Sheet metal screws are some of the most versatile fasteners in construction and manufacturing — they fasten metal to metal, metal to wood, and metal to plastic. But the main types of sheet metal screws–self-tapping screws and self-drilling screws–are frequently confused, and picking the wrong type means either a stripped hole or a broken bit. This guide explains the differences between all sheet metal screw types and shows how to choose the right size and installation method for your project.

Self-Tapping vs. Self-Drilling: What's the Difference?

The most important distinction in the sheet metal screw category is between self-tapping screws and self-drilling screws. These two terms are often used interchangeably, but they describe fundamentally different fasteners.

Self-tapping screws cut their own threads into a pre-drilled pilot hole. Self-tapping screws often require a pilot hole to be drilled first, then the screw cuts (taps) mating threads as it is driven.

Self-drilling screws, also called Tek screws, feature a drill point — similar to a twist drill bit — at the tip. Self-drilling screws don't need a pilot hole because the tip drills through the material and the threads tap behind it in a single operation. Use an impact driver for self-tapping screws in thicker materials; self-drilling eliminates the pre-drill step entirely.

Types of Sheet Metal Screws

Type A

Type A sheet metal screws have spaced threads (coarser pitch) and a sharp point. They are designed for use in thin sheet metal, resin, plywood, and similar materials. The sharp point makes starting easy without a pilot hole in very thin stock. Thread forming screws like Type A displace material rather than removing it.

Type B

Type B screws have fine threads and a blunt point. The finer thread pitch increases thread engagement per inch of depth, providing stronger holding power in thicker materials. Thread cutting screws like Type B have serrations or a cutting slot at the tip that removes material as the screw advances.

Type 17

Type 17 screws combine fine threads with a cutting slot near the tip. The slot allows the screw to clear waste material as it cuts through harder substrates. Thread cutting screws reduce driving torque in thick or dense materials where thread forming would require excessive force.

Sheet Metal Screw Sizes

Sheet metal screws are available in a range of gauge sizes. Common sizes run from #0 through #14 in gauge. The #10 screw has a 0.190" diameter and is one of the most widely used sizes for metal roofing sheets, HVAC ductwork, electrical boxes, and general metal fabrication. Smaller gauges (#6, #8) suit lighter-gauge sheet metal; larger sizes (#12, #14) are used in heavier stock, structural loads, and replacement connections.

When determining sheet metal screw size, consider both material thickness and the required holding strength. Sheet metal screw size is determined by the metal gauge and the load requirement — thicker metal and heavier loads require larger diameter and longer screws. For help reading gauge and length callouts, see how screws are measured. Pilot holes for thicker materials are essential to avoid deflecting the screw or overloading the drive head.

What Size Hole for a #8 Sheet Metal Screw?

For a #8 self-tapping screw, the pilot hole size depends on the material. In 22-gauge sheet metal, a 9/64" pilot hole is standard. In thicker 16-gauge material, a 5/32" pilot hole is more appropriate. Using too small a pilot hole increases driving torque and risks breaking the screw or stripping the drive; too large a hole reduces thread engagement and holding power. Always use a proper drill bit sized to the screw gauge and material thickness.

Can You Screw Directly Into Sheet Metal?

Self-drilling sheet metal screws are designed to screw directly into sheet metal without any pre-drilling. The drill point at the tip acts like a twist drill, penetrating the metal before the threads engage. For very thin sheet metal (26-gauge and lighter), even self-tapping screws can sometimes be driven without a pilot hole due to the thin material. However, for 18-gauge and heavier sheet metal, using self-tapping screws without a pilot hole risks snapping the screw.

What Type of Screws Are Used for Sheet Metal?

For thin sheet metal work (HVAC, ductwork, electrical enclosures), self-tapping screws with a sharp point and coarse thread are the standard choice. For structural applications joining thicker metal, self-drilling screws eliminate the pre-drill step and are favored in roofing and metal building construction. For metal-to-wood applications, self-tapping screws with a sharp point provide better holding in the wood substrate.

Drive style matters for sheet metal work. Hex head screws are preferred in high-volume applications because the hex drive transmits more torque without stripping than Phillips or slotted drives. Hex washer head self-drilling screws are the standard for metal roofing and metal stud framing.

Drive Types for Sheet Metal Screws

For a full breakdown of recess styles, see drive types explained.

Self-Tapping Screw Installation Tips

• Drill the correct pilot hole size for the screw gauge and material thickness
• Use an impact driver for self-tapping screws in metal to reduce cam-out and maintain forward pressure
• Start screws straight — tilting in thin metal causes the pilot hole to elongate and reduces holding power
• Don't overtighten — sheet metal strips easily; stop when the head is flush and seated
• Use neoprene washers under hex heads in roofing applications to seal the hole against water infiltration

Shop Sheet Metal Screws at jakesales.com

Find self-tapping screws, self-drilling screws, and hex washer head Tek screws in all gauges and lengths at jakesales.com. Whether you're running ductwork, building metal stud walls, or fastening roofing panels, jakesales.com has the right screw in the right size for the job.