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Screw Heads and Types

Use this picture guide to find the head or tamper reststant drive type you need for you job.
Once you have found information about what your needs are, you can find

KEEDEX Tamperproof Screws HERE

Screw Sizing Explained

         There are two different numbers when looking for a screw size that need to be understood. Typically, screw sizes are labled something like this- #10-24. To those who are unfamiliar with this number system, this might be confusing. So here is a simple explaination. The first number is the "size" of the screw. They are numbered from # 0-12 increasing as the number increases. After size 12, they are typically sized in fractions of an inch. That second number is as important as the first. It indicates the rate of the thread spiral, or threads per inch (TPI). In order to use a screw, the threads must be spaced the same as the area they are being inserted into, like a bolt for instance. The smaller the number, the further apart the threads run, the more "coarse" the screw thread is considered. The higher that second number, the closer the threads run, the "finer" the screw thread is onsidered. So for instance our above mentioned screw size of #10-24 is a screw that is size 10 and has 24 threads per inch.

Screw Head Types


Also used for general purposes with a lower crown & shallower recess than the round head design.


Installs flush with metal surfaces or
countersinks with softer materials forclean appearance.


Use this head where countersink installation is desired.Rounded head offers deep recess & is visible just above the surface.


The Pan head has a low profile, with a larger diameter head. This high-edged crown allows for increased strength.


The round head is commonly used for general purposes. This head has a high crown with a deep recess & smaller diameter head than truss or pan head designs.


Different than the round head, the truss heads low profile offers added security against vice-grips removal. Large diameter head for increased fastening strength.

Thread types

Sheet Metal
A or AB Thread forming
screw with locating
point. Conforms to
Machine MS
Machine screw
standard thread
straight sheared point
Conforms to

Drive types


The advantages of the slotted head are that: most people have a screwdriver that fits them (sort of); worn drivers are easily reground; a new screw head slot can easily be cut with a hacksaw. For security needs, these are the downfalls of the slotted head. Otherwise the slotted head is the worst screw drive system, and while very common, it is also generally obsolete.

Phillips Head

One of the most common types of drives for screws is the Philips head. This popularity means that everyone has access to a screwdriver that will work for this type of screw. When tightening a Phillips screw with a Phillips screwdriver you will notice that when the torque gets to be too strong, the screwdriver winds itself out of the screw so the screw head would not be ruined or brake off (referred to as camout).


Hex-Pin style Security Screws, as the name implies has an internal pin within the hexagonal socket of the head, requiring a special insert bit or key wrench to insert and remove. This unique feature renders the Hex-Pin style screw tamper proof, reducing the risk of vandals or intruders tampering or undoing the screws. Due to the design of the Hex-Pin style security screw it is suitable for medium torque applications and can be used clockwise or counter clockwise.


Tamper resistant Torx style screws feature a post in the center of the recess. This post will only fit into a tamper resistant Torx style bit. They are also referred to as Torx security drives, Torx security heads, Torx tamper resistant drives, Torx tamper resistant heads, star tamper resistant screw, Torx security drive screw, Torx security screw, Torx security tamper resistant screw


Also known as Snake Eyes, Pig Nose Screws or Twin Hole. They have two small holes drilled into the head. A special twin pin driver bit is required to both tighten and release the screws. Spanner bits come in sizes: #4, #6, #8, #10, #12, and #14

It should be noted that there are also Metric Snake Eyes that have different spacing than spanner, as well as different hole sizes.