How to Choose the Right Screw Types for the Job

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How to Choose the Right Screw Types for the Job

Screws come in many sizes, lengths, and materials for different kinds of work. Wood screws have coarser threads than metal screws, for example, and screws used outdoors should be treated for rust resistance. Each kind of screw is best for certain kinds of assembly. Simply recognising different screw heads will help you find the right screw.

 

Screw Shapes and Materials

Screws are made from steel, stainless steel, or aluminium. Speciality machine screws may be made from plastic or nylon. These materials are also used for the wall plugs used with screws. Screws, such as decking screws, that are exposed to outdoor weather, should have at least a black finish or be galvanised to prevent rusting. Stainless steel screws are the most durable outdoors but also most expensive. Different screw heads suit different uses.

 

Screw Head

Description

Uses

Flathead or Countersunk

Flat head with tapered base, allowing head to be countersunk

Furniture making

Round Head

Rounded sides, rounded top, flat base

Fastening materials that do not allow countersinking; often used with a washer

Pan Head

Rounded sides, flat on top

Assembling sheet metal

Oval Head

Rounded sides, rounded top, tapered base

Assembling sheet metal

 

Screw Slot Types

Another variation in screws is the slot type. The kind of slot determines what screwdriver works with the screw, which further focuses the screw's best uses.

 

Slot Type

Description

Uses

Straight

Single slot in head

Connecting simple joints not under significant tension

Phillips

Cross-shaped slot in head

Assembly in appliances, electronics, woodwork, drywall

Pocket-Hole, Torx, Hex

Holes shaped like square, five-sided star, or hexagon

Making secure connections by screwdrivers, including pneumatic tools, with high torque

Hex Head Self-Tapping or Tek

Hex head with washer

Use with screw gun on wood or metal for roofing and wall sheathing

 

Wood Screws and Plasterboard Screws

Wood screws have sharp points, wide shafts, and require a guide hole. They generally have flat heads so they rest flush with the surface. Plasterboard screws are narrower with coarser threads. These do not usually require a guide hole. Molly bolts are speciality screws for supporting heavy items on plasterboard walls. As the screw is turned, a metal flange wrapped around the shaft opens to create a 360-degree support fan behind the wall.

 

Metal Screws

Metal screws have narrow threads. Sheet metal screws have flat heads that lie flush against the project surface. Self-tapping screws have a sharp tip so guide holes are unnecessary. Such designations as M6 or M5 match screws to metric thread sizes in machinery. Metal screws may have Phillips slots or any slot used with pneumatic tools.

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