Screws – Demystified

Screws are amazingly versatile and powerful fasteners.  The basic concept is used for holding all sorts of things together including wood, plastic and metal.  Different varieties have been developed to maximize efficacy for particular applications.

Driving Methods

Slotted

Slotted screw heads are perhaps the oldest and most common variety; a linear slot in the head accepts a standard, or flat, screwdriver.

Phillips

The phillips head is an improvement to the slotted screw; cross-shaped grooves accept a phillips-head screwdriver.  These heads provide a larger mating surface between the screw and the screwdriver, which minimizes wear and helps prevent slipping.

Hex

These heads do not have any grooves or slots at all; the entire head is hexagonally shaped and they are tightened with a wrench. Since the size of the heads varies, a wrench set or an adjustable wrench is required for driving hex screws.  The tool for Hex screws is commonly known as Allen Key or Hex Key.

Square

Also know as Robertson drive, these heads have a square indentation to minimize slipping; they also require a special driver for tightening and loosening.

One Way

One-way heads are a variation on the slotted screw. They can be tightened with a standard screwdriver, but are tamper-resistant because they require special tools for removal.

Torx

Torx heads have 6-pointed recessions to provide even more surface area for driving. They require the less-common torx screwdrivers and therefore can be considered tamper-resistant.

Head Shape

The various driving methods listed above can be combined with various head shapes below. For example, you can have a Phillips flat head screw or a Phillips button head screw.

Pan Head

Standard screw head profile with average diameter and average height.

Button Head

Similar to a pan head but with a curved top.

Round Head

More pronounced head than a button head.

Flat Head

Flat top with a tapered underside that is intended to be driven into a countersunk hole.

Oval Head

Tapered underside like a flat-head, but with an oval top.

Truss Head

These are large-diameter heads with a low profile.

Fillister Head

Thick profile with a slightly rounded top.

Thread Varieties

In addition to all the head options that are described above, there is a large variety of screw bodies.

Wood Screw

These screws are designed for use in wood. The threads are usually coarse and deep to help them grab the wood.

Machine Screw

These screws have finer threads than wood screws. They are designed to be used in conjunction with a nut or tapped hole.

Sheet Metal Screw

These screws are usually short and have coarse threads designed to grab onto relatively thin sheet metal.

High-Low

These screws have two sets of threads with alternating heights. High-low screws are specifically designed for certain plastics and other low-density materials.

Self-Tapping

Self-tapping or thread-forming screws feature threads designed to tap their own holes. These work well in softer materials such as wood and plastic but are not suitable for harder materials.

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Published in: on February 14, 2011 at 4:54 pm  Comments (3)  

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3 CommentsLeave a comment

  1. I am impressed with this blog. Surprisingly I challenged myself trying to make one similar to this too, but not technically inclined on how to do it.

  2. Button Head Screw…

    […] ding all sorts of things together including wood, plastic and metal.  Different […]…

  3. Great article. I was checking continuously this blog and I’m quite impressed! Extremely useful info particularly the last part. I care for such information a lot. I was seeking this particular info for a very long time. Thank you and best of luck.


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