Screw and Fasteners

http://homepages.tesco.net/~A10bsa/bswgo.htm may prove interesting as an aside.

2) Preload is the tension in the fastener with the equipment at rest. In the case of a fastener used to secure something onto a piece of equipment under pressure, the tension in the bolt does not change between the rest state and the test pressure.

machinery's handbook

1. A screw is a fastener. Specifically they are threaded fasteners and come with a variety of head / drive types. The Machinery's Handbook is a good resource. If you're looking for screws for purchase, try to search for screws. There are many other types of fasteners including bolts, rivets, anchors, etc.

2. Preload is the tension from initially tightening a nut on a bolt.

3. Fasteners come in a variety of materials (steel, stainless steel, aluminum, titanium, etc.) and the intended application should be considered when choosing the materials. A variety of finishes or treatments are also available.

4. ASME B18.24 PIN system is a self-contained code that covers 788 unique B18 fastener types from 72 ASME B18 source documents. Many other standards for fasteners exist, AIA, NAS, SAE, etc.

5. Not sure what you're looking for here...

6. Fastener choice is laregely dependent on application. If you have additional information more specific to your application, you might get a better answer.

5: Might be thread pitch, measured in threads per inch for imperial; or possibly torque settings, how many foot pounds the fastner should be tightened to. Of course there's also length, diameter, strength ratings, thread angle. Hmmm, seem to be lots of figures attached to fastners!

How many in a packet?!

Designations differ between imperial & metric screws, imperial generally being major diameter and threads per inch, metric being major diameter and thread pitch. Check out your local supplier & treat their stock range as a set of standard sizes.

Why don't you just go to the library and take out a book on fasteners?

1) About the only thing I can tell you is that a screw can self tap and need nothing to keep it in place where as a fastener usually needs some type of locking piece.

other than that Machinery Handbook is a great resource.

Per the Machinery's Handbook and other technical sources, a screw is a threaded item that does not require a nut for its final use. A bolt is an assembly consisting of a screw that is secured with an external fastener such as a nut.

So, certain fasteners can become bolts, but they all start life as screws!

Ing. Robert Forbus

For metric fastener (bolt outer diameter measurement give a metric round figure) The M (metric) -Thread is the most common thread. On the other hand. The imperial fastener will be designated by UNC (unify coarse) or UNF (unify fine) thread.

The imperial and metric thread both have two(or more) type of pitch. one is standard (coarse) pitch and the other(not so common) is fine pitch. coarse pitch would be fine for most application, but for some percision or special application, fine pitch would be specify. All thread is shape trapezoid (forgot how to spell).

there are also some non-common thread available, like TPI thread with square shape, BSP, NPT or other pipe thread that you can specify to a machine shop and customize your thread.

How about a bolt (or is it a screw!) that's screwed into a piece of machinery via a tapped hole. No external nut but definitely an identity crisis!

Pedantic to the last!

screw is one type of fastner it self. since it is of most common type and being used in almost every walk of life it has become a category of its own. the fastners covers so many variety of means for holding together two or more pieces together like in an assembly of any equipment.

fastners includes nuts of different types and of materials, dowel pins, inserts for using with softer material and harder material bolts/ studs etc.

Machinery handbook on world of screws is an ideal reference book to look at for screws of different types for variety of applications.