Spanner Screwdriver Size Chart

How To Check Spanner Size
Spanner Screwdriver Size Chart Inches
Spanner Screwdriver Size Chart Actual
Spanner Screwdriver Size Chart

Kevin C Bacon.(Baconsdozen Imperial tools).Commonly used Whitworth or B.S.F to SAE / A.F (inches across flats) sizes and conversions to metric and decimal inch dimensions.I've prepared these charts from my own experience and research.They are all my own,original work,not plagarised from other web sites or the 'experts' on ebay.If they appear anywhere else,they have been copied from here.The imperial (BSW,BA and AF) tools I have for sale along with extra clearance items are on this single page.

Commonly used Whitworth/BSF thread dia and the mm or imperial (inch) size of the wrench opening to fit nut or head.

The following chart allows you to convert easily between all of the major standards - MM, AF, BSW and BSF - making it a lot easier to find a spanner or socket to fit. Metric bolts, which are measured in MM across flats (edge-to-edge) of the bolt head, are the most common fittings for continental vehicles. Spanner jaws to the exact rated size, using a high-tech grinding machine. Perfect fit is the most important requirement for non-damaging and safe work. Protects bolt heads. The Tamperproof spanner screwdriver is a complete security screwdriver set in one driver. Spanner: 6, 8, 10, 12. Security SAE Hex: 1/8, 9/64, 5/32, 3/16in. A table of common metric spanner and key sizes is shown opposite. Some spanners may be marked AF. This also means Across Flats but it is an Imperial size marking, or more correctly a SAE marking, associated with UNC and UNF screw threads - e.g. A 1/2' AF spanner is 1/2' across and fits a 5/16' diameter UNF nut.

In Japan, the male sizes are often designated as DTC-20, DTC-27, DTC-40 (discontinued) and DTC-45 corresponding to a respective screw head size of 3.2mm, 4.6mm, 6.4mm and 7.7mm; with the size of the screw measured across the widest portion of the mating part of the head. The most common sizes in use for consumer electronics are DCT-20 and DTC-27. Screwdrivers: Main Types&Sizes. Screwdrivers are the basic tools for rotating screws with special slots of different types in their heads (screwing and unscrewing operations). A screwdriver amplifies the hand's turning motion to the small, specially designed working part (tip or blade) that is inserted into the screw's head.

Whitworth (inch).	BSF.(inch).	Actual Metric.(mm)	Actual Inches (decimal)
1/8	3/16	8.64	.340
3/16	1/4	11.3	.445
1/4	5/16	13.34	.525
5/16	3/8	15.24	.6
3/8	7/16	18.03	.710
7/16	1/2	20.83	.82
1/2	9/16	23.37	.92
9/16	5/8	25.65	1.010
5/8*	11/16*	27.94*	1.100
11/16**	3/4	30.48	1.200
3/4*	7/8*	33.02*	1.300
7/8	1	37.59	1.480
1	1 .1/8	42.42	1.670
1 .1/8	1 .1/4	47.24	1.860

Notes.
*You can use the above chart (and the AF/metric chart below) to find equivalents for some missing tools.For example 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.The longer list at the bottom of the page lists all common sizes in numerical order.

