Capscrew?

A bolt is used with a nut to hold two pieces together. The bolt passes completely through holes in both pieces, and screwing the nut on the bolt draws them together.

A screw holds one piece onto another by passing through a hole on the held piece and into a threaded hole in the other piece.

I took this info from my old drafting textbook, Engineering Drawing and Graphic Technology; French, Vierck, and Foster; McGraw, New York, ©1993; pgs. 517 & 518.

If I can find an illustration for threaded fasteners online that is similar to the one in the book, I'll try to post it here.

Thanks but the question is "What is a capscrew"?

A capscrew is one which uses an Allen Wrench to fit into a socket on the screw.

As opposed to a hex-head screw which uses a socket to fit the head of the screw.

Sort-of ...............

You can have socket head cap screws and also hex head cap screws. Regardless, "cap screws" are just that, they have a flat cap to them (and can have a nut placed on them, or no nut in a blind hole)

http://www.mustangfasteners.com/images/capscrew-zinc-ss.gif

"Screws" are countersunk and do not accept a nut:

http://www.artestuff.com/images/screw-standard.jpg

Your wrong! a socket screw or bolt is not a cap screw. Its a socket head!

A cap screw or bolt is a hex head, ala Your second statement.

when buying screws or bolts the preferred statement is to mention the design of the head . as pan head cap screw, philips head cap screws , fillister head cap screws ect.

oilcan13

Seems as if there are many types of cap screws. The one pictured above came from this site, but there are many other types as you have already seen. I don't know how a customs officer could distinguish between the cap screw above and a bolt. I know I could not.

Come to think of it, why should cap screws be exempt? It would be a lot simpler if bolts, screws and cap screws were all treated similarly at customs.

From what I have seen in illustrations, the major visible difference between a bolt and a screw is the length of the thread on the shaft. I believe screws have more thread, but a check of specs in Machinery's Handbook or some other reference would tell for certain.

The picture I have placed here is a very good example of a socket head cap screw. I worked in a machine chop for many years and this is what a socket head cap screw referred to.

Unbrako was always the screw manufacturer we used and if you check out their site at the link below, there is a downloadable e-catalogue which shows pretty clearly what a cap screw is.

http://www.unbrako.com/index.htm

nice Grade 8

The picture is not that of a cap screw. Many vendors don't know a thing.

A cap screw has an inside socket for an Allen wrench or other shape drivers.

Don't rely on screw and hardware vendors, they are like snake oil salesman.

The above is a hex head bolt, as was stated before on this thread.

I cannot find your definition of a cap screw anywhere. Is it something you came up with on your own or do you have some reference for your claim? So far as I can see, a cap screw might have an inside socket for an Allen wrench, but it does not necessarily have to have it.

Dictionary definitions say that a cap screw is a bolt which holds two parts together without the use of a nut. Frankly, I don't think the distinction is clear. If there is a nut, it is a bolt, otherwise it is a cap screw...does that make sense?

Even more interesting...why does our government arbitrarily make a distinction between bolts and cap screws insofar as duty or taxes are concerned? Why do we have to abide such silliness? You know perfectly well that foreign suppliers will simply label the product "cap screws" instead of bolts in order to avoid duty and tax. Why should we participate in such bloody foolishness? Maybe it is time to blow the whistle on our government!

There is nothing arbitrary about it. After an indepth investigation it is found that china and Taiwan are "dumping" certain fasteners in the North American market in violation of WTO regulations. This is not a question of regular duty. The guilty companies, and anyone else interested, was/is invited to participate in the investigation before a decision is reached. The whole idea behind world trade, free trade and/or fair trade is that it should take place on a level playing field. We have many methods of making sure that is the case.

It is arbitrary to make a distinction between a bolt and a cap screw when there is no clear distinction. A cap screw is a bolt.

