Allen Socket Screws

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niall Y

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Just been trying to order some, cap head, Allen screws. Can anybody enlighten me as to why the longer lengths are only partially threaded, As I was looking for some 50mm long ones fully threaded it was a bit of a pain. However, those of this size, with a button head appear to be fully threaded. Is there a logic to this ?
 
quires why would you want 50mm long fully threaded?
If you need a screw to fasten a panel on say you would only need 12mm or so
Generally you can get up to 25mm fully threaded over that partially…
Ian
Ah.... context is everything. I particularly need the screw to be fully threaded because the threaded socket it engages in is just a few millimetres below the head of the screw. The tip of the screw, in turn, bears against the bottom of a blade about 40mm away and helps to adjust its position.
What puzzles me most it that it only seems to be the cap head Allen screws that are constrained in this way Button head, and hex head are available fully threaded.

I might have cracked it order-wise, in that the supplier didn't state that the screws I ordered were only partially threaded, but to be on the safe side I have also ordered button head ones, that do claim to be fully threaded. :giggle:
 
When I was selling such 'Fasteners' - there was - and I suspect that there probably still is - a distinction between a 'Screw' and a 'Bolt' - the bolt being partially and the screw fully, threaded.
I've never understood a clear distinction between a screw and a bolt, particularly in terms of a machine screw. I pretty much come down to does it connect with a nut? if yes then its a bolt, but I'm not sure that is right?
 
I've never understood a clear distinction between a screw and a bolt, particularly in terms of a machine screw. I pretty much come down to does it connect with a nut? if yes then its a bolt, but I'm not sure that is right?
Correct, but I am afraid Americanisms have crept into the English language and screw which used to be only into wood is now used for bolts as well.
 
A bolt has a head for which you need a spanner. A machine screw is generally slotted for a screwdriver.
Bolts are not generally fully threaded whereas machine screws are. Machine screws are also only available in smaller diameters. You do not usually see them greater than M10.
I'm 62 and have been playing with bits for about 50 years. My description is based upon what I was taught when I was at Secondary school and have then taught throughout my working life.

Colin
 
There seems to be no universally accepted definition between machine screws and bolts that I can see.
There are two useful distinctions below but there are such widespread exceptions to these that you can't rely on either of them

Bolts are only partially threaded, machine screws are fully threaded.
Bolts are made to be used with nuts to hold things together, machine screws are intended to screw into a tapped hole on a machine part
 
Pop into M&E Pearce in Cardigan, they usually have what you need for less than what you can get it for online, ideal if you only need a handful rather than a thousand.
I have used these guys in the past, though they are only really handy if you live in Cardigan. My son does keep telling me that I should support local businesses. But, unless I realise what I need before a regular trip into town, then the cost of petrol has to be added to the transaction which wipes out any cost savings I would get from a small purchase. Which is why I find Ebay and Paypal really convenient for these tiny orders. :giggle:
 
I've always thought bolts were partially threaded and set screws were threaded all the way. Americans call grub screws set screws, which complicates. Coach bolts and coach screws are different although some people seem to use the terms interchangeably.
 
Correct, but I am afraid Americanisms have crept into the English language and screw which used to be only into wood is now used for bolts as well.
Americans call 'countersink head'--- 'flat head', so what do they call a 'counter sink bit', I wonder. A 'flat head' bit??, which to us is 'right daft'.
 
Except the 5mm diameter Allen screws I was being offered were only available partly threaded. So clearly there are exceptions to this rule
 
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