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Drill screws

Drill screws have a drill-shaped cutting tip that allows pilot hole drilling, thread forming and fastening in a single operation. When driven with a power screwdriver, the tip drills through the steel sheet, and the threaded section then forms its own internal thread to secure the parts. As no pilot hole is required, they are widely used in building sheet metal work such as thin roofing, exterior walls and metal corrugated panels. Materials include carbon steel, stainless steel, and stainless steel with only the tip hardened. Besides the single-piece type without a washer under the head, there are sealing washer types to prevent rainwater ingress, such as the EPDM washer integrated type and the two-piece washer type. For fixing outdoor exterior materials, washer types are chosen for their waterproof performance.

How to choose Drill screws

  1. 1. Select the under-head length to suit the total fastening thickness

    If the under-head length of a drill screw is insufficient for the total thickness of the parts, the thread will not sufficiently engage after the cutting edge passes through, and adequate holding force will not be achieved. In the listed examples, the 4.2×13 fastens a thickness of 0.8 to 5.0 mm, while the 4.2×19 accepts up to 11.0 mm, so the upper limit changes with length. For washer types, confirm that the maximum fastening thickness is smaller even at the same length.

  2. 2. Check the drillable plate thickness

    There is a limit to the steel sheet thickness through which the drill tip can cut a hole. In plates thicker than the cutting edge length, the thread engages before the cutting edge breaks through, causing seizure or breakage. Confirm that the thickness of the base steel sheet is within the applicable plate thickness range. In the listed example, the cutting edge diameter is 2.9 mm and the cutting edge length is 3.5 mm.

  3. 3. Check consistency of length and dimensions

    The under-head length L is the length from the bearing surface of the head to the tip, which differs from the screw length. In the listed examples, L ranges from 13 to 19 mm and the screw length from 9.5 to 15.5 mm. The cutting tip portion has no thread, so judge actual thread engagement by the screw length, and also check the amount of protrusion on the back side.

  4. 4. Select diameter to determine holding force and plate thickness

    The nominal diameter affects pull-out strength and shear strength, and should be selected according to the target member and base thickness. The listed example has a nominal diameter of 4.2 mm, and its fine thread is designed to secure enough thread engagement even in thin sheets. The stripping torque (the torque at which the thread is stripped) stated in the product features is also a useful guide for tightening control.

  5. 5. Choose a washer type where waterproofing is required

    On roofs, exterior walls and other areas exposed to rain, a sealing washer type helps reduce water ingress through the screw hole. There are an integrated EPDM washer type and a two-piece washer type, and the listed examples have washer outer diameters of 11 to 12.7 mm. The head protrudes by the washer height (3.4 to 3.5 mm), so also check the installation clearance.

  6. 6. Use a bit that matches the Phillips recess number

    If the Phillips recess number does not match the driver bit size, cam-out (the bit lifting out of the recess) can deform the head or prevent thrust from being transmitted during drilling. Confirm in advance that the power tool and bit number used for installation match the Phillips recess of the product.

This guide was written by AI based on the listed products' documents and specification items. Check each manufacturer's documents before adopting.