Self-drilling (TEK) screws: will it drill your steel?
A self-drilling (TEK) screw has a tiny drill-bit point on its tip, so it bores its own hole — no pilot needed. But only up to that drill point's rated steel thickness. Pick the drill point number and how thick your steel is to see whether it'll get through.
Which drill point?
The point number — on the box, or by the tip. A longer drill tip = a higher number.
…and how thick is the steel?
Total thickness of all the steel the screw drives through.
Will it self-drill?
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No pilot — until the point runs out of steel
A self-drilling screw has a tiny drill-bit point on its tip — it looks like a miniature twist drill, flutes and all. That point bores the hole and the threads follow, in one drive. So in metal a TEK screw needs no pilot hole. That’s the whole appeal, and it’s the opposite of a self-tapping screw, which cuts threads but not the hole.
The catch is the limit. A drill point only bores so much steel — the deeper the point, the thicker the steel, and that’s the point number. Ask it to go past its rating and the point burns out before it penetrates: the screw stops advancing, spins in the hole, and the friction work-hardens the steel so it bites even less. The head shears or the point rounds off. So the real question isn’t “what pilot” — it’s will this point get through my steel, which is what the tool answers.
Point ratings are the total steel thickness — every layer you’re fastening counts together — and they vary a little by manufacturer, so treat the tool as a starting point and check the box. Aluminium and other soft metals drill far easier than steel, so a point rated for a given steel thickness handles more soft metal; the steel figures are the conservative case.
Driving a TEK screw cleanly
- Let the point drill first. Hold the screw square and steady until the tip bores through, then let the threads pull it home — don’t lean so hard the threads engage early.
- Use a moderate speed. Too fast overheats and dulls the point; too slow in thick steel just polishes it.
- Drive with a nut driver or hex bit that matches the head, ideally in an impact or a clutch drill, so you can back off the instant it seats.
- Match the point to the steel. If it stalls and spins, the point’s too small for the stock — step up a point number or pre-drill.
- Wear eye protection; the point throws hot steel swarf.
- For structural or load-bearing work, follow the screw manufacturer’s published drilling capacity.
Common questions
Do self-drilling screws need a pilot hole?
No. A self-drilling (TEK) screw has a small drill-point tip that bores its own hole and cuts its own threads in one pass, so no pilot is needed — up to the drill point's rated steel thickness. A #3 point self-drills up to about 3/16" (0.21") of steel; a #5 point up to 1/2". Past that rating the point burns out before it gets through, so a thicker plate has to be pre-drilled. (The screw that DOES need a pilot in metal is a self-TAPPING screw — a different fastener.)
What's the difference between self-drilling and self-tapping screws?
The point. A self-DRILLING (TEK) screw has a visible little drill-bit tip — it looks like a tiny twist drill — that bores its own hole, so it needs no pilot in metal. A self-TAPPING screw has a sharp or blunt point with no flutes; it cuts its own threads but not its own hole, so in metal it needs a pre-drilled pilot. They're easy to mix up because both get called "self-tappers," but the drill point is the tell. This page is self-drilling screws; for the self-tapping pilot size, use the self-tapping screw tool.
How thick a steel will a TEK screw go through?
It depends on the drill point number, not the screw gauge. A #2 point self-drills up to about 0.11" (roughly 12 gauge); a #3 up to about 0.21" (3/16"); a #4 up to about 3/8"; a #5 up to about 1/2", which is the practical limit for the category. Those are total thickness — all layers being fastened count together. The exact rating varies by manufacturer, so check the box, and for structural work follow the maker's published data.
Why won't my self-drilling screw drill through?
Almost always the steel is thicker than the drill point is rated for. Once the point can't get through, it overheats and dulls, the screw spins in place, and the friction work-hardens the steel — so it drills even less. Step up to a higher point number (a #4 or #5 for thick plate) or pre-drill the hole with a cobalt bit. Driving too fast, leaning too hard, or a worn point cause the same stall in steel that's within range — let the point drill before the threads engage, and keep the speed moderate.
Can you use TEK screws in wood?
You can drive a self-drilling screw into wood, but it's the wrong tool and not what it's designed for. The drill point is made to bore steel; in wood it removes material without much benefit, and the fine machine-screw thread grips wood far worse than a coarse wood-screw thread. For wood, use a wood screw and size a pilot hole with the wood screw pilot-hole finder. Self-drilling screws are for metal-to-metal (and metal-to-wood where a steel layer is on top).
Self-drilling screw point chart
Self-drilling (TEK) screw drill point capacity chart
| Drill point | Self-drills up to | ≈ gauge / size | Typical use |
|---|---|---|---|
| #1 | 0.06″1.5 mm | 16 ga | Thin sheet / wood-to-metal (least common) |
| #2 | 0.11″2.8 mm | 12 ga | Thin to light sheet metal |
| #3 | 0.21″5.3 mm | 3/16" | Sheet to light structural — the workhorse |
| #4 | 0.375″9.5 mm | 3/8" | Structural steel and plate |
| #5 | 0.5″12.7 mm | 1/2" | Heavy plate — the category limit |
The middle column is the TOTAL steel thickness the point self-drills — all layers together, no pilot. Stay under it: a point that’s too small for the steel burns out before it penetrates, then the screw just spins and work-hardens the steel. The drill point number is separate from the screw gauge — a #10 screw can carry a #2 or a #3 point, so buy by the point.
#3 is the everyday point for sheet and light steel. Above 1/4" you’re into #5 and structural territory — follow the screw manufacturer’s data. Boundaries vary a little by brand, so check the box. Aluminium and soft metals drill easier than steel, so these steel ratings are conservative there.
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Where these numbers come from
The point-capacity ratings are cross-referenced across Simpson Strong-Tie’s technical notes, the Cold-Formed Steel Engineers Association (Tech Note TN-565c), SAE J78 (the self-drilling-screw standard), and the Grabber and ITW Buildex/Teks selection guides. They agree on the shape of it: a #3 point drills to roughly 3/16" (0.21"), a #4 to 3/8", a #5 to about 1/2" — the total steel thickness, no pilot. The exact boundary between points varies a little by manufacturer, which is why the tool is a starting point and the page says to check the box. This page covers self-drilling (TEK) screws in metal; self-tapping pilot sizing and thread-tapping are different jobs.
These are standard-convention drilling-capacity ratings for typical DIY and light-commercial self-drilling screws. Ratings vary by manufacturer and by steel grade — confirm on the product's box, and for structural or load-bearing work follow the screw manufacturer's published data.