I Was Going To Throw These Away

I had my hand over the trash can, then thought one of you nut and bolt nuts might want them. Should date to 1951-52. All 1/4" fine thread. Free.

10 AUTO R 1/4" x 1/2"
2 AUTO R 1/4" x 5/8"
2 BEES 1/4" x 3/4"

Keep them, Mike. You may just need those as you make progress on your 120 - they will be British Standard thread and some captive nuts etc. will require them.

I can most certainly use these fasteners. PM Sent

Harold Lang


You got 'em!

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Much appreciated Mike

I’ll never use them. The hex head is odd sized. Very slightly larger than a 7/16" socket, but too small for 1/2". Like it should be 15/32"? I’m very happy to use new screws and chase any captive threads UNF.

Yes, they’re Whitworth, so you’d need a separate set of wrenches and sockets to use them … in any case, there’s no more deserving recipient than Harold, who’s helped me out many times over the past several years.

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1/4 BSF hex heads on 1/4-28 ANF threaded bolts.
Roger Payne would no doubt have an explanation as to why the British fastener industry would do that.

BSF - British Standard Fine
BSW - British Standard Whitworth

Both are Whitworth sizes. BSW uses the next size up spanner for the same size head as BSF. It’s an evolutionary thing…
Some manufacturers, particularly pre-war, used BSW on suspension components but BSF on body and mechanical parts. BSW stopped being used in automotive applications sometime just post-war, I think.

I guess I misunderstood.
So they are 1/4-26 BSF rather than 1/4-28 ANF?
ANF was used on XK120 chassis and engine parts, but BSF was used on XK120 body and gearbox parts.

I did not count the threads. These were in a bag with a bunch of oval washers. Most of them were attached to one of the washers with a matching nut (also going to Harold). They are all 1/4" shank size.

They remind me of the bolts used to secure the valence panels in between the engine bay and front wheel wells. I remember when I got my first '120 how frustrating it was to try and remove them with a 7/16" wrench. It never quite fit and the heads or nuts would shear off due to decades of rust and dirt. My smoke wrench helped. I quickly learned they were Whitworth and as my motorcycle uses them, dusted off my wrenches for that.

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I have a set of Whitworth sockets, but they are 1/2" drive, not the thing I’m looking for when faced with a 1/4" fastener.

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Could be them. I recently hung the rear wings. First thing I did was to chase all of the cage nuts with a 1/4-28 tap. (EDIT: This size is wrong. They were 5/16, now 5/16 UNF)

For the rear wing securement I remember them on mine as being at least 5/16" shank. Did you change the size on yours? If you mean the small valence panels in the rear wings then yes, those are 1/4" shank.

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The UK transitioned from British thread standards to SAE from the late '40s to about the mid '50s. The branding ‘BEES’ and ‘AUTO’ were the high strength range used on Mk IV and V and are only BSF threads with Whitworth heads. Mk IV was only Whitworth standard but the Mk V was W and SAE and had tools in the toolkit to cover both standards of hexagon.

One oddity about this transition was MG - for the engines, they had metric fine threads with Whitworth hexagons - a legacy from 1914/18.

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Mine as well.

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Oh, I think you are correct on that. I chased all of them 5/16 UNF. Bad memory.

Mike, what date is your car? The captive nuts for my June 1955 140’s rear wings are 5/16" BSF. I believe later that year they switched to UNF. I would assume that all 120s and early 140s had BSF threads here (mine were all pointed-tip BEES fasteners).

April, 1952. They are 5/16". The car came to me completely disassembled, so I have no idea what screws came from where. I had to drill out a couple snapped off screws, but I chased every one of them with a 5/16 UNF tap, so they are UNF now.