Difference Between Bolts And Machine Screws

"Michael" wrote in message news:bkxii.16982$ snipped-for-privacy@text.news.blueyonder.co.uk...

Chris

I've always called them set screws (fully threaded length) rather than machine screws. Conversely, I've always thought of machine screws as rather small diameter set screws with a c/sunk head.

Peter

They're only for *small* machines

Big machines need big machine screws. I don't think they need to be countersunk, they can have round, pan, whatever, heads.

Tim

Wikipedia told me that machine screws have thread on the whole length, but it didn't specify what is classed as a bolt - so I figured it may be something to do with the thread length.

Cheers,

Michael

That's what I thought. I think we're basically right, but another common definition seems to be that a screw is intended to screw into a part, whereas a bolt is designed to be usee with a nut. Like most things, it can get much more complicated.

This page says that some very short bolts can have threads all the way to the head.

There's even a 21 page document to help US customs decide whether to use the duty rate for bolts or screws, which are apparently different!

Dave

(Yes, I was bored)

I suppose we should approve of customs officers and other subterranean life-forms being given pointless 21-page documents to try to understand.

From my earlier career, I must say I found customs duties even more stupid and pointlessly complex than VAT, and that's saying something.

David