** 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.

A few explanations.....British Standard Whitworth (B.S.W) takes its name from the British engineer who invented it as a way of standardising bolt and nut sizes.Whitworth threads are based on an angle of 55 degrees.Commonly found on older (pre 60's) vintage,veteran and classic cars,bikes or early machinery,there are two 'standards' of Whitworth, as during 1924 the sizes of nuts and bolt heads were reduced to save iron and steel.They were all reduced by one size,so that the same spanners and sockets can still be used. The war also demonstrated the need for a standard for nuts.bolts and the tools to work on them as British (mainly BSW and BSF) and US (UNF and UNC) machinery used completely different systems. British Standard fine is in effect the fine version of whitworth with the same thread form but with a greater number of threads per inch.The size marked on a Whitworth or B.S.F (British Standard Fine) spanner refers to the size in inches of the threaded portion on the bolt it fits. Both Whitworth and British Standard Fine were phased out by the 1960s,but some manufacturers carried on using both on applications much later than this. Whitworth thread is coarser than a BSF of the same diameter,but the same spanners are used on both ranges,and are often marked with both Whitworth and BSF sizes .A whitworth spanner or socket is larger than one marked with the same size in BSF for example a 1/4 inch whit is the same physical 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.The easiest way to identify a whitworth or BSF threaded bolt is to measure its diameter and check the thread rate (TPI or threads per inch) with a thread gauge and compare it to the charts below.BSW and BSF socket head screws use AF hex keys not metric.
B.A (British Association) are smaller sized fastenings found on older vehicles electrical fittings,magnetos,dynamos,motors,pumps and instruments etc. B.A thread has an angle of 47 degrees-30 minutes.This was another standard introdued to try and rationalise the sizes of smaller fixings.
A.F means Across Flats and indicates the distance apart the jaws are on an open end wrench (or the parallel sides on a nut or bolt. Usually applied to spanners in imerial (inch based) sizes the smallest increments are normally 1/16 inch (for example 7/16,1/2,9/16 etc) 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) and use a thread angle of 60 degrees.This standard was introduced as the 'new' standard around the 1940s to replace BSW and BSF etc and was supposedly phased out by the 1970's in favour of metric threads and sizes. However like whitworth and BSF,AF it is still encountered in specialised applications and many car and motorbike makers carried on using imperial fittings etc for a long time after they became supposedly obsolete. It is very common to find an older car or bike that left its maker with a mixture of imperial and metric nuts and bolts holding it together. Land Rover and other smaller,specialised car makers used a mixture of imperial fittings into the 1990's.Note also that AF allen or hex keys fit BSW or BSF hex headed socket screws.
Modern metric spanners are marked or sized in the same way as AF but in millimetres,the distance again between parallel faces of an open ended spanner or wrench.They are used on metric threaded fastenings,these have a thread angle of 60 degrees.Metric bolts often have two numbers on the heads,this is a strength rating.Coarse threads (whitworth,unc etc) are more likely to be used on the thread in a casting to give greater strength,most nut and bolt assemblies will use a fine thread,so studs in castings often have a coarse thread end to go in the casting and a fine end to take a nut.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 greater holding power..

AF spanners and sockets (across flats in inches) to Metric (mm).

Bolt dia.	AF spanner size inches	Spanner size MM
1/4 inch	6.35 mm
5.16 inch	7.94 mm
3/8 inch	9.52 mm
1/4 inch	7/16 inch	11.11 mm
5/16 inch	1/2 inch	12.7 mm
3/8 inch	9/16 inch	14.29 mm
7/16 inch	5/8 inch	15.88 mm
11/16 inch	17.46 mm
1/2 inch	3/4 inch	19.05* mm
9/16 inch	7/8 inch	22.22 mm
5/8 inch	15/16 inch	23.81 mm
1.00 inch	25.40 mm
1.1/16 inches	26.93 mm
3/4 inch	1.1/8 inches	28.57 mm

How To Check Spanner Size

Diameter and thread pitches in inches (tpi) for BSW, BSF, UNC and UNF bolt threads
This chart can be used to help identify the thread on a bolt etc. Measure the outside diameter and then count the number of threads per inch. UNC and Whitworth have the same thread rates but the thread form is different,a thread gauge would help to make accurate comparisons.Take into account also the age of the vehicle or machine the fitting is from. Pre 60s Whitworth is more likely,unified threads started replacing BSW and BSF from the early 1950s but the change was spread over many years in some cases.

BA spanner and socket sizes in inches with metric (mm) equivalents BA (British Associated) is an early British standard often found on dynamos,magnetos,distributors,starters and electrical fittings and connections on older 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.although 10BA is the smallest normally encountered.The thread per inch rate is always a fraction (ie) never a whole number varying from 25.4 (0BA) to 72.6 (10BA) for example.

Number BA	BA spanner size across flats in decimal inches.	Metric equivalent
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 the most commonly used BA size)	8.23mm
1BA	.365 inches	9.27mm
0BA	.413 inches	10.49mm.

