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• The heads are breaking: We hate this phone call more than any other call. In every single case over the past fifty plus years, it's never been the screw. Ever. Not once. Screws have recommended installation torques. Each screw is different, but it's usually around 1000 to 2000 RPM. When you go faster than that, the head will sometimes break. That is not a fastener failure -- that is a user installation failure. "But I've always done it that way," is a common response. For many years asbestos was used in ceilings because they've "always done it that way" -- that doesn't mean it was a good idea, and the many asbestos lawsuits are a testament to that fact.
• It's always worked that way /or/ I've always done it this way: This one causes all sorts of difficulties. Just because it's always worked, doesn't mean it always will. People do things wrong for many years and get away with it. Then you get a piece of metal that's on the high side of a tolerance and a screw that's on the bottom side and it just doesn't work. That doesn't mean something's wrong. And many times when something is wrong, it's an application error. If a part is not designed to work in a particular way, one day it might not work. We had a customer who was using a blind rivet to fasten a grommet to a metal plate. The wall of the grommet was very thin -- outside of specification the rivet was designed for. It worked for many, many years without a hitch. One day the rivets stopped working. Turns out the new batch of rivets were on the high side of the specification and just wouldn't hold the grommet in place -- the difference was 3 microns (.003 of an inch). It happens regularly. Use the right fastener for the application.
• Self-Drilling versus Self-Tapping: These terms are commonly confused. A self-drilling screw has a drill bit style point. They are often called Tek® screws, which is a brand name and not to be used to refer to generic screws. A self-tapping screw has a sharp point normally and is a type "A" or "AB" tapping screw -- though there are other variations, such as "B" point which are blunt. Confusing self-drilling and self-tapping screws is the single most common terminology error we run into daily. Self-Drilling screws are for metal only and do not work in wood (except for specially designed parts with reaming wings). Self-tapping screws work well in most materials, but are likely to need a pilot hole in many applications.
• Stainless Steel Doesn't Rust: That's a commonly believed statement, but it's wrong. Almost all alloys of stainless can eventually rust because they contain traces of carbon. Any metal that has traces of carbon can rust. 302, 304, 18-8, and 316 stainless do rust but it takes a long time. 410 stainless rusts as quickly as steel, but since it's generally surface rust, the integrity of the screw is not usually compromised. Remember, it's called "stain less steel" and not never stains....
• Stainless Steel is not magnetic: In stainless fasteners, 300 series stainless is non-magnetic in its raw condition. Cold working it (making the parts) can sometimes cause traces of magnetism in 300 series, depending on various factors, especially in washers. An increase in magnetism is caused by the heat and friction of cold forming and does not reduce corrosion resistance. A higher portion of nickel can increase stability in stainless, thus decreasing work hardening and any possibilities of magnetism. On the other hand, 400 series stainless is magnetic because of its high carbon content. This article answers the question very well. (For the record 18-8 is a family of stainless steels and includes all alloys from 302 through 305 at the factory's option. Different alloys are used for different types of screws. If you want to know, just ask!)
• 316 stainless is stronger than 304 stainless: That just isn't true. 316 stainless may be slightly stronger in many applications using larger diameter bolts, but 316 is not stronger in any statistically significant way on most standard sized screws. 316 stainless does, in most but not all applications, exhibit much better anti-corrosive properties but that's not a strength issue; see our Technical Library for more on this.
• Trademark Misuse: This happens often. People ask for a Tek® when they really want a self-drilling screw. Or they ask for a Tapcon® when they want a Masonry Concrete Screw. This happens with many brand names (Tampin®, Red Head®, etc) but it can be dangerous. Sometimes these brands have significant differences. It may be hard to believe, but sometimes a fastener costs more for a good reason. When you ask for a particular brand you are implying that you want anchors that meet specific technical specifications and have the proper approvals of the brand name products. More importantly it's illegal to use a trademark to refer to a generic item. It's no different than asking for a Coke® and getting a Pepsi® -- any company that provides you with a brand other than what you ask for is legally required to tell you they are doing so: otherwise it's a simple bait-and-switch. Maybe the substitute you get is as good or better, but maybe it's not: you just don't know. If you want a Tampin® brand machine screw anchor, insist upon it. If you think you've been hoodwinked, asked your vendor for proof or contact the owner of the trademark. (A good sign of trouble is when the quote, invoice, packing slip, and/or packaging don't match what you asked for.)
• Sheet Metal Screws / Wood Screws / Drywall Screws / Particle Board Screws / Deck Screws: Few people know the difference. Here's a short summary. As with all rules, there may be exceptions.
  1. A sheet metal screw is hardened, fully threaded to at least 3 inches, and has a straight shank. They usually have single lead symmetrical threads, though double lead threads are common in some industries. The thread pitch is finer than a wood screw. Most people now use sheet metal screws instead of wood screws -- this is the most common kind of screw used in wood, despite the misleading name.
  2. A wood screw is soft, fully threaded when under one inch in length and threaded approximately ²/₃ of the screw length when over one inch in length, and has a tapered shank. They always have single-lead coarse symmetrical threads.
  3. A particle board screw is hard, fully threaded when under one inch in length and threaded approximately ²/₃ of the screw length when over one inch in length, and has a tapered shank. They have asymmetrical threads and are often waxed or have some form of lubricating agent applied.
  4. A drywall screw is hard, fully threaded when under one inch in length and threaded approximately ²/₃ of the screw length when over one inch in length, and has a almost straight shank. The threads rise well up above the shank of the screw and they all have a bugle or flat head. If doesn't have a bugle or flat head, it's not a drywall screw no matter what anyone tells you. It may be used in drywall but that doesn't make it a drywall screw. Saying something over and over doesn't make it true.
  5. A decking screw is similar to a particle board screw but is generally prepared with superior corrosion resistance.
• Coated versus Uncoated Screws: A lot of people love to say "oh, the grey screws don't work" or some variant thereof filling in whatever color may be appropriate for their complaint. Generally the color of a screw cannot affect its performance in a negative way. Sometimes the color coatings add a bit of lubricity but they don't cause fastener failure.
• Nylon Insert Lock Nuts Making Bolts Break: We often get complaints that the nylon-insert lock nuts don't go all the way on. They're not supposed to. They're supposed to lock after one or two threads clear the locking ring. That's how they work. This is not a defect in the product. You can force them but they'll break or cause the screw to break. If you insist they go all the way, applying dry wax to the bolt will work. Or they make special waxed nylon insert lock nuts which are substantially more money. You may wish to consider a k-lock nut or serrated flange lock nut instead which will go all the way on.
• What screws are RoHS compliant? See our news page for full details, but a quick summary is: 300 series and 400 series stainless are RoHS compliant if uncoated and unplated (our part numbers ending in S, 3, and 4) because in most alloys of stainless steel, chromium is in the metallic state, which is not hazardous. The same goes for other alloys (parts ending in B, R, and A) The chromium in the oxide layer of passivated stainless steel, is dichromium trioxide, which is a trivalent compound. The chromium banned by RoHS is hexavalent chromium. Zinc and HDG parts are generally not RoHS compliant unless the label indicates "RoHS compliant" or "Trivalent" or "Cr3" on it (our part numbers ending in Z, Y, G, Q, H, T, or X.) The actual regulation reads "..if stainless steel bolts and nuts are used as parts, they are not considered to meet the requirement of products specified by Article 5 of the enforcement regulations (ppIII-268). SO, establishments that purchase such parts and handle them as components of manufactured products do not have to make a notification. Regarding the MSDS, if bolts and nuts are used as components by an establishment and they are not processed through fusion or the like (ie welding), they do not meet the requirements of the products, thus MSDS need not be submitted."
• There are other topics of interest discussed on our news page. Look for items marked Informational Bulletin.

