Baconsdozen imperial and metric tools.

Conversion charts for Whitworth,BSF,af,BA mm. etc.

British Standard Whitworth (BSW) takes its name from the British engineer who invented it.It was an early standard for threads and spanner sizes.The size of a Whitworth or BSF (British Standard Fine) spanner refers to the size of the thread and not the size of the head of the bolt it fits.Whitworth and British Standard Fine were phased out by the 60s,but some manufacturers carried on using it on some applications much later than this.If you are a classic car or motorcycle enthusiast you'll come across Whitworth and BSF sooner or later..(and the hole in the bottom of your new camera is almost certainly tapped 1/4 inch whitworth) Whitworth thread is coarser than BSF,and is often referred to as the fine version of whitworth but the same spanners are used,they are often marked with both Whit and BSF sizes .A whitworth spanner is larger than a BSF so 1/4 inch whit is for example the same size as a 5/16inch BSF.(approx 13.34mm),this occurs throught the sizes so a set of whitworth sockets or spanners will fit an equal number of BSF nuts and bolts.
BA are small sized fastenings found on older vehicles electrical fittings,magnetos,dynamos,motors,pumps and instruments etc.
AF means across flats and indicates the distance apart the jaws are on an open end wrench in inches or fractions of an inch.Usally the smallest increments are 1/16 of an inch but some smaller spanners are marked in 1/32 inch increments.Very rarely af spanners are marked in decimal instead of fractional sizes for example .50 instead of 1/2,.75 instead of 3/4 inch etc.Imperial AF spanners are normally used on nuts and bolts threaded UNC or UNF (Unified Coarse or Unified Fine) Metric spanners are marked or sized in the same way but in millimetres,they are used on metric threaded fastenings.....
Coarse threads (whitworth,unc etc) are more likely to be used on the thread in a casting where strength is important,most nut and bolt assemblies will use a fine thread.Fine threads (BSF,unf etc) have a greater resistance to being shaken loose by vibration.Brass or similar soft metal nuts and bolts are normally coarse threaded for strength.

Whitworth B.S.F to A.F (inches across flats) and Metric conversion tables.
 
Whitworth/BSF head sizes and the metric or imperial Equivalent.
  
Imperial to Metric
 
Whitworth
BSF.
Metric.
Imperial (af).
A.F
MM.
1/8
3/16
8.64
.340

1/4
6.35
3/16
1/4
11.3
.445
5/16
7.94
1/4
5/16
13.34
.525
3/8
9.52
5/16
3/8
15.24
.6
7/16
11.11
3/8
7/16
18.03
.710
1/2
12.7
7/16
1/2
20.83
.82
9/16
14.29
1/2
9/16
23.37
.92
5/8
15.88
9/16
5/8
25.65
1.010
11/16
17.46
5/8
11/16
27.94
1.100
3/4
19.05
11/16
3/4
30.48
1.200
7/8
22.22
3/4
7/8
33.02
1.300
15/16
23.81
7/8
1
37.59
1.480
1.00
25.40
1
1.1/8
42.42
1.670
1.1/16
26.93


You can use the above chart to find equivalents for some missing tools.For example 3/4 inch af and 19mm are very close,or 5/8 inch whit and 28mm,3/4 inch whit and 33mm etc.

Diameter and thread pitches in inches (tpi).BSW,BSF,UNC and UNF bolt threads 


Nominal Bolt diameter inches.

BSW.tpi

BSF.tpi

UNC.tpi

UNF.tpi

1/4

20

26

20

28

5/16

18

22

18

24

3/8

16

20

16

24

7/16

14

18

14

20

1/2

12

16

13

20

9/16

12

16

12

18

5/8

11

14

11

18

3/4

10

12

10

16


This Table gives B.A sizes in Metric/Inch Eqivalent Measurements (ie 6BA is 4.9mm)
BA (British Associated) is an early British standard often found on dynamos,starters and electrical fittings on old British cars and motorcycles

10BA

.117 inches.

2.97mm

9BA

.131 inches

3.33 mm

8BA

.152 inches

3.86mm

7BA

.172 inches

4.37mm

6BA

.193 inches

4.90mm

5BA

.220 inches

5.59mm

4BA

.248 inches

5.59mm

3BA

.282 inches

7.16mm

2BA

.324 inches (Probably most common BA size)

7.54mm

1BA

.365 inches

9.27mm

0BA

.413 inches

10.49mm.


Application Chart for sockets and box spanners (mainly older vehicles).
 