Wikipedia says:

Hex cap screws – "ASME standard B18.2.1 -1981 specifies Hex Cap Screws that range in size from ¼ inch to 3 inches in diameter. These fasteners are very similar to hex bolts. They differ mostly in that they are manufactured to tighter tolerances than the corresponding bolts. The Machinery's Handbook refers parenthetically to these fasteners as "Finished Hex Bolts"^[8]. Reasonably, these fasteners might be referred to as bolts but based on the US government document, Distinguishing Bolts from Screws, the US government might classify them as screws because of the tighter tolerance^[9]."

YourDictionary.com says:

"a kind of bolt used in a tapped hole, usually without a nut, as for fastening cylinder covers, etc."

Answers.com says:

"A long-threaded bolt, usually with a square head, used in fastening machine parts."

The Free online Dictionary says:

"A long-threaded bolt, usually with a square head, used in fastening machine parts."

The American Heritage Dictionary says:

"A long-threaded bolt, usually with a square head, used in fastening machine parts."

Sheldon Brown's Bicycle Glossary says:

Cap Screw"A threaded fastener designed to screw into metal, with a head that is expected to stick up above the surface. Cap screws are commonly used on bicycles to secure bottle cages, luggage racks and other accessories. Cap screws are also used in many other locations on bicycles, but the nomenclature "cap screw" is rarely if ever used by practical mechanics. Most people call these "bolts" in practice, though sticklers may contend that is not proper usage.

See the Wikipedia article on Screws for more details on this."

Please read Bluestone's post #14. The indusrty has a definition and it is contained in ASME B18.2.1. If Wikipedia disagrees with that (which it doesn't, it even quotes the standard but does not reprint it in full) who really cares. Wikipedia's authotity comes from where?

The same goes for dictionaries which define words, not international industry standards. Geeze if I could use a dictionary for this who needs CR4. Before I post a question to CR4 I will have read all those explanations, and from the ones you quoted you should understand why I come here.

In France, a boulon (bolt) consists of a vis (screw) and a ecrou (nut).

Perhaps our terminology has become a little lax and we use screw and bolt too indiscriminately. Interestingly Wiki states "A universally accepted distinction between a screw and a bolt (in the context of threaded fasteners) does not exist."

See Wiki http://en.wikipedia.org/wiki/Screw#Differentiation_between_bolt_and_screw for a good explanation which seems to sum up the discussion so far.

Screws are threaded within 2.5 pitches of thread from face of head head, bolts have threads 2 X Diameter + 6mm up to 125mm long. Cap screws round (domed) head, slotted head (for screwdriver), hexagon or spline socket heads or countersunk hex socket heads.

The best way to tell them apart is:

SCREW: When you use a screwdriver to drive them (Can be Panhead, CSK etc.)

BOLT: When you use a spanner (open Jaw or Ring or socket) as the driving tool

CAPSCREW: (Also known as Allen bolt) when Allen key wrench is used for driving.

As an afterthought!!

A Capscrew can be more appropriately defined as a device having machined threads on the outer with a 'Countersunk' (CSK or tapered head) CAP at one end used for holding together or tightening, a minimum of two surfaces using a hexagonal Allen key or wrench.

The CSK part goes into the taper drilled top surface such that after tightening, there is no projection on the surface and the screw is flush in the hole. When the round head CAP stays above the surface and is also driven by Allen key, it is referred to as a Allen CAPbolt.

AHA ...... may I ask where this definition comes from because this is the first one that speaks of the underside of the screw head. This is what we were told is going to differentiate between a capscrew and normal screw but that seemed to contradict what I had found previously.

Believe it or not the previous definition I had said, "cap" was from the word capture, and a cap screw was one that went into a previously threaded part, instead of a nut.

That definition can be found in ANSI Std B18.2.1. All threaded fasteners are covered by national and international standards that are generated by various technical committees and working groups. Those standards are available individually but all are contained in collections (including the one I consider the best) titled, "Fastener Standards", published by the Industrial Fasteners Institute (http://www.indfast.org) for both inch and metric threaded fasteners. Both will also include specifications for identification of bolts and screws along with other useful information (weights, recommended torques, thread standards, etc.). The IFI website also includes several other publications, documents, links and references. It would be worth your time to take a look at it.