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How do I Choose the Correct Self-Drilling and Self-Tapping Screws??

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Self-Drilling Screws

Self-Drilling Screws operate on the same principles as drill bits and other cutting tools. This means that the way in which these screws are used affects their performance as much how they are designed.

Two important factors to consider when selecting a self-drilling screw are, material thickness and types of materials to be joined.

Screw Suitability
Optimal Cutting Parameters by Screw Size

 

 

 

 

 

 

Key Design Features to Consider when Selecting a Suitable Self-Drilling Fastener

  • Drill Flute

    • The length of the drill flute determines the metal thickness that can be drilled. Drill flutes allow the drilled material to exit the hole. If the drill flute becomes completely embedded in the material, the drill chips will clog the flute and cause the cutting action to cease. If this occurs, the heat from the drill chips could cause the drill point to become over-heated and fail.

  • Point Length

    • The drill point is the unthreaded section from the drill point to the first thread. This length must be long enough to completely drill through the material before the threads engage. If the threads engage too early, they can cause the fastener to bind and break.

  • Screw Wings

    • It is necessary to use fasteners with wings when fastening wood, over ½” thick, to metal. The wings will ream a clearance hole and keep the threads from engaging too early. If the threads engage too early, this could cause a separation of the fastened material from the base material (jacking). Once the wings hit the metal material, they will break off allowing the threads to engage.

 

Self-Tapping Screws

Self-tapping screws can tap its own hole as it is being driven into it. They can come with a sharp, piercing tip or a flat, blunt tip. Sharp tipped self-tapping screws are designed for drilling their own hole in soft materials. The flat tipped self-tapping screws will need a pilot hole drilled before being installed. Some self-tapping screws are also self-drilling screws. These screws have a drill-like flute tip that looks like the tip of a center drill, along with the tap-like flute in the leading threads. These screws are very efficient in hard substrate applications.

How the Self-Tapping Ability is Created

  • Hard Substrates – Metal or Hard Plastics

    • Often created by cutting a gap in the continuity of the thread on the screw, this generates a flute and cutting edge similar to those on a tap.

  • Soft Substrates – Wood or Soft Plastics

    • The self-tapping ability can come simply from a tip that tapers to a gimlet point (no flute is needed), the point forms the hole by displacement of the surrounding material rather than any chip forming drilling/cutting/evacuating action.

Fasteners

Fastener Facts and FAQs

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Keeping up with technology is a challenge. Each new gadget has a different feature than its predecessor, but who really knows the difference between the two? If you want to know the difference between the iPhone4 and the iPhone5, you ask someone who works for the company. If you want to know the pros and cons of HDTV versus 3D, you ask somebody in the television industry. If you want to know about construction fasteners, ask us. Below are some questions we are asked more often than others.

What type of screw gun should be used to install self drilling screws?

For optimal performance, the screw gun should meet the following characteristics:

  • 1800 to 2500 RPM variable speed
  • 6 to 8 amp motor
  • adjustable torque sensitive clutch mechanism
  • depth adjusting nosepiece

What is the difference between a self drilling screw and a self tapping screw?

Just because the names sound similar doesn’t mean they are one in the same. A self drilling screw is designed with a drill bit point. That special point helps to drill into metal without requiring holes to be pre-drilled. Primarily used for metal only, self drilling screws are also known as “tek” screws.

A self tapping screw, on the other hand, has a sharp point with threads and is usually designated as either type “A” or “AB”. (The difference between the two types is the thread size and pitch.) A self tapping screw carves its own thread as it’s being installed, similar to a tap. The difference lies in the fact that a self tapping screw, unlike a tap, requires a pre-drilled hole.

What is the difference between 304 and 316 Stainless Steel?

Not only does the shape of the screw, the style of the tip or the pitch of the threads matter, so does the material that makes up the screw. 304 Stainless Steel contains 18% chromium and 8% nickel. Molybdenum (“Moly”) is added in the 316 Stainless Steel so the percentages differ slightly, with 316 containing 16% chromium, 10% nickel and 2% molybdenum. The purpose of adding the moly is to help the fasteners last longer by resisting corrosion to chlorides like salt water or de-icing materials.

What is a flat undercut screw head?

There are circumstances in which you need more thread and less head in a small amount of space. Flat undercut screw heads are supplied to allow more room on the body of the screw for usable thread. The head height of undercut screws is approximately two-thirds the height of standard flat head screws. Drive depths are reduced proportionately.

Is there a security nut available that cannot be removed?

Security fasteners protect property from theft and misuse. Security screws are constructed with specialty heads that prevent any unauthorized person (anyone without the proper, hard-to-obtain tool) from removing them. And, yes, there are security nuts, too. After tightening to the proper torque, the hex section of a break-away nut shears off leaving a conical nut that cannot be removed.