Sheet Metal Screw Size Chart: Gauge, Length & Pilot Holes
#8 sheet metal screw with a 9/64" pilot hole. Step up to #10 for material thicker than 18 gauge. Use Tek (self-drilling) screws to skip the pilot hole entirely on metal-to-metal joints.
You're knee-deep in a washer repair, HVAC install, or auto body panel job, and the old screw is gone. The spec sheet is nowhere. You need to know: what gauge screw fits this metal, what length do I need, and does it need a pilot hole? This chart answers all three.
Sheet Metal Screw Gauge Size Chart
Sheet metal screws use the same gauge system as other sheet metal fasteners — higher number means larger diameter. The outer diameter (OD) is the thread crest; the minor diameter is the root, and the pilot hole must match that.
| Gauge | OD (in) | OD (mm) | Thread/in (Type AB) | Pilot Hole (in) |
|---|---|---|---|---|
| #4 | 0.112 | 2.84 | 24 | 3/32" |
| #6 | 0.138 | 3.51 | 20 | 7/64" |
| #8 ★ | 0.164 | 4.17 | 18 | 9/64" |
| #10 | 0.190 | 4.83 | 16 | 11/64" |
| #12 | 0.216 | 5.49 | 14 | 3/16" |
| #14 | 0.250 | 6.35 | 14 | 7/32" |
★ Most common gauge for general-purpose sheet metal work. Pilot hole diameters for Type AB screws in 20–22 gauge steel.
Pilot Hole Size by Sheet Metal Gauge
The same screw gauge drilled into different metal thicknesses needs different pilot holes. Thinner metal (higher gauge number) is softer and needs less removal; thicker metal needs a slightly larger hole to avoid stripping.
| Screw Gauge | 26–24 ga (thin) | 22–20 ga | 18–16 ga (heavy) |
|---|---|---|---|
| #6 | No.44 (0.086") | No.40 (0.098") | 7/64" (0.109") |
| #8 | No.36 (0.106") | 9/64" (0.141") | No.29 (0.136") |
| #10 | No.30 (0.128") | 11/64" (0.172") | No.22 (0.157") |
| #12 | No.24 (0.152") | 3/16" (0.188") | No.16 (0.177") |
Screw Length Selection
Sheet metal screw length is measured from the underside of the head to the tip (unlike flat-head wood screws, which are measured from the top of the head). For secure thread engagement, you need at least 3 full thread pitches past the far surface.
Practical rule: screw length = combined material thickness + 3× thread pitch. For a #8-18 screw, pitch = 1/18" ≈ 0.056". Three pitches ≈ 0.17". So fastening two layers of 22-gauge steel (0.030" each) needs a screw at least 0.030 + 0.030 + 0.17 = 0.23" — a 1/4" or 3/8" screw works fine.
Standard available lengths for #8 and #10 sheet metal screws run: 1/4", 3/8", 1/2", 5/8", 3/4", 1", 1-1/4", 1-1/2", 2". Longer is not automatically better — excessive thread past the far side can snag wires, ducts, or body liners.
Point Types: A, B, AB, and Tek
| Type | Tip | Thread | Best For |
|---|---|---|---|
| A | Sharp | Coarse | Thin soft metals, old HVAC |
| B | Blunt | Fine | Heavy gauge, non-ferrous |
| AB ★ | Sharp | Fine | General purpose — most common |
| Tek 1–5 | Drill flute | Fine | Metal-to-metal, no pilot needed |
The Tek point number (1 through 5) tells you the maximum combined steel thickness the drill tip can penetrate before the threads engage. Tek 1 handles up to 3/16" combined; Tek 5 handles up to 1/2". Use the wrong Tek number and the threads will try to engage before the hole is fully drilled — the screw strips or breaks.
Identify Your Fastener Now
Don't know the gauge? Measure the outer diameter with calipers, enter it in our identifier tool, and get the exact designation in seconds.
Open Identifier →Head Types for Sheet Metal Screws
Head type controls how the screw sits and how much material it can pull down. For sheet metal work there are four practical options:
- Hex washer head — the universal choice for HVAC and structural sheet metal. The integral washer distributes load and prevents pull-through. Driven with a nut driver or impact; no chance of cam-out.
- Pan head (Phillips or Torx) — lower profile than hex washer; used where clearance is tight (appliance interiors, panel seams). Torx drive reduces cam-out risk.
- Flat/countersunk head — sits flush or below surface. Used in auto body panels where the sheet needs to be painted flat.
- Truss head — extra-wide, low-profile head for high pull-through resistance in thin gauge. Common in electrical enclosures and lightweight metal doors.
Material and Coating Guide
The screw material must be compatible with both the metal substrate and the environment. Mismatched metals cause galvanic corrosion — the screw slowly dissolves, the joint fails.
| Application | Metal | Coating |
|---|---|---|
| Interior HVAC ductwork | Low-carbon steel | Zinc or bright |
| Outdoor / coastal | 304 or 410 SS | None (self-protecting) |
| Appliance panels | Low-carbon steel | Zinc or black oxide |
| Auto body (galv. steel) | 410 SS or zinc-plated | Must be galv. compatible |
| Aluminum sheet | 18-8 SS or aluminum | Avoid steel (galvanic) |
Quick Application Reference
For the three most common repair scenarios:
HVAC ductwork — #8 × 1/2" hex washer head, Type AB, zinc plated. Drill 9/64" pilot through both layers. Three screws per seam, minimum. Self-drilling Tek 1 if you're running lots of ductwork — saves time on hundreds of holes.
Washing machine / dryer access panel — match what came out. Most use #10 × 1/2" pan head Phillips or Torx (newer machines). If the original is stripped, replace with #10 × 1/2" hex washer for better grip. Drill 11/64" pilot if needed.
Auto interior trim panels — usually #6 × 3/8" pan head Phillips into thin clip-on brackets. Do not over-tighten — snap torque on thin plastic backing. If the hole is stripped, use a #8 × 3/8" instead (one gauge up, same length).
Recommended Tool
NEIKO 01407A Digital Caliper
Measures outer diameter to 0.01mm — the quickest way to identify an unknown sheet metal screw gauge or confirm your replacement matches the original.
View on Amazon →Frequently Asked Questions
What size sheet metal screws are most common?
#8 is the workhorse — it handles 26–20 gauge steel and covers most HVAC, appliance, and auto body jobs. #10 steps up for material thicker than 18 gauge or where higher pull-out strength is needed.
What pilot hole size do I need for #8 sheet metal screws?
Drill a 9/64" (0.141") pilot hole for #8 screws in 20–22 gauge steel. In 24–26 gauge (very thin), go slightly smaller — No.36 (0.106"). Self-drilling Tek screws in the same gauge need no pilot hole at all.
Can I use a sheet metal screw in wood?
You can, but the fine thread pitch grips wood fibers less securely than a coarse-thread wood screw. For metal-to-wood fastening (common in appliance repairs), it works fine. For wood-to-wood, use a wood screw.
What is the difference between Type A and Type B sheet metal screws?
Type A has coarser threads and a sharp point for thin soft metals. Type B has finer threads and a blunt tip for heavier gauge or non-ferrous. Type AB (most common today) combines the sharp point of A with the fine threads of B.
Do Tek screws replace self-tapping screws?
For metal-to-metal joints, yes — Tek screws drill and tap in one pass. But for metal-to-wood or thin plastic, a self-tapping Type AB with a pilot hole still provides better holding power than a Tek screw, which can over-ream thin materials.