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Fasteners: Common Myths, Misconceptions, and Errors

  • The heads are breaking: We hate this phone call more than any other call. In every single case over the past thirty 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.
  • 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 well in wood (except for specially designed parts with reaming wings). Self-tapping screws work well in all 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. It's called "stain less steel" and not never stainless.
  • 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. 400 series stainless is magnetic because of its high carbon content.
  • 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 applications, exhibit much better anti-corrosive properties but that's not a strength issue.
  • 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 invoice and packaging don't match what you asked for.)
  • Sheet Metal Screws / Wood Screws / Drywall Screws / Particle Board 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.
  • Coated vs 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.
  • 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. It works for many, many years without a hitch. One day the rivets stopped working. Turns out the rivets were on one side of the specification and just wouldn't hold the grommet in place.
  • Nylon Insert Lock Nuts: 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? A quick summary is: 300 series and 400 series stainless are RoHS (Restriction of Hazardous Substances) compliant if un-coated and un-plated (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 (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." If you need RoHS compliant material, please ask when you place your order. More and more parts are coming in that are RoHS compliant.

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