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Aluminum is soft, but that does not make it easy to drill cleanly. Its chips can be long and sticky, and friction can make them pack into the bit’s flutes. Once that happens, the bit rubs instead of cutting, the hole gets rough, and heat builds quickly. The fix is usually a sharp bit, a controlled feed, and short pauses to clear the chips—not a more powerful drill.
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Why aluminum clogs drill bits
Aluminum tends to form continuous curls rather than the small, brittle chips you get from many steels. Those curls can wind around the bit or lodge in its flutes, especially in a deep hole. A dull bit, excessive speed, or a feed that is too light makes the problem worse: the cutting edge rubs the material, heats it, and can smear aluminum onto the bit.
Clogging is more than a nuisance. A packed bit can seize, twist your wrist, damage the hole, or break a small bit. If the bit starts squealing, stops making chips, or comes out with aluminum stuck to its cutting edges, stop and clear it rather than forcing it through.
Choose a bit suited to the hole
For ordinary holes, a sharp high-speed steel (HSS) twist bit is adequate. A standard HSS bit is inexpensive and works well for occasional drilling if it has not been dulled on masonry or steel. For frequent work, a 135-degree split-point HSS bit set is a useful upgrade: the point tends to start accurately and needs less pressure to begin cutting. Cobalt bits are generally unnecessary for aluminum; they are aimed at harder, heat-resistant metals and cost more.
For thin sheet, a step bit can make a round hole with less grabbing than a large twist bit. It is not the right choice for thick stock or deep holes. For large diameters, consider drilling a smaller pilot hole first, then opening it to size. Avoid using a badly worn bit just because aluminum is soft. A sharp, ordinary bit is better than an expensive, dull one.
| Bit type | Good fit | Trade-off |
|---|---|---|
| HSS twist bit | Occasional holes in plate, brackets, and general stock | Cheapest option; dull edges clog and heat up faster |
| Split-point HSS bit | Accurate starts and regular drilling | Costs more than basic bits, but usually reduces walking and start pressure |
| Step bit | Enlarging holes in thin sheet | Clean, controlled holes in sheet; limited depth and diameter steps |
| Hole saw | Large holes through thicker material | Needs steady control and chip clearing; can catch hard if it binds |
Set speed and feed
Use the drill’s low-speed range for larger bits and holes, and a moderate speed for small bits. As a practical starting point, try roughly 1,000–2,000 rpm for a bit around 1/8 inch, and about 500–1,000 rpm for a bit around 1/2 inch. These are starting ranges, not universal limits: bit geometry, aluminum alloy, and drill capability all matter. If the bit squeals or the workpiece gets hot quickly, reduce speed and check the edge.
Apply firm, steady pressure so the cutting lips make chips, but do not lean your full weight on the drill. Too little pressure encourages rubbing; too much can stall the drill, bend thin stock, or make the bit grab as it breaks through. A cordless drill is enough for most holes. A hammer drill should be set to drill mode with hammer action off. An impact driver can turn a hex-shank bit, but its pulsing action gives less control, so a regular drill is the better choice for clean holes and larger diameters.
Clear chips as you drill
For holes deeper than roughly one bit diameter, use a pecking cycle: drill for a few seconds, back the bit out far enough to release chips, then continue. In a deep hole, shorten the intervals if chips stop coming out freely. Pull the bit straight out while it is turning slowly or stopped; do not yank a jammed bit sideways. Brush chips off the bit with a bench brush, not your fingers, since aluminum curls can have sharp edges.
For shallow holes in thin sheet, continuous drilling may be faster, but still ease off as the bit breaks through. Support the material with scrap wood or clamp it firmly so the sheet cannot spin or flex. A sharp, pointed bit can grab at breakthrough, and a loose sheet can turn into a dangerous spinning blade.
Use lubrication when it helps
For a few shallow holes, you can often drill aluminum dry if the bit is sharp, the speed is sensible, and chips clear freely. For repeated holes, deeper holes, or a sticky cut, use a small amount of lubricant made for metalworking, such as cutting fluid for aluminum drilling. Apply a drop to the cutting area; flooding the work is not necessary. Follow the fluid label and keep it away from battery contacts and surfaces that should not be contaminated.
Do not use a lubricant if the job’s finish or later bonding process requires a clean, oil-free surface unless you can thoroughly remove the residue. If aluminum begins smearing onto the bit, stop, clean the flutes, and inspect the cutting edge. Lubricant cannot rescue a dull bit.
Avoid common failures
Clamp the work, mark the hole, and use a center punch lightly on thicker stock. On thin sheet, a deep punch mark can distort the panel; a step bit or a small pilot hole may be easier to control. Wear eye protection, because both the bit and the work can throw sharp chips. Do not brush chips away while the drill is running.
If the bit binds, release the trigger and wait for it to stop before backing it out. Do not reverse a high-speed drill while the bit is still buried unless you can control the tool and the workpiece securely. For repeated production holes, a drill press improves alignment and feed control, but it is not required for a handful of holes. A properly clamped workpiece and a sharp bit matter more than buying a larger drill.
After drilling, deburr the opening with a countersink or hand deburring tool. This removes the sharp edge without forcing a large drill bit through the hole again. The practical routine is simple: choose a sharp bit for the hole size, clamp the aluminum, drill at a controlled speed, and withdraw often enough that the flutes stay open.