What is the difference between a bolt and a screw?

What is the difference between a bolt and a screw? This is a surprisingly common question with a complex answer. There are two three-step critera to go through. The first will tell you if it qualifies as a bolt or screw and the second set tells you which one it is.

1. First and foremost, you cannot tell by the thread length*. The many websites and reference books that make this claim are all wrong and they shouldn't be trusted if they can't get something this basic correct.
2. Secondly, it must be externally threaded and it must have a drive mechanism -- either a head or a drive. So a fully threaded rod (or stud) is neither a bolt nor a screw because it has no head and no drive mechanism. The commonly used term "stud bolt" is erroneous. A stud is not a bolt.
3. Thirdly, it must have continuous threads that circumnavigate the shaft of the part at an angle to the appropriate length* -- the tips of some screws have notches and cuts and special points but that doesn't affect the determination. If it doesn't have external threads, it's neither a bolt nor a screw. Some items that are threaded both inside and outside, such as bushings, are not screws or bolts. If it's got internal threads, it's not a bolt or screw.

Once you've gone through the first three steps, then you know it's a bolt or a screw and not some other fastener.

1. If you need to put it in with a wrench or some other non-drive tool, it's probably, but not always a bolt.
2. If it can't take a nut -- or some other matching thread or tapped mating hole -- then it's a screw. Period. Without exception. (And, before you suggest Lag Bolt, those are properly called Lag Screws though nobody actually calls them that.)
3. If it has a drive (slot, Phillips®, square, Torx®, Allen/Socket/Hex, etc) then it's a usually screw. (Hex/Square Cap Screws are really Hex/Square Machine Bolts with a chamfered washer face, though almost nobody knows the difference, even those in the industry. But a knowledgeable person can tell by looking. Sidewalk Bolts are really screws, but like Lag Bolts, the proper name is not commonly known.) 

Those two three-step criteria are all you really need to make the determination. Are there exceptions? Not many, but some parts can be very confusing. For example, the parts listed below are the only parts that might cause confusion. Sometimes you have to accept what the market calls a product even if it's completely wrong.

• Anchor Bolts (J Bolts, L Bolts, U Bolts, Stud Bolts) are not bolts. These are really just bent and/or cut threaded rods. Remember, for something to be a bolt or screw it must have a drive mechanism. (Incorrect Terminology)
• Hanger Bolts are dual use parts, but they are classified as bolts because it takes a nut and has no drive. (Correct Terminology)
• Toggle Bolts look like screws, but really are anchors and don't qualify as a true bolt or screw. Wedge Bolts® which is a trademark of Powers Fasteners is also an anchor and is not a bolt. (Incorrect Terminology)
• Shoulder Bolts are really screws, but they are not called screws and they are part of the socket family. (Incorrect Terminology)
• Square Head Set Screws are really bolts, but are not called bolts because they are part of the socket family but since they have no drive, they are bolts. (Incorrect Terminology)
• U-Drive screws qualify as screws on a technicality, but they're really friction fasteners -- closer to a rivet or nail -- and are not a true screw as they are installed with a hammer. (Incorrect Terminology)

* Current IFI standards dictate a standard bolt is threaded at minimum twice the diameter plus a 1/4" for all bolts 1" in diameter and smaller and 6" long and shorter. So, a 1" diameter machine bolt that is 2" long is fully threaded and 5" one is not. It's still a bolt. A screw for wood is threaded 2/3" of the length with a 1" minimum. A screw for metal is fully threaded up to 3" minimum. Bolts designated A325, A490, and such follow ASTM specifications for thread length and not IFI. Metric standards follow the DIN book for thread length.