3-Piece Step Drill Bit Set (4-12 / 4-20 / 4-32 mm) HSS Titanium Coated

The step drill bit set for sheet metal is a three-piece set that lets you drill holes of several diameters with a single bit in thin sheet metal, aluminum, plastic and similar materials. Each step on the conical body corresponds to a different diameter; as you advance the bit the hole grows, and you stop at the diameter you want. The set consists of three bits covering the ranges 4-12 mm, 4-20 mm and 4-32 mm, offering a total of 15 different diameters in 2 mm increments.

Many Diameters with One Bit: The Advantage of a Step Drill in AC and Refrigeration Installation

In air conditioner installation, holes for the outdoor unit bracket, cable trunking, drain passage and electrical panel all come in different diameters. With the conventional method, you have to carry a separate drill bit for each diameter and drill in sequence from small to large. A step drill reduces this job to a single bit:

• No center punch needed: The self-centering tip grips a flat sheet metal surface without slipping; there is no need to drill a pilot hole with a small bit first.
• Deburrs its own hole: The edge of the next step lightly chamfers the mouth of the hole you have drilled; on thin sheet, the edge of the hole is not left burred and sharp.
• Round, clean hole: On thin sheet, a twist drill makes triangular, distorted holes; because the step drill shaves the material with its cutting edge, the hole comes out circular.
• Enlarges an existing hole: You can easily widen a hole that was drilled wrongly or is too small by inserting the bit and moving to the next step.

Set Contents, Technical Specifications and Correct Use

• Product Code: 01 41 493
• Set Contents (3 bits): 4-12 mm (5 steps: 4-6-8-10-12) · 4-20 mm (9 steps) · 4-32 mm (15 steps) — all in 2 mm increments
• Material: HSS (high-speed steel), heat-treated
• Coating: Titanium nitride (TiN) — reduces friction, increases hardness and provides longer life than an uncoated bit
• Shank: 1/4" hex — does not spin in the chuck, fits directly into quick-change screwdrivers and cordless drills
• Flute Design: Straight flute; ejects chips during cutting
• Suitable Materials: Thin steel sheet, galvanized sheet, aluminum, copper, brass, plastic, wood and composite panels
• Packaging: Blister card, 3 bits

• 🔧 Observe the thickness limit. Step drills are for thin material; if the sheet thickness exceeds the height of one step (about 3-4 mm and above), the hole remains tapered between two diameters. Use a twist drill or punch on thick steel.
• Low speed, steady pressure. High speed burns the coating and dulls the bit. Reduce the speed especially for large diameters; let the bit cut, do not force it.
• Cutting oil extends life. When drilling metal, a few drops of cutting oil or machine oil both soften the chips and protect the coating; on aluminum it especially prevents sticking.
• Read the hole diameter from the step marking. The diameter is marked on each step; decide which step to stop at before drilling, as there is no going back once the hole is enlarged.
• Clean after use. Clear chips from the flutes and store the bit dry; the coating helps against corrosion but is not sufficient on its own.