 Size 
Applications
Vehicles 
Notes
 3/4 inch af
 Common wheel nut size.
  Very common.
(19mm)
  15/16 inch af
Wheel nuts
 Pre 1972 Land Rovers
  (24mm)
 1 + 1/16 af 
Wheel nuts 
After 1972 Land Rovers.
(27mm)
 1 +1/4 inch af 
Rear hub nut
 Jowett Javelin
 Virtually every nut and bolt on these vehicles is whitworth or BSF.
 1 + 5/16 inch af 6 point deep socket 
Front hub nuts.
  

Mini,Austin  Allegro,Austin/Morris 1100  and 1300 Austin Maxi.

Front wheel drive hub nuts.Also cranshaft pulley and rear hub on MGB.

 1 + 1/2 inch  af.6 point deep  socket Front suspension ball joints  Mini,Allegro.Austin/Morris 1100 or 1300,Maxi.  Also fits Mini flywheel nuts.
  1 + 5/8 inch af
Rear Hub nut.
 BMC Midget,Austin Healey Sprite etc.

Probably other early BMC rear wheel drive A40 etc.

 1 + 3/4 inch (socket or box)

    Ball joints.

 Some early Leyland vehicles

   Socket must be deep type for ball joint application.
 1 + 13/16 inch af 6 point deep socket 

Front suspension ball Joints

  

Rover group Metro vehicles 
Also ...Modern Triumph motorbikes?.

 Normally impact type.1/2 inch square drive.
 1 + 7/8 inch af
Hub nuts
                 Older BMC (Wolseley 1500 etc).      Available as H/D box or socket.
 2 +13/16 inch af
Rear hub nuts
 Commer TS3
 Rear hub nuts.Front uses 42mm 
 2 +3/4 inch af 
Hub nuts
Bedford 2 Ton
 70mm.
 3 inch af 
Hub nuts
Bedford 3 Ton
 3 + 1/8 inch af 
Hub nuts
Leyland Roadrunner
  

Also some IVECO trucks

7/16 inch whitworth
     Scaffold Spanner
    Scaffold clamps.(with a pointed end the spanner is often called a 'podger spanner').
Still often used but being replaced by metric.
1 +1/8 inch whitworth
Hub Nuts

Morris Minor and other BMC vehicles

           Available as deep socket or box.
1 +1/4 inch whitworth.
Burman gearbox 

(Panther,Vincent motorcyles and many others)
    Nearest equivalent 52mm as below.
 22 mm deep
    Oxygen Sensor

    Modern vehicles

  

Long socket often has 'window' in side.

 27 mm deep  M24 threaded injector sockets.

Most diesel injector sockets cars and light commercials..

Will also fit some sensors.

 28mm deep  HGV diesel injector sockets 
 Scania,Volvo
  Larger diesel injector sockets on many HVG engines.
 52mm six sided socket 
Hub nuts
  

Some models Land Rover and Range Rover
 2 + 1/16 inch af.
 56mm (usually 12 sided)
Hub nut

 Ford Transit 1993 onwards.

Usually 3/4 drive.

 65 mm (usually 12 sided) 
Hub nut

 Ford Transit (before 1993)

 Ford Transit models 130,150 and 190 plus some IVECO.
 50mm Eight sided
Hub nut

 Austin A55,MGA.MGB*

 Note these are octagonal (eight sided).*
 56mm Eight sided
Hub nut

 J2 Van and some taxi cabs*

  As above (eight sided).*
A box spanner or six sided socket the closest size upwards might be a solution in an emergency (ie) a 19mm spanner will probably undo a 3/4 af nut.These may have greater tolerance than 12 sided sockets but there is always a risk of damage to socket and or the fastening.Six sided (sometimes called six point) sockets or ring spanners are less likely to damage brass or chromed fittings.
Whitworth,BSF,metric and imperial spanners are different standards and hence sizes,with few exceptions they are not interchangeable..As well as classic motorcycles from AJS to Vincents,a lot of older cars used whitworth and BSF fastenings .Marine engines like Lister and Gardner use them as well, and were designed to last, so imperial tools might be regarded as obsolete by some but are still essential on such units..
 Damaged bolt heads spoil many a rebuilt classic car or motorcycle,theres no need when the correct spanners are still available from me.Ring spanners are called box spanners in the US,block spanners is another term for obstruction spanners and some people refer to C obstruction spanners as crescent wrenches others use the same term for an adjustable spanner.
If you are still unsure as to what spanner or socket you require to order,measure the nut or bolt with a caliper or accurate ruler across the flats in mm.If you know if the thread is fine or coarse and when the item was made it will help work out what size the original fitting is. Some axle shaft nuts are eight sided,normal bi hex sockets will not fit these.
Click here to go to my Ebid automotive tool auctions,in the US and Canada I sell on Ecrater
Links to to other pages on this site are below.
Spanners and wrenches.
Servicing and repair
Whitworth Tools
Sockets and sets
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