what size UNC/UNF takes a 1/4″ allen key ?

[Frances IoMParticipant @francesiom58905]

needing some easy way of linking to a 1/4″ hex I thought of a cap head screw – Harold Hall states in his Metal workers data book states that a 5/16 UNC/UNF accepts 1/4 key – didn’t seem right to me as head wall would be too thin – my examples require 7/16 key – so what size needs a 1/4 key?

[Frances IoMParticipant @francesiom58905]

[JasonBModerator @jasonb]

5/16" according to this too

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Frances IoM on 21/09/2016 15:17:16:
needing some easy way of linking to a 1/4" hex I thought of a cap head screw – Harold Hall states in his Metal workers data book states that a 5/16 UNC/UNF accepts 1/4 key – didn't seem right to me as head wall would be too thin – my examples require 7/16 key – so what size needs a 1/4 key?

.

This I gotta see

Please post a photo of one of your examples.

MichaelG.

[Gordon WParticipant @gordonw]

Would a 1/4" driver, as used in battery drills be any use ? Loads of styles and cheap.

[Jeff DaymanParticipant @jeffdayman43397]

5/16" UNC SHCS take 1/4" a/f hex key. JD

[Frances IoMParticipant @francesiom58905]

thanks Michael – 7/32 was meant rather than 7/16 but good to know some are observant.

one use was to allow an old motor from a defunct woolies electric screwdriver to drive the carriage screw on my small Perris lathe during demonstrations – also thought I could use one as basis of a simple lantern chuck using the many 1/4 bits that I seem to acquired to lock the screw to be doctored.

My local specialist fastenings shop is currently on holiday otherwise I’d have tried them armed with the 1/4″ hex bar

[Enough!Participant @enough]

1/4" key is standard – see chart. Head dia is .46" so plenty of room.

[Tim StevensParticipant @timstevens64731]

If you need this sort of info in future, you might help us to respond by saying what style of fastener you are considering. A cap screw will take a larger size than a button head or a countersunk head, and a grub screw (US = set screw) will be smaller still.

One details about hex socket drive fasteners is that there are no special keys needed for Whitworth, BSF, or BA. They all rely on the same set of key sizes as those for UNF, UNC etc.

Cheers, Tim

Edited By Tim Stevens on 21/09/2016 18:29:07

[Frances IoMParticipant @francesiom58905]

maybe I was sold non-standard cap heads (Tim I did mention cap head in 1st sentence of 1st post

[john brennan 1Participant @johnbrennan1]

for the record Bandersnatch's post appears to be a facsimile of the cap screw page from ASTM B 18-3 and should be so recognised.

[Michael GilliganParticipant @michaelgilligan61133]

< post deleted … Frances has already said it >

Edited By Michael Gilligan on 21/09/2016 19:18:21

[Enough!Participant @enough]

Posted by john brennan 1 on 21/09/2016 19:09:39:

for the record Bandersnatch's post appears to be a facsimile of the cap screw page from ASTM B 18-3 and should be so recognised.

Dunno – I copied it from Gould Fasteners "Comprehensive Fastener Guide". No reference to the ASTM spec.

But if it keeps the peace ……

[Paul LousickParticipant @paullousick59116]

5/16" UNC Socket head cap screw uses 1/4" key (there are also a few non-standard cap screws)

[Ian S CParticipant @iansc]

In my Pitmans book on aircraft spec bolts AN standard 5/16" UNF uses a 7/32" key, there is no size in that series of bolts, internal wrenching that uses a 1/4" key. I see that the Unbrako bolts use a 1/4" key for 5/16" UNF/UNC bolts.

Ian S C

[Frances IoMParticipant @francesiom58905]

https://xkcd.com/927/ seems to summarise it then?

[Michael GilliganParticipant @michaelgilligan61133]

[Neil WyattModerator @neilwyatt]

There's a ban on posting links to XKCD – they waste too much of my time!

**LINK**

N.

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