Baconsdozen Imperial Tools.

Conversion charts for Whitworth and BSF to mm,af,BA socket and wrench size equivalents etc.
British Standard Whitworth (BSW) takes its name from Whitworth,the British engineer who invented it.Commonly found on classiccars,bikes and early machinery.There are two standards of Whitworth, as during WW2 the sizes of nuts and bolt heads were reduced to save metal.They were all reduced by one size,so that the same spanners and sockets can still be used.
The size marked on a Whitworth or BSF (British Standard Fine) spanner refers to the size of the threaded portion 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.Whitworth thread is coarser than BSF, but the same spanners are used,they are often marked with both Whitworth 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.
B.A (British Association) are smaller sized fastenings found on older vehicles electrical fittings,magnetos,dynamos,motors,pumps and instruments etc.
A.F means Across Flats,and indicates the distance apart the jaws are on an open end wrench in fractions of an inch.Usually the smallest increments are 1/16 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 or 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.Finer threads (BSF,unf etc) have a greater resistance to being shaken loose by vibration.Bolts and nuts in brass or similar soft metal are normally coarse threaded for strength.

Whitworth B.S.F to A.F (inches across flats) and Metric conversion tables.
 
Whitworth/BSF (pre 1940) head sizes and the metric or imperial Equivalent.
  
Imperial to Metric
 
Whitworth
BSF.
Metric.
Inches (decimal)
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

Notes.
*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. Some sockets especially six sided impact might be marked in these examples with both sizes.

** 11/16 inch is not a commonly encountered Whitworth size,13/16 inch and 15/16 inch are even less so and were very seldom specified on engineering drawings 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


BA spanner sizes in inches and metric equivalents 
BA (British Associated) is an early British standard often found on dynamos,starters and electrical fittings on old British cars and motorcycles.The smaller the number the larger the BA nut and bolt.BA sizes right down to 24BA are in fact used.

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

6.30mm

3BA

.282 inches

7.16mm

2BA

.324 inches (Probably most common BA size)

8.23mm

1BA

.365 inches

9.27mm

0BA

.413 inches

10.49mm.


Application chart for hub nut,ball joint sockets and box spanners etc (mainly older vehicles).
 
 Size 
Applications
Vehicles 
Notes
 3/4 inch af
 Common wheel nut size.
  Very common.
(19mm equivalent )
  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).*
     
    Commonly used spanner and socket sizes,from 10BA  to 60mm with decimal inch equivalents.
    This list shows comparisons in BA,AF,BSW,BSF and MM sizes.
     
    0.117 inches =10 BA
    0.131 inches = 9 BA
    0.152 inches = 8 BA
    0.172 inches = 7 BA
    0.193 inches = 6 BA
    0.220 inches = 5 BA
    0.248 inches = 4 BA
    0.250 inches = 1/4 AF
    0.276 inches = 7mm
    0.282 inches = 3 BA
    0.313 inches = 5/16 AF
    0.315 inches = 8mm
    0.324 inches = 2 BA
    0.344 inches = 11/32 AF and 1/8 Whitworth
    0.354 inches = 9mm
    0.365 inches = 1 BA
    0.375 inches = 3/8 AF
    0.394 inches = 10mm
    0.413 inches = 0 BA (Largest BA size)
    0.433 inches - 11mm
    0.438 inches = 7/16 AF
    0.445 inches = 3/16 Whitworth or 1/4 BSF
    0.472 inches = 12mm
    0.500 inches = 1/2 AF
    0.512 inches = 11mm
    0.525 inches = 1/4 inch Whitworth or 5/16 BSF
    0.551 inches = 14mm
    0.563 inches = 9/16 AF
    0.591 inches = 15mm
    0.600 inches = 5/16 Whitworth or 3/8 BSF
    0.625 inches = 5/8 AF
    0.630 inches = 16mm
    0.669 inches = 17mm
    0.686 inches = 11/16 AF
    0.709 inches = 18mm (uncommon metric size).
    0.710 inches = 3/8 Whitworth or 7/16 BSF
    0.748 inches = 19mm
    0.750 inches = 3/4 AF
    0.813 inches = 11/16 AF
    0.820 inches = 7/16 Whitworth or 1/2 BSF
    0.866 inches = 22mm
    0.875 inches = 7/8 AF
    0.920 inches = 1/2 Whitworth or 9/16 BSF
    0.938 inches = 15/16 AF
    0.945 inches = 24mm
    1.000 inch   = 1 inch AF
    1.010 inches = 9/16 Whitworth or 5/8 BSF
    1.024 inches = 26mm
    1.063 inches = 1 + 1/16 AF or 27mm
    1.100 inches = 5/8 whitworth or 11/16 BSF
    1.125 inches = 1 + 1/8 AF
    1.181 inches = 30mm
    1.200 inches = 11/16 Whitworth or 3/4 BSF
    1.250 inches = 1 + 1/4 AF
    1.260 inches = 32mm
    1.300 inches = 3/4 Whitworth or 7/8 BSF
    1.313 inches = 1 + 5/16 AF
    1.390 inches = 13/16 Whitworth or 15/16 BSF (not very commonly used).
    1.417 inches = 36mm
    1.438 inches = 1 + 7/16 AF
    1.480 inches = 7/8 Whitworth or 1 inch BSF
    1.500 inches = 1 + 1/2 AF
    1.575 inches = 40mm or 15/16 Whitworth
    1.614 inches = 41mm
    1.625 inches = 1 + 5/8 AF
    1.670 inches = 1 inch Whitworth or 1 + 1/8 BSF
    1.688 inches = 1 + 11/16 AF
    1.811 inches = 46mm
    1.813 inches = 1 + 13/16 AF
    1.860 inches = 1 + 1/8 Whitworth or 1 + 1/4 BSF
    1.875 inches = 1 + 7/8 AF
    1.969 inches = 50mm
    2.000 inches = 2 inch AF
    2.050 inches = 1 + 1/4 Whitworth or 1 + 3/8 BSF
    2.165 inches = 55mm
    2.362 inches = 60mm
     
     
    A box spanner or six sided socket the next size up might be a solution in an emergency (ie) a 19mm spanner will probably undo a 3/4 inch 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 based on 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 the restoration or repair of 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.
    Links to to other pages on the Baconsdozen imperial tools web site are below.
    AF sockets and spanners
    Servicing and repair
    BSF and Whitworth tools
     Home page.

    Some web sites state that Whitworth and UNC fixings are interchangeable.This is not correct,the thread angle on Unified threads is 60 degrees against the 55 of Whitworth.The thread rates are also different (ie) 1/2 inch whit is 12 tpi and for 1/2 inch UNC is 13.tpi. Other thread forms that may be encounteresd on older machinery include BSP (British Standard Pipe) on fuel,air or oil lines etc and very rarely and on much older machinery BCS (British Standard Cycle)

    Baconsdozen imperial tools
    13 Waveney Road
    Lowestoft
    Suffolk
    NR321BT Tel 01502 584575
    Ordering and contact details click here.