Drill bit Irwin 10501921 twist drill bit 4 mm

Irwin 10501921 twist drill bit 4 mm is a general-purpose solid twist bit designed for cordless low-RPM multi-purpose drilling. Made to work in a range of common construction and DIY materials, this 4 mm diameter bit provides precise holes for assembly, maintenance and small renovation tasks. It is intended for rotary drilling only and is compatible with standard drill chucks used on corded and cordless drills.

Advantages

The bit features a unique four-facet ground carbide tip that reduces required drilling pressure and improves centring, helping produce clean, accurate 4 mm holes. Its design minimizes walking at the start of the hole, which is particularly useful when drilling ceramic tiles and other hard surfaces. The carbide tip and solid twist geometry make the bit suitable across a broad set of materials while maintaining hole quality and tool life under appropriate drill speeds and feeds.

Suitable for

• Drilling metal sheets and light-gauge steel
• Woodworking, timber and laminated panels
• Plastics and acrylics
• Brickwork, breeze block and masonry (rotary drilling only)
• Ceramic tiles and hardened floor tiles (rotary drilling only)
• Drywall and slate

Key specifications

• Diameter: 4 mm
• Design: solid twist drill bit
• Tip: four-facet ground carbide tip for reduced pressure and accurate centring
• Suitable drilling mode: rotary (no hammer/percussion)
• Intended use: low RPM cordless and standard drills with standard chucks
• Materials: metal, wood, plastics, masonry, tiles, drywall, slate

How to use

Install the 4 mm twist drill bit securely into the drill chuck and tighten according to the drill manufacturer's instructions. Use rotary drilling mode only; do not use hammer or percussion action. Select an appropriate low to moderate RPM for the material being drilled and apply steady, even pressure—allow the carbide tip to cut without excessive force. For metals and plastics, use cutting fluid or lubricant where recommended to extend bit life and improve chip evacuation. For tiles and masonry, start at low speed to prevent walking and maintain control until the tip has established the hole.

Usage recommendations

Wear appropriate eye and hand protection when drilling. Match drilling speed and feed to the material: lower speeds for hard materials such as tiles and metal, moderate speeds for wood and plastics. Replace the bit if the tip becomes dull, chipped or if drilling performance degrades. Do not use percussion or hammer action with this bit to avoid tip damage.