Can anyone tell me what a 1/4"-20 hex bolt means, please.
Many thanks, Roger
Many thanks, Roger
American screw threads
- Thread starter RogerS
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Travis Byrne
Established Member
Hello Roger
The 1/4" is the OD (outside dia.) of the main body of the bolt.
The 20 is the no. of threads per inch. The hex head is a 6 sided head taking 7/16" wrench (Spanner?) If there is a nut, it will probably be the same as the head.
American bolts have two standard threading system. the 1/4-20 is course. the 1/4-28 is the fine threaded one. The threaded portion can be a inch or two or the entire body of the bolt.
Hope that some of this helps with the answer.
There also is the question of grades of Bolts, but thats a differant story.
Travis
The 1/4" is the OD (outside dia.) of the main body of the bolt.
The 20 is the no. of threads per inch. The hex head is a 6 sided head taking 7/16" wrench (Spanner?) If there is a nut, it will probably be the same as the head.
American bolts have two standard threading system. the 1/4-20 is course. the 1/4-28 is the fine threaded one. The threaded portion can be a inch or two or the entire body of the bolt.
Hope that some of this helps with the answer.
There also is the question of grades of Bolts, but thats a differant story.
Travis
The angle of the thread may also vary depending on what it is: BSF, UNF, UNC, ME, BSW,BA, BSC, etc.
The bolt in question will as Travis says have a shank of 1/4" and a thread pitch of 20 teeth per inch whick makes it either Whitworth or UNC. and if it is american then UNC is the likely one.
Jason
The bolt in question will as Travis says have a shank of 1/4" and a thread pitch of 20 teeth per inch whick makes it either Whitworth or UNC. and if it is american then UNC is the likely one.
Jason
Bean
Established Member
Rodger a good buy for problem threads is a zeus book they are a few quid and usually invaluble.
If you are trying to source some fasteners try Model engineering suppliers as they use them up to 1/4" and sometimes above. Failing that a Landrover dealer or a vintage motorcycle dealer/repairermay be worth a try as they used them as well.
Bean
If you are trying to source some fasteners try Model engineering suppliers as they use them up to 1/4" and sometimes above. Failing that a Landrover dealer or a vintage motorcycle dealer/repairermay be worth a try as they used them as well.
Bean
Thanks, guys. That's really useful information.
Out of curiosity where do people buy small quantities of American hex bolts/screws from? It's just the type of useful thing that Whistons' used to deal in but I've not heard of them for years and years.
Roger
Out of curiosity where do people buy small quantities of American hex bolts/screws from? It's just the type of useful thing that Whistons' used to deal in but I've not heard of them for years and years.
Roger
Used these people quite a bit when I was restoring a 1928 Austin Seven.
http://www.namrick.co.uk/
Jason
http://www.namrick.co.uk/
Jason
Excellent site, Jason..many thanks.
I also came across another good site www.chronos.ltd.uk and have just ordered a few bits and pieces from them.
Roger
I also came across another good site www.chronos.ltd.uk and have just ordered a few bits and pieces from them.
Roger
