Best Drill Bit for Aluminum: Choose by Thickness and Hole Depth

For ordinary DIY holes in aluminum brackets, angle and plate, start with a sharp, bright-finish HSS twist bit. Choose a high-helix design when chip clearance is the main difficulty, or a step bit when you need several hole sizes in thin sheet.

HSS means high-speed steel. You do not need to upgrade automatically to cobalt or carbide just because you are drilling metal: Metal Supermarkets’ aluminum guidance identifies both HSS and cobalt as suitable and says carbide is usually unnecessary for this work.

The choices below are based on published specifications and application guidance, not a hands-on performance ranking. For a kit that also needs to handle steel and stainless, see our best drill bits for metal.

Ordinary holes: bright HSS twist bit

A conventional twist bit is the practical default when you need one diameter through a bracket, extrusion or plate—or a blind hole that must stop at a controlled depth. Remember that its pointed tip leaves a conical bottom, not a flat one.

A straightforward product to consider is the Dormer A113. It is an HSS jobber-length drill with a bright finish and a conventional 118° point. Dormer lists metric sizes from 0.8–14 mm and fractional sizes from 3/64–35/64 inch. The manufacturer describes its bright finish as improving chip flow and evacuation in soft, sticky alloys, including non-ferrous alloys. That makes it a sensible specification-based choice for general aluminum work. See Dormer’s A113 specifications.

Buy the exact size you need rather than a large set unless your projects genuinely require multiple diameters. Before ordering, check:

• Cutting diameter: a bolt-clearance hole and a hole for tapping threads are different sizes.
• Shank diameter: the cutting diameter alone does not establish chuck fit.
• Usable drilling depth: check the individual bit’s dimensions, not just its overall length.

For a threaded hole, choose the tap-drill size first; our 1/4-20 tap-drill guide explains that distinction.

Chip-clearance problems: high-helix HSS

If aluminum keeps packing into the flutes during deeper drilling, look for an aluminum-rated high-helix or fast-spiral HSS bit rather than simply buying a harder bit.

The useful feature is the flute geometry. Ohio Drill & Tool’s 2019 technical catalog, pages 9–10, describes its high-helix drills as having wide flutes to promote chip removal in aluminum and other soft materials, with benefits in deep-hole applications.

This is an upgrade for a particular problem, not a requirement for every shallow hole. It also does not eliminate the need to clear chips. Check that the exact bit is rated for your material and has enough usable depth; “high helix” is not a drilling-depth specification.

Thin sheet and several diameters: step bit

A step bit is the more convenient choice for enlarging holes or making several marked hole sizes in thin aluminum sheet. Its limitation is the short cylindrical section at each diameter—not the bit’s overall length.

One option is Milwaukee’s SHOCKWAVE #1, model 48-89-9241. Milwaukee lists aluminum among its applications, a 1/8–1/2-inch range with 13 steps, a 1/4-inch hex shank and 1/8-inch step thickness. It is compatible with drills as well as impact drivers. Those are fit and application specifications, not evidence that it outperforms other step bits. See the manufacturer’s product specifications.

Keep the sheet thinner than the selected diameter’s usable step length so that the next step does not enlarge the entrance before the required diameter clears the back. Do not confuse the listed flute length with the thickness it can drill at one diameter. For thicker plate, use a twist bit instead. Our step-bit guide explains the geometry in more detail.

Do you need cobalt or a titanium coating?

If you already own a sharp cobalt bit rated for aluminum, use it. But for aluminum-only DIY work, prioritize the correct diameter, sharp edges and chip clearance before paying for cobalt.

Likewise, do not choose solely by a “titanium” label or gold color. Check the exact product’s aluminum rating. Carbide becomes more relevant for production drilling with a rigid machine setup; it is less forgiving of imperfect handheld alignment, as Metal Supermarkets explains.

Make the bit cut, not rub

Clamp the work securely and wear suitable eye protection. On a drill press, remove the chuck key, keep guards in place, tie back long hair, and avoid gloves, jewelry and loose clothing. Reduce pressure as the bit breaks through. These precautions follow CCOHS drill-press guidance, which also recommends lubricating metal drilling and clearing deep holes frequently.

Use a cutting fluid labeled for aluminum and follow its application instructions. Withdraw the bit periodically when needed to clear chips; stop rotation before brushing away tangled swarf. Pecking and light cutting fluid help prevent aluminum from sticking to the bit, according to Metal Supermarkets.

Set speed from the bit maker’s guidance for the alloy and diameter. If the bit spins without producing chips, stop and inspect the edge, lubrication and chip clearance rather than adding pressure. Remove the exit burr after drilling.