Difference between Self-Drilling Screws & Self Tapping Screws

Introduction

To the untrained eyes, it often looks like big machines, lumber, pillars and framework are the most important part of a construction project. But people working in such industries understand that without fasteners holding everything together, there would be no construction projects, neither would there be any machines. The construction industry is wholly dependent on the fastener industry for each and every project. Unfortunately, screws, being as small as they are, seldom get the kind of attention they deserve. Understanding various types of screws and their applications is a crucial step in any project. This article will help you in understanding the two most important types of screws – self-tapping and self-drilling screws and the differences between them.

What are Self-Drilling Screws?

Self-drilling screws have a chipped point that allows for the actual drilling to take place with the screw. This essentially means that self-drilling screws can drill their own pilot holes, thus eliminating the need of having it pre-drilled. Self-drilling screws are the most common type of fastener used. These screws feature a tapering kind of shaft that has a continuous thread running all the way from the sharp point till the screw head. The term ‘self-drilling’ is pretty self- explanatory, it signifies that the fastener is capable of drilling itself into any type of material by itself. However, in such types of screws it is mandatory to have a pilot hole to get the screw started. 

What are Self-Tapping Screws?

 Self-tapping screws have sharp threads, which can cut threads into the holes themselves. The sharp edge drills away any material that comes into its way, leaving a space for the screw to get into. Self- tapping screws feature an opposing set of vertical cutting blades on the tip. These blades assist the self-tapping screws to drill their own hole, which avoids the need of getting an actual drill bit. The term ‘self-tapping’, signifies its ability to tap a  hole by itself, thus being able to ‘tap’ into any material. Self-tapping screws are also known as Sheet Metal screws because of their ability to tap into any metal and other hard materials as well. These types of screws are particularly not suitable for tapping into materials such as wood, that requires the screw to make a path into the material for an increased holding capacity. These fasteners are more likely to be used for installing into stones or bricks. Unlike self-drilling screws, the sharp blades of the self-tapping screws helps in tapping a hole of the correct diameter to allow thread insertion into the material, without causing stress on the material it is tapped into.

Self-Drilling Screws V/S Self-Tapping Screws

Here is where the real confusion comes in, all self-drilling screws are self-tapping screws, but all self-tapping screws are not self-drilling.  Basically a self-drilling screw is similar to a sheet metal screw, but doesn’t need a separate pilot hole, as it can drill its own. Both of these fasteners tap their own threads, but to varying degrees. Self-drilling screw’s structure make them ideal for joining thin metal sheets onto wood or metal frames. On the other hand, self-tapping screws are suitable for hard metals that need a pilot hole.

• A self-tapping screw is often known as simply Tapping screws. These are also called Sheet Metal Screws as they are commonly used in metals.
• Whatever name is used, these names are for those screws that primarily form mating threads, which is also known as ‘tapping’ , into a pre-drilled hole, into whichever material it is driven into.
• A self-drilling screw is essentially a self-tapping screw which has an added feature of having a drill point.  Self-drilling screws drill a pilot hole and form mating threads, all in one operation.
• The real confusion is, while describing a screw, people often interchange the term Self-drilling and Self-tapping screws. If a screw can drill its own pilot hole, then it is Self-drilling and if a screw needs pre-drilled holes to get in, then it is a Self-tapping screw.

While we have already discussed that Self-drilling and Self-tapping cannot be used interchangeably, these fasteners come in various configurations and sizes, and are extensively used in the commercial and construction industries.

Applications of Self-Drilling and Self-Tapping Screws

Self-drilling screws are most commonly used in woodworking projects and are also used in drilling soft and thin metals. In case you use a self-tapping screw in wood, the tapped opening will be very large, in such a case the screw threads cannot bear a load more than the minimal pressure. Self-drilling screws  are extensively used in such projects where pilot holes are required. It is important to take care that the screw shaft must be bigger than the pilot hole, so that the fastener can drill in swiftly.

Self-tapping screws are mostly preferred in situations where there is a pre-drilled screw pattern, or there is no deliberate screw pattern. Sometimes it’s hard to tap a hole because the material is extremely thin, or you might not have a rear access to drill a hole. There might be other instances where you might have to disassemble the device later, like in the case of automobiles, etc, so blind reverts don’t work. In such cases, self tapping screws are ideal.  Self- tapping screws are useful for drilling into metals like steel, aluminium, brass, etc. These are mostly suitable for materials that require regular maintenance and work with two different materials that are joined together.

Self tapping screws and self drilling screws, like all other screws in the world, also come in a wide array of specification. Screws are differentiated on the basis of their head type, drive type, thread count, length and diameter.

Common fastener type– Fasteners come in various  types such as Hex, Woods, Sheet metal screws, Machine screws, Lag bolts, Carriage bolts etc.

Drive type-Fasteners also come in various drive types namely- Phillips, Combo, Hex-socket, Star and Square drive.

Length- Fasteners length is measured from where the substrate is assumed to be the end of the fastener. For countersunk fasteners, the length is measured overall. In case of non-countersunk fasteners the length is measured from under the head.

Diameter- The diameter for almost all types of fasteners is measured from the outside.

Thread count- Machine threaded fasteners usually specify a thread density which is measured in Threads Per Inch. For any given diameter, a screw may be available in coarse, fine or super fine thread type.

Head style- Each screw head meets different needs, some of the popular head types are- Bugle head, Composite head, flat head, Button head, Hex head, Oval head etc.

BDN Fastener is a Taiwan based Self-drilling screw manufacturing unit. We offer a wide range of self-drilling and self-tapping screws to choose from. Catering to modern day industrial needs, we offer our customers with high quality ISO-9001 certified products at competitive prices. As screw manufacturers, we offer a wide range of fasteners which are available in regular as well as metric shapes. We also provide appropriate chemical coating to our fasteners for protection against corrosion. With our well- equipped, high-tech equipment we provide quality assured products, which  are manufactured using high grade materials.