DIY Tools & Techniques David Thiel discusses a variety of screw types and the best material for each.
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A combination screw head works with both a slotted and a Phillips screwdriver — but slotted screwdriver can slip out of this head. A Phillips screw head gives you a lot of torque but the point on the end of the screwdriver can cause it to slip out of the screw head while turning. A square head screw allows the screwdriver to have positive torque with little slipping.
Screws come in a variety of sizes. Small number 0 or 1 brass screws are used for attaching decorative hinges. They are flathead wood screws. Make sure you have the right size screwdriver for these screws. A large screwdriver will strip out the heads.
Sometimes drywall and sheet metal screws are used in wood projects but aren't made specifically for use with that type of material. A sheet metal screw has threads running from the very top of the screw to the bottom of the screw. When putting two pieces of wood together, the threads of the screw may hold the gap between the two pieces open, rather than closing them tightly together. A wood screw does not have threads at the very top, allowing it to pull the boards together tightly. Drywall screws do not have threads at the top. They have thin shanks, with widely separated threads to cut quickly without splintering wood.
Some screws have a gullet at the end that resembles a drill bit. The screw cuts as it goes into the wood, making its own pilot hole as it goes in. The screw does the work of the drill bit and reduces the chance of splitting the wood as you drive it in.
A machine screw without a point is designed to go into a machined piece, like a nut. They are not usually used for wood applications, but they can be used to hold two pieces of wood together, if necessary. T-nuts are threaded inside and can be used for many applications in the shop.
A lag bolt has a hex head and is installed with a ratchet. It’s good for holding a piece of metal to a piece of wood. Drill a pilot hole before screwing a lag bolt into wood because it has a large head.