Application chart for some hub nut,ball joint sockets and box spanners etc (mainly older vehicles).Our hub nut and ball joint sockets and spanners are listed on the relevant pages (ie)AF or SAEand BSW (Whitworth)

Size	Applications	Vehicles	Notes
3/4 inch af	Common wheel nut size.	Very common.11/16 AF commonly used on smaller.	(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 inch AF.	Hub nuts	Land Rover etc (used as substitute for 52mm)	See list at foot of page.**
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 nut **	Some models Land Rover and Range Rover	close equivalent is 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 early taxi cabs*	As above (eight sided).*

All the commonly used spanner and socket sizes,from 10BA up to 60mm with their decimal inch equivalents.This chart shows comparative sizes in increasing B.A, A.F, B.S.W, B.S.F and MM bolt or nuts and can be used for example to find the next size up or down where a spanner (wrench in USA) or socket is too tight or loose on a fixing. It also shows when some spanners and sockets are almost the same physical size although displaying different markings for example 11/32 inch AF and 1/8 inch whitworth are identical. Note that a set of spanners marked in whitworth (often abbreviated just to 'W') or sockets will cover both the whitworth standards (pre and post war) and the BSF ranges, you do not (as some naughty or just ill informed web sites suggest) need to buy two sets!.

0.131 inches = 9 BA

0.172 inches = 7 BA

0.220 inches = 5 BA

0.250 inches = 1/4 inch AF

0.282 inches = 3 BA

0.315 inches = 8mm

0.344 inches = 11/32 AF and 1/8 Whitworth

0.365 inches = 1 BA

0.394 inches = 10mm

0.413 inches = 0 BA (Largest BA size)

0.438 inches = 7/16 inch AF

0.472 inches = 12mm

0.512 inches = 13mm

0.531 inches = 17/32 inch AF (13.49 mm)

0.563 inches = 9/16 inch AF

0.594 inches =19/32 inch AF (15.1 mm)

0.625 inches = 5/8 inch AF

0.669 inches = 17mm

0.709 inches = 18mm (uncommonly used metric spanner size) but often used as a substitute for 3/8 inch whit..

0.748 inches = 19mm

0.781 inches =25/32 inch AF (19.8mm)

0.813 inches = 13/16 AF inch (Common spark plug size).

0.866 inches = 22mm

0.920 inches = 1/2 Whitworth or 9/16 BSF

0.945 inches = 24mm

1.010 inches = 9/16 Whitworth or 5/8 BSF

Spanner Screwdriver Size Chart Inches

1.063 inches = 1 + 1/16 AF inch or 27mm

1.105 inches = 28mm often used as a substitute for 5/8 inch whit (actually .005inch larger).

1.181 inches = 30mm

1.250 inches = 1 + 1/4 inch AF

1.300 inches = 3/4 Whitworth or 7/8 BSF

1.313 inches = 1 + 5/16 inch AF (some ball joints).

1.390 inches = 13/16 Whitworth or 15/16 BSF (not very commonly used).

1.438 inches = 1 + 7/16 inch AF

1.495 inches = 38mm.

1.575 inches = 40mm or 15/16 inch Whitworth

1.625 inches = 1 + 5/8 inch AF

1.688 inches = 1 + 11/16 inch AF

Spanner Screwdriver Size Chart Actual

1.813 inches = 1 + 13/16 inch AF

1.875 inches = 1 + 7/8 inch AF

2.000 inches = 2 inch AF,(A fairly common hub nut size).** see notes in above table.

2.047 inches = 52mm (Some land rover hub nuts) used as substitute for 1 + 1/4 inch whitworth (actually .003 smaller).

2.050 inches = 1 + 1/4 Whitworth or 1 + 3/8 BSF,(another common hub nut size).

2.165 inches = 55mm

A tubular box spanner or six sided socket the next size up might be a solution when the correct size is not available (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. Most impact sockets are six sided. Six sided (sometimes called six point) sockets or ring spanners are also less likely to damage brass or chrome plated 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 .Ring spanners are called box spanners in the US,block spanner is another term for an obstruction spanner and some people refer to C obstruction spanners as crescent wrenches,others use the same term for an adjustable spanner.

Spanner Screwdriver Size Chart

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 theseMy Home page is here.

Some web sites state that Whitworth and UNC fixings are interchangeable.This is not strictly correct,although some will loosely 'fit' 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 encountered 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).

Kevin C Bacon

Baconsdozen Imperial tools

Tel (44) 01472353993 Mobile 07974435627..