Gray 9/32 Drive Sockets

[Ayrhead]

Hi Everyone. I came across these yesterday. The number on the side of one of them says TW7GRAY7BA. THE HIGEST NUMBER IS THE SMALLEST SOCKET. THE LOWEST NUMBER TW3GRAY3BA IS THE LARGEST, about 7mm or 9/32
Attached are pictures and they are all 9/32 drive... anyone have information on them?

 

[Private Lugnutz]

I don't have any documented information on them, per se, but I can tell you that 9/32-inch drive was very popular with various technical branches, especially, but not exclusively, aviation, of the US, Canadian, and British armed forces. I have US and British sets.

The "BA" looks like a reference to the British Association standard. It ran from #0 (largest) to #14 (smallest), I believe.

EDIT: I had posted a chart of BA #'s and opening sizes, but it was messed up, so I deleted it. The BA chart in Wiki looks accurate and it presents the opening sizes in metric and decimal inches, linked here.

 

[Farmer J.]

Well, it's what Lugz says. I suppose made by Gray, and here is the information on BA sizing from someone who knows a lot about it.

Spanner Jaw Sizes

Useful guide on spanner to nut/bolt relationships, and the selection and use of spanners and socket sets

www.crawford-space.co.uk

The BA (British Association) sizes were formulated in 1884 and standardised in 1903. Later it was recommended to use them for all sizes below 1/4" instead of BSW/BSF. They are mostly used in electrical and instrumentation applications and continued in common use in the UK more or less until metrication in the 1970s when its use started to decline. Although odd numbered BA sizes have been made and are listed, they are quite rare. In the UK the even number sizes from 0BA down to 8BA are still readily available from electronic component suppliers such as RS Components, but the smaller or odd number sizes are often only available from model-making suppliers and companies offering parts for restoration work.

Spanner Jaw Sizes and corresponding Nut/Bolt Use

Diff (mm)	Jaw Size Millimetres	Jaw Size Inches	Spanner Metric	Spanner AF	Spanner British	Common Nut/Bolt (*=non-preferred)
​	2.97​	0.117​	​	​	10BA​	​
0.23​	3.20​	0.126​	3.2mm​	​	​	M1.6​
0.13​	3.33​	0.131​	​	​	9BA​	​
0.53​	3.86​	0.152​	​	​	8BA​	​
0.11​	3.97​	0.156​	​	5/32 AF​	​	No.0 UNC​
0.03​	4.00​	0.157​	4mm​	​	​	M2​
0.37​	4.37​	0.172​	​	​	7BA​	​
0.39​	4.76​	0.188​	​	3/16 AF​	​	No.2 UNC​
0.14​	4.90​	0.193​	​	​	6BA​	​
0.10​	5.00​	0.197​	5mm​	​	​	M2.5​
0.50​	5.50​	0.217​	5.5mm​	​	​	M3​
0.06​	5.56​	0.219​	​	7/32 AF​	​	​
0.03​	5.59​	0.220​	​	​	5BA​	​
0.37​	5.95​	0.234​	​	15/64 AF​	​	​
0.05​	6.00​	0.236​	6mm​	​	​	M3.5*​
0.30​	6.30​	0.248​	​	​	4BA​	​
0.05​	6.35​	0.250​	​	1/4 AF​	​	No.4 UNC​
0.65​	7.00​	0.276​	7mm​	​	​	M4​
0.14​	7.14​	0.281​	​	9/32 AF​	​	​
0.02​	7.16​	0.282​	​	​	3BA​	​
0.77​	7.94​	0.313​	​	5/16 AF​	​	No.6 UNC & No.10 UNC (bolt)​
0.06​	8.00​	0.315​	8mm​	​	​	M5​
0.23​	8.23​	0.324​	​	​	2BA​	​
0.36	8.59	0.338			1/8 W; 3/16 BSF
0.15​	8.73​	0.344​	​	11/32 AF​	​	No.8 UNC​
0.27​	9.00​	0.354​	9mm​	​	​	​
0.27​	9.27​	0.365​	​	​	1BA​	​
0.25​	9.53​	0.375​	​	3/8 AF​	​	No.10 UNC (nut)​
0.48​	10.00​	0.394​	10mm​	​	​	M6​
0.49​	10.49​	0.413​	​	​	0BA​	​

 

[Ayrhead]

I don't have any documented information on them, per se, but I can tell you that 9/32-inch drive was very popular with various technical branches, especially, but not exclusively, aviation, of the US, Canadian, and British armed forces. I have US and British sets.

