Screw university

Welcome class, to Screw University!  Today we are going to review the different types of screws out there, the types of materials they are made of, head & drive styles, and suggested uses.  Now, we can’t cover every type of screw out there, but these basics should help you get the job done 99% of the time.  Lets get started.

Wood screws, sheet metal screws, lag screws, and self-drilling screws are the most common variety of screws found at your local hardware store. 

Wood screws have a coarse thread and are not fully threaded.  The smooth, unthreaded shaft of the wood screw ensures a tight fit.  Wood screws are intended for wood-to-wood applications.  Coarse thread drywall screws are also commonly used as wood screws.   

Sheet metal screws are fully threaded and not limited to use in metal.  Any time you are screwing through metal (even if you are screwing through metal and into wood) you need to be using a sheet metal screw.  A non-fully threaded screw can get caught where the threads terminate.  A fully threaded shaft will ensure that your screw goes all the way in.

Self-drilling (or tapping) screws are very similar to sheet metal screws.  The main difference is that they have a small cutting bit at the tip.  Self-drilling screws are great for screwing into hard woods or soft metals when you are feeling too lazy to drill a proper pilot hole.

Lag screws are no joke.  The smallest of them start at about 1 inch long and 1/4 of an inch thick and they only get bigger.  Lag screws are hex headed and available fully threaded or not.  If the standard variety won’t cut it, some lag screws are rated to withstand specific amounts of weight.  Around the house, lag screws are most commonly used to screw together heavy lumber or in the mounting of flat screen TVs… but if you ever felt like screwing two cars together, you could do that too.

Your standard screw, of any of the aforementioned varieties, is made of zinc-plated steel.  Common wood screws are brass plated over steel.  There is nothing wrong with steel screws.  They’re cheap, and plentiful, and they work.  Sometimes though, you need to take it up a notch.

Solid brass screws cost more than their plated cousins, but nothing will match the patina on your antique sconce quite like one.  If you live near the beach, brass screws are great for keeping oxidation at bay, just like

Stainless steel.  Stainless steel screws are also rust proof.  If you are mounting something in your kitchen, bathroom, or any other location with a moist presence, I recommend using them.  Another nice thing about stainless steel screws is that they’re stronger than steel screws.  If you need a little added umph, go stainless.

Galvanized screws are, well, galvanized.  I won’t bore you with the details of the galvanization process, but if you’re interested, click here.  Basically, galvanized screws are another way to weatherproof your screws but without the added expense (or good looks) of using pricier materials like brass and stainless steel.   

With the exception of Lag screws (which are only available with a hex head) there are a few options when it comes to the head of your screws.

Flat head screws are used when screwing into a counter sunk hole or when you want your screw to drive flush into your material.

Oval head screws are also intended for use in counter sunk holes, but with an added decorative touch.

Pan head and round head screws ride the surface of the material they are screwed into.  If you need to use a washer with your screw, pan or round head is the way to go.

Hex head screws are driven with a nut driver or ratchet.  When you need a lot of torque, hex headed screws are your best friends.

Your basic flat, oval, or pan headed screws come with a phillips or slotted drive.  The fancier drive types like, torx and hex insert offer more torque, are less likely to strip, and their exotic nature can provide greater security.  The uniqueness of these drive styles also has an aesthetic quality.  Some of the more common, less common drive types are pictured below.   

I hope you enjoyed this crash course on screws.  I am certain I’ve left some things out, but hopefully this little primer will serve you well the next time you need to screw something to something else.

Have a question for Nathaniel? Email it to us and you may just find your answer here next Saturday morning!

Posted by Nathaniel Garber Schoen | Categories: Ask an Expert | Permalink