What You Need To Know About Screws
Believe it or not, “Screwing around” is actually a construction industry term. It refers to those times when carpenters are assembling something with screws instead of nails. And if you believe that we have some wet land in Florida we would like to sell you.
Kidding aside, the ancient Greeks actually invented screws. Not for assembling things but for lift water and crush grape. Pretty big screws. The Romans were actually the first folks to use screws for fastening. Their use soon disappeared from the Roman landscape. Probably because each screw was made by hand filing the grooves. Created that way today, each screw would cost about $50. Anyway, once the Romans decided that screws were too expensive their use ended until about the time Queen Elizabeth took the throne. Still expensive, screws were used by the wealthy while everyone else used nails and pegs.
We are all aware that modern technology has insured that nuts, bolts and screws will be competitively priced and available to everyone. What you may not be aware of is that threaded connectors of all kinds have far more holding power than nails. It is no wonder that screws are becoming more and more common in everyday construction – especially remodels.
Roof leaks, squeaky floors and drywall divots can all be almost completely eliminated by using screws instead of nails. When nails that hold down roof sheathing pop up through the paper roofing underlayment a leak can easily occur. Screws go in and stay in. When the floor joist dry out and the nails that hold the subfloor loosen you can bet the floor will start to squeak. And nothing holds drywall tighter longer than a drywall screw. Get our point – and threads?
No, screws aren’t used for structural connections in home construction. But, they are great for holding sheeting of all kinds. In the last few years screw guns have become automated. Plastic bands containing dozens of screws are fed through a driver tip that can firmly place a screw all the way into a 2×4 every second or so. Although a nail gun is faster, automated screw guns like the Rocker can drive screws completely home faster than the speediest carpenter can nail. Cabinets and furniture strength is improved every time a threaded connector is added.
There are many types of screw heads but there are four basic ones: flat, oval, round and pan head. The flat screw is normally used when the head has to be countersunk. Oval head screws are used in decorative applications. Part of the head is countersunk and part remains above the surface. Decorative washers are used with oval head screws to enhance their decorative value and to hold a larger surface. Round head screws are used where appearance is not important but where gripping power is. The deepest slot in a screw is found in the round head. Last but not least the pan head screw is mostly used for sheetmetal work. The head is flatter and broader than the others. Since the head can’t normally be countersunk into metal its flat profile makes for a cleaner finish. Because sheetmetal connections can be very thin the threads of the pan head screw go all the way to the head. Now you know why wood screws can’t be used to hold sheetmetal connections. Right, too much distance between the head and the first thread. Aren’t you smart!
Screws have slotted heads and some have an X-shaped slot called a Phillips head. Another special type of head is the square slot. Of the three we have found that the square head can be tightened tighter than the others. However, for ease of use and availability we always try to purchase the Phillips head type. Where the slotted tip will slip out when using an electric screwdriver, the Phillips head tip usually does a perfect job.
By now you have probably noticed that wood screws have threads about two-thirds of the way up the shaft and the last third is smooth and larger in diameter than the threaded portion. You might say that predrilling for a screw requires three drill bits: one for the tip, one for the shank and one for the head. True, but a special drill bit is available that will drill all three holes in one felled swoop – its called a countersink bit. Check this one out. It definitely makes screwing around easier.
Sliding the screw threads over bee’s wax before installation will reduce the job of driving it all the way home. Since most screws are made of brass or steel it is important not to use soap as a lubricant. The caustic compounds in the soap can eventually cause the screw to deteriorate.
Bolts are even stronger than screws. The slotted round-head stove bolt is great for small jobs. Larger jobs that require a hefty connection are assembled with machine bolts and Industrial Washers. Here two wrenches can be used more forcefully than the screwdriver-wrench combination used to tighten a stove bolt. The combination round-square head of the carriage bolt is great for decorative applications and in locations where security is required. For example, an exposed gate hinge can’t be removed if it is installed with the carriage head exposed. The carriage head has no slots and the square section of the head is designed to interlock into a square hold in the hardware into which it is being installed. The lag bolt is nothing more than a giant screw, but the holding power is unbelievable. Lag bolts can be used in wood or combined with lead lag shields to provide secure connections in concrete, stone and other masonry.
Dowels and nails are great, but there is nothing like a project assembled with threaded connectors. Enjoy your next challenge, and, good luck!