A fully-featured toolbox is a sign that you’re serious about your job. It also means you’ve come prepared to deal with any surprises along the way. Drills and drill bits are the bread and butter of any self-respecting tradesman, and one of the first tools you’ll pick up. To create holes for placing bolts and screws or driving these fasteners into building materials, you’ll need the right type of drill and drill bits. Fortunately, there’s a variety of drills and dozens of different drill bits, both for general or specialised jobs. They’re made of different materials and come in a range of sizes and shapes to drill through all kinds of surfaces.
What are Step Drill Bits?
Step drills bits are not the average bits that you attach to drill chucks. They differ from regular drill bits in the way they are designed and how they’re used. They’re conical in shape, with a profile resembling a child’s rendering of a Christmas tree. They have ‘steps’ that widen in diameter from the drill tip or head, and gradually enlarging with each step towards the end. This allows for drilling holes of different widths from the same bit; essentially replacing a whole set of multi-purpose drill bits in different sizes. Grooves along the steps help to remove any excess materials, meaning you get a clean finish for installing fasteners.
Step bits can be attached to both handheld or bench drills, adding to their versatility. They’re mainly used in solid sheet metals, able to drill holes up to 1.5 mm of stainless steel or non-ferrous metals and alloys like aluminium, copper and brass. Larger holes, up to 5mm can be drilled into non-treated steel and thermoplastics.
Parts in a Step Drill Bit
Step drill bits consist of an angled point tip. The angle of the point varies, the larger the angle the more pressure is needed to achieve an initial tap into the material being drilled. Typical angle sizes are 118°, 130° and 135°. Extending downward from the point are two swirling split point cuts or ‘thinnings’ set opposite each other. These allow the bit to pierce into the material. To go further, step bits usually have two profiles of grooves that run the length of the bit from the first to the last step. These are equipped with cutting edges that gradually expand in width with each step.
There are two types of step drill bits based on the design of the groove, spiralled and straight step bits. The grooves help in removing any excess materials, such as metal chips while drilling. They also prevent the drill bit from overheating as it eats into the material. Steps are stepped at 90° angles from the groove profile allowing for gradual deburring as each step gets further down the material. The bit thins into a cylindrical flattened end or ‘shank’ that is attached to the drill chuck.
The number and diameter of steps vary in differently sized bits. Most step bits will have 9 individual steps, with other variants with up to 12 steps. Step size numbers are engraved into every separate step for precision drilling. Diameters are marked as gauge numbers for smaller sized bits or letters for larger bits. Diameters range from 104 gauge or 0.08mm to V or 9.6mm. The lower the gauge number and letter the bigger the drilling diameter. To cover your needs, sets of step bits in different sizes are available.
Materials
Step drill bits need to be made of the appropriate material for the surface they’re drilling into. The cheapest are ‘HSS’ or high-speed steel bits and are good for drilling into plastics or wood. Cobalt step bits have higher strength and resist heat buildup when drilling into harder materials like steel or aluminium. Titanium and oxide-coated HSS bits are less brittle, meaning they’ll drill into metals while having less wear. The most durable and sharp are carbide-tipped step bits that are used in heavy-duty drilling into concrete, tiles and brick.
Using Step Drill Bits
Smaller bits have a self-starting tip meaning you don’t need a pilot bit to get going. Larger step bits need pre-drilled holes that are equal to the width of the pointed tip. Before you start drilling make an indentation with a centre punch and hammer to allow for the point to catch and settle. Apply fluid to a smaller step bit and align the drill to the marked indentation. Drill into the material by pressing the drill trigger and applying the appropriate pressure. A smaller hole will appear. Drill through to the last step and apply fluid as needed. Replace the small step with a larger one. Drill into the material with the large step until you reach the diameter you require. Repeat the process until the hole is cleared of any burrs.
Buying Step Drill Bits
Step drill bits are sold separately or packaged in sets of two or more pieces. They are the right tool for drilling smaller holes into a range of materials, from plastics and stainless steel to masonry. Different sizes are available with visible markings. When buying, consider the materials you often use in your line of work and get the appropriate step drill bit.
