms, allowing quick and precise identification of Metric, UNC & UNF bolts and nuts.

thread detective - thread identifierThread Detective - Thread Identifier

Thread Charts

Metric

Metric bolts are identified by measuring the distance between the threads in millimetres - a 1mm pitch bolt has 1mm between the threads.

DiameterCoarseFineExtra FineSuper Fine
M10.250.2
M1.60.350.2
M20.40.25
M2.50.450.35
M30.50.35
M40.70.5
M50.80.5
M61.00.75
M71.00.75
M81.251.00.75
M101.51.251.00.75
M121.751.51.251.0
M142.01.51.251.0
M162.01.51.0
M182.52.01.51.0
M202.52.01.51.0
M222.52.01.51.0
M243.02.01.51.0

Imperial

The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

DiameterUNCUNFBSWBSF
No.44048
No.63240
No.10 / 3/1624322432
1/420282026
5/1618241822
3/816221620
7/1614201418
1/213201216
9/1612181216
5/811181114
3/410161012

BA

BA is an imperial threadform. The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

BA numberTPIDia (inch)
647.90.11
438.50.142
334.80.161
231.40.185
025.40.236

Mechanical Properties

Metric

Property4.68.8
<= M16
8.8
> M16
10.912.9
Min Tensile N/mm240080083010401220
Min Lower Yield Stress N/mm2240
Min Proof Stress N/mm26406609401100
Hardness Min HRC22233239
Hardness Max HRC32343944

BSW & BSF

PropertyRTV
Min Tensile tonf/in2455565
Min Yield Stress tonf/in2344152
Hardness Brinell201/285248/335293/370

UNC & UNF

PropertySTV
Min Tensile tonf/in2505565
Proof Stress tonf/in2384149.5
Hardness Brinell223/310248/335293/370

Torque figures

Metric coarse

 M6M8M10M12M14M16M20M22M24M30M36M42
4.6 kgf m0.461.122.233.896.219.6518.825.632.664.7113181
8.8 kgf m1.233.05.9510.3516.525.750.268.386.6172300478
10.9 kgf m1.734.228.3514.623.236.270.796122242423678

Metric fine

 M6M8M10M12M14M16M20M22M24M30M36
4.6 kgf m0.501.202.354.246.7210.320.928.135.471.5120
8.8 kgf m1.343.26.2511.317.927.355.775.094.5189316
10.9 kgf m1.904.528.815.925.238.578.5105132268448

UNC

 1/45/163/87/161/29/165/83/47/811.1/81.1/41.3/81.1/2
S lbf ft9203556851231703004857301035146019202540
T lbf ft10213658881271753115007501065150019652610
V lbf ft122545731111602123936329501345190024803300
 

UNF

 1/45/163/87/161/29/165/83/47/811.1/81.1/41.3/81.1/2
S lbf ft11224062961371923355357951075150020402690
T lbf ft12234164991411953456508201100154021002760
V lbf ft1428508112518023843569510001390195026503500

BSW

 1/45/163/87/161/29/165/83/47/811.1/81.1/41.3/81.1/2
R lbf ft8173047701051452554106208751235 -2150
V lbf ft1225457210716021039062894513301890 -3280

BSF

 1/45/163/87/161/29/165/83/47/811.1/81.1/41.3/81.1/2
R lbf ft918325177112155268432650930130017302270
V lbf ft142749781181732244106609951420199026303480