The "BA" looks like a reference to the British Association standard. It ran from #0 (largest) to #14 (smallest), I believe.

EDIT: I had posted a chart of BA #'s and opening sizes, but it was messed up, so I deleted it. The BA chart in Wiki looks accurate and it presents the opening sizes in metric and decimal inches, linked here.

Thanks for the prompt response. It probably is the British Association Standard as it is similar where the smallest # is the largest socket size and the highest # is the smallest socket size. Thanks again for the information
Harry

 

[Ayrhead]

Well, it's what Lugz says. I suppose made by Gray, and here is the information on BA sizing from someone who knows a lot about it.

Spanner Jaw Sizes

Useful guide on spanner to nut/bolt relationships, and the selection and use of spanners and socket sets

www.crawford-space.co.uk

The BA (British Association) sizes were formulated in 1884 and standardised in 1903. Later it was recommended to use them for all sizes below 1/4" instead of BSW/BSF. They are mostly used in electrical and instrumentation applications and continued in common use in the UK more or less until metrication in the 1970s when its use started to decline. Although odd numbered BA sizes have been made and are listed, they are quite rare. In the UK the even number sizes from 0BA down to 8BA are still readily available from electronic component suppliers such as RS Components, but the smaller or odd number sizes are often only available from model-making suppliers and companies offering parts for restoration work.

Spanner Jaw Sizes and corresponding Nut/Bolt Use

Diff (mm)	Jaw Size Millimetres	Jaw Size Inches	Spanner Metric	Spanner AF	Spanner British	Common Nut/Bolt (*=non-preferred)
​	2.97​	0.117​	​	​	10BA​	​
0.23​	3.20​	0.126​	3.2mm​	​	​	M1.6​
0.13​	3.33​	0.131​	​	​	9BA​	​
0.53​	3.86​	0.152​	​	​	8BA​	​
0.11​	3.97​	0.156​	​	5/32 AF​	​	No.0 UNC​
0.03​	4.00​	0.157​	4mm​	​	​	M2​
0.37​	4.37​	0.172​	​	​	7BA​	​
0.39​	4.76​	0.188​	​	3/16 AF​	​	No.2 UNC​
0.14​	4.90​	0.193​	​	​	6BA​	​
0.10​	5.00​	0.197​	5mm​	​	​	M2.5​
0.50​	5.50​	0.217​	5.5mm​	​	​	M3​
0.06​	5.56​	0.219​	​	7/32 AF​	​	​
0.03​	5.59​	0.220​	​	​	5BA​	​
0.37​	5.95​	0.234​	​	15/64 AF​	​	​
0.05​	6.00​	0.236​	6mm​	​	​	M3.5*​
0.30​	6.30​	0.248​	​	​	4BA​	​
0.05​	6.35​	0.250​	​	1/4 AF​	​	No.4 UNC​
0.65​	7.00​	0.276​	7mm​	​	​	M4​
0.14​	7.14​	0.281​	​	9/32 AF​	​	​
0.02​	7.16​	0.282​	​	​	3BA​	​
0.77​	7.94​	0.313​	​	5/16 AF​	​	No.6 UNC & No.10 UNC (bolt)​
0.06​	8.00​	0.315​	8mm​	​	​	M5​
0.23​	8.23​	0.324​	​	​	2BA​	​
0.36	8.59	0.338			1/8 W; 3/16 BSF
0.15​	8.73​	0.344​	​	11/32 AF​	​	No.8 UNC​
0.27​	9.00​	0.354​	9mm​	​	​	​
0.27​	9.27​	0.365​	​	​	1BA​	​
0.25​	9.53​	0.375​	​	3/8 AF​	​	No.10 UNC (nut)​
0.48​	10.00​	0.394​	10mm​	​	​	M6​
0.49​	10.49​	0.413​	​	​	0BA​	​

Thanks for the info. Although it didn’t come with a ratchet or extensions, it was in an old Blueish grey metal Gray box. There were a lot of other 1/4 drive sockets in the box as well marked Taiwan... instead of drawing attention to the Gray sockets I just bought the entire box. So, now I have some British Association sockets that I can add to my collection. Thanks again for the chart and the explanation. Harry

 

[Private Lugnutz]

instead of drawing attention to the Gray sockets I just bought the entire box.

Smooth move!

I don't have any BA sockets. I do have a few end wrenches. Small work.