Sheet metal screw are fasteners that are design to be used in thin metal, plastic, or wood. Sheet metal screws have a sharp point and coarse threads, and these coarse threads allow the sheet metal screws to cut there own path into the material. Sheet metal screws are different from wood screws because sheet metal screws is hardened to bite into thin materials.
If you select the incorrect sheet metal screw, the sheet metal screw may strip out or pull through the material. You must understand the gauge of an sheet metal screw because the gauge determines the thickness of a sheet metal screw. A higher gauge number mean a thicker sheet metal screw, which is the opposite of how gauge number work for electrical wires.
How to Choose and Use Sheet Metal Screws
You should use a reference chart to select the correct sheet metal screw. A reference chart provide information about the gauge, the threads per inch, and the required pilot hole size. You can use a reference chart to match the gauge of a sheet metal screw to the thickness of your material.
Slimmer gauges have finer threads, and finer threads provide a better grip in ultra-thin materials. Thicker gauges have coarser threads, and coarser threads allow the sheet metal screw to drive more fast into thicker material. The number of threads per inch is important because the number of threads per inch determines how much material the screw hold onto.
If you use a thread that is too fine in heavy material, the sheet metal screw will bind, but if you use a thread that is too coarse, the sheet metal screw will skip. You should always test the pilot hole size on scrap material because the hardness of metal can vary. You must also select the correct length for a sheet metal screw.
The length of a sheet metal screw should be based off the total thickness of the materials you are fastening together. You should use short sheet metal screws for thin materials, and you should use medium length sheet metal screws for everyday fastening tasks. You should use long sheet metal screws only when you are fastening through many layer or thick substrates.
You must ensure that at least three threads of the sheet metal screw pass through the far side of the material. If at least three threads pass through the far side, the sheet metal screw will have pull-out resistance, but if the sheet metal screw is too short, the sheet metal screw will not hold the material secure. The head type of a sheet metal screw determine how the head of the screw sit against the surface.
A hex washer head spreads the load and seals the connection, so a hex washer head is useful for roofing where vibration occurs. A pan head clamps against a surface without digging into the material, so a pan head is useful for enclosures. A countersunk head sits flush with the surface, and a countersunk head is useful for clean surfaces like automotive work.
You must also consider the drive style of the sheet metal screw. A Phillips drive may strip if the bit is not perfectly square, but a square drive resists stripping when you use power tool. A hex socket drive is useful for overhead jobs because a magnetic driver can hold the sheet metal screw in place.
The material and the finish of a sheet metal screw determine how the sheet metal screw resists rust. Zinc plating is a cheap finish that works for indoor use, but zinc plating may fail if moisture reach the sheet metal screw. Stainless steel is a material that is suitable for outdoor use or use near salt.
Black oxide is a finish that is used for discreet applications inside cabinets. Hot-dip galvanized is a finish that is used for structural applications that is exposed to weather. You must avoid using zinc on aluminum because using zinc on aluminum cause galvanic corrosion, and galvanic corrosion will destroy you’re work.
You should follow specific steps to install a sheet metal screw correctly. You should start by using a center punch to prevent the drill bit from wandering, and then you should drill the correct pilot hole. You should hand-start the sheet metal screw to ensure it is straight, and then you should torque the sheet metal screw until it is snug.
You must not over-torque the sheet metal screw because over-torquing can cause thin metal to pull through, but you must not under-torque the sheet metal screw because under-torquing can cause the connection to loosen. You should use tools such as a clutch drill, a magnetic nut driver, and a numbered bit set to make the installation of the sheet metal screw more efficienty. Finally, you should avoid driving the sheet metal screw at an angle because an angled sheet metal screw has half the holding strength then a straight sheet metal screw.
You should of checked the materials first to be sure.
