Self-tapping screws and self-drilling screws are two of the most commonly confused fastener types, but the difference between them matters when you're about to drive a screw into metal or hardwood and don't want a broken bit or a stripped hole. This guide explains what a self-tapping screw is, how it differs from a self-drilling screw, and when to use each one.
What Is a Self-Tapping Screw?
A self-tapping screw creates its own threads as it is driven, eliminating the need for a pre-tapped hole. However, self-tapping screws may still require a pilot hole before installation: the screw can cut threads, but it cannot drill through some hard materials to create its own hole. The pilot hole must be drilled with a standard drill bit first, then the self-tapping screw cuts its own threads as it drives in.
Self-tapping screws are available in several tip and thread styles, including Type A (coarse threads, sharp point), Type AB (coarse threads with spaced starting thread), and Type B (blunt point with fine thread). Self-tapping screws include these Type A, AB, and B point styles for different materials and thread engagement requirements.
What Is a Self-Drilling Screw?
Self-drilling screws, sometimes called Tek screw, feature a drill point tip — shaped exactly like a standard twist drill bit. The drill point tip penetrates the material and creates the hole; the threads that follow immediately cut the mating threads in the same pass. Self-drilling screws eliminate the need for pre-drilled pilot holes, completing drilling and tapping in one operation.
Self-drilling screws are designated by point sizes #1 to #5, where higher numbers indicate a heavier-duty drill point capable of penetrating thicker steel. Point size #1 and #2 handle light-gauge sheet metal and steel framing; point size #3 through #5 penetrate structural steel up to 1/2" thick.
Self-Tapping vs Self-Drilling: The Real Difference
The real difference between self-tapping and self-drilling screws is the ability to create the hole itself.
| Feature | Self-Tapping Screws | Self-Drilling Screws |
|---|---|---|
| Creates own hole | No — typically needs a pre-drilled pilot hole | Yes — drill point tip drills the hole |
| Cuts own threads | Yes | Yes |
| Pre-drilling required | Yes (pilot hole required) | No |
| Also called | Thread-cutting, tapping screws | Tek screws, self-tappers (informally) |
| Material thickness | Any (with correct pilot hole) | Up to 0.500" thick steel |
| Common applications | Wood, plastic, thin metal | Metal roofing, steel framing, HVAC |
All self-drilling screws are technically self-tapping — they both drill and tap. But not all self-tapping screws are self-drilling — self-tapping screws cannot drill their own hole without a pre-drilled pilot hole.
Thread-Forming vs Thread-Cutting Screws
Within the self-tapping screw category, there's a further distinction between thread-forming and thread-cutting:
Thread-forming screws displace material to create threads without cutting — they push the material aside, forming threads by compression. This leaves no waste chips and creates very strong thread engagement because the surrounding material is under compression. Thread-forming screws are used in plastics, aluminum, and some metals where cutting would remove too much material.
Thread-cutting screws cut away material to form threads — they have cutting edges or slots at the tip that remove material as the screw advances. Thread-cutting screws are used in harder materials where thread forming would require excessive torque and risk cracking or stripping.
Do I Need to Drill Before Using Self-Tapping Screws?
Yes — self-tapping screws require a pre-drilled pilot hole that’s the correct size for the screw gauge: too small and you'll strip the drive or break the screw; too large and there won't be enough material for the threads to grip. In very thin sheet metal (under 26 gauge), soft woods, and some plastics, Type A self-tapping screws can be driven without a pilot hole because the material is thin enough for the sharp point to penetrate, but this is the exception rather than the rule. For reliable installation in most materials, pilot holes for self-tapping screws are essential.
How to Tell If a Screw Is Self-Drilling
Self-drilling and self-tapping screws are differentiated by the tip. A self-drilling screw has a blunt tip with two or more angled cutting flutes that look like the end of a twist drill bit. A self-tapping screw has a sharp, pointed tip without drill-bit geometry — just a point with partial threads starting at the tip. If the tip looks like a tiny drill bit, it's self-drilling. If it's just a sharp point, it's self-tapping and needs a pilot hole.
Why Would You Use a Self-Tapping Screw?
Self-tapping screws are ideal for softer materials such as wood, plastic, and thin metal where the thread-cutting action provides strong, reliable grip without the more expensive drill-point tip of a self-drilling screw. Self-tapping screws can be removed and reused depending on the material — the threaded hole remains intact for re-fastening.
What Are the Disadvantages of Self-Tapping Screws?
The main disadvantage is the requirement for pre-drilling. In fast-paced installation work like metal roofing or steel framing, stopping to pre-drill every hole adds significant time — which is exactly why self-drilling screws (Tek screws) were developed and are preferred in metal construction. Self-tapping screws also can't be used in pre-tapped holes; the threads they cut are not standard machine thread and are not interchangeable with machine screws.
Shop Self-Tapping and Self-Drilling Screws at jakesales.com
Find self-tapping screws and self-drilling screws in all types, sizes, and drive configurations at jakesales.com. From lightweight sheet metal applications to heavy-gauge structural steel, jakesales.com carries the right Tek screws and tapping screws for every metal fastening job.