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Thin brass tubing is easy to drill, but also easy to crush, snag, or leave with a ragged exit hole. For most small holes, a sharp high-speed steel (HSS) twist bit is enough. The bigger gains come from choosing a suitable diameter, supporting the tube internally, and keeping the drill steady—not buying an expensive specialty set.
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What we cover
Quick picks by job
| Job | Best bit choice | Why |
|---|---|---|
| One or a few holes, roughly 1/16–1/4 inch | Sharp HSS twist bit | Inexpensive and readily available; works well at controlled speed. |
| Repeated holes or cleaner entry | HSS bit with a 135-degree split point | Starts more reliably and is less likely to wander than a standard 118-degree point. |
| Very small holes, about 1/16 inch or less | Short, quality micro-drill bit | Less flex than a long bit; still fragile and needs careful handling. |
| Large opening in a thin wall | Step drill, if its range fits the tubing | Can make a round opening with less grabbing, but may not suit a narrow curved tube. |
Choose the bit for the hole
For ordinary holes in brass tubing, start with a standard HSS bit. Cobalt or carbide bits are usually unnecessary: brass is relatively soft, and a sharp, correctly sized HSS bit cuts it readily. Spending more makes sense if you need consistent results over many parts or want a better-ground point, not because brass requires a hard-to-find material.
A 135-degree split-point bit is a useful upgrade when the bit tends to skate on the curved surface. It begins cutting with less pressure than many conventional 118-degree bits. Even so, the tube’s curvature makes a center punch risky: a hard tap can dent or flatten a thin wall. Use a light prick mark only if needed, or make a small starting dimple with a sharp tool while the tube is well supported.
For small holes, buy short bits when available. Long bits flex more and can break if they bend or catch. A mixed HSS split-point drill bit set is a sensible general purchase, but a basic sharp HSS set is fine for occasional repairs.
Support the tubing before drilling
Thin brass tubing can collapse under vise pressure. Clamp it gently between soft jaws, wood blocks, or padded pliers, and keep the grip close to the drilling point. Do not squeeze hard enough to change the tube’s shape. For a clean hole, insert a close-fitting hardwood dowel, brass rod, or other firm backing inside the tube where you plan to drill. The backing supports the wall and reduces the burr pushed inward as the bit exits.
If the tube is too small for an internal support, clamp it between two pieces of scrap wood with a shallow groove to stop it rolling. Secure the work; do not hold a short tube in your fingers while drilling. A spinning tube can cut or burn your hand, and a bit can catch suddenly at breakthrough.
Speed and technique
Use a regular cordless drill or drill press, not an impact driver. Impact action adds little here and can make a tiny bit chatter or snap. Set the drill to its low gear and use a light, steady feed. For bits around 1/16–1/8 inch, a moderate speed—roughly 1,000–2,000 rpm—is a practical starting range. Larger bits generally need slower speed. If your drill has no speed readout, ease onto the trigger rather than running it flat out.
Keep the bit square to the tube’s surface and let its cutting edges do the work. Too much force can push the tube inward, bend the bit, or make it grab when it breaks through. Withdraw the bit occasionally to clear brass chips, especially in deeper holes. A drop of light cutting oil can help with repeated drilling, though it is not essential for one or two small holes.
For a hole larger than about 1/4 inch, avoid forcing a large twist bit through a very thin wall. It may catch at the edge and deform the tubing. A step drill can be easier to control if the tube’s shape and diameter allow the cutter to sit squarely. Check its size range and cutting geometry before buying; step drills are primarily useful on sheet and flat surfaces, not every narrow curved tube. See step drill bit sets for thin metal for options.
Common problems and fixes
The bit walks off the mark: The curved surface gives the tip little purchase. Use a split-point bit, make a small guide dimple, or drill through a simple wood guide block with a hole in the right location.
The tube dents or flattens: Reduce clamp pressure and add internal backing. If the hole is near the tube’s end, support that area especially well; unsupported ends deform easily.
The exit edge is ragged: Back the wall internally, lower feed pressure as the bit nears breakthrough, and deburr both sides with a hand deburring tool or a larger bit turned by hand. Do not use a powered large bit to clean up a delicate edge.
The bit snaps: A tiny bit may have bent because it was too long, the work moved, or the drill was pushed too hard. Use a short bit, secure the tube, and stop if the bit begins to bind. For repeated holes below 1/16 inch, a short HSS micro-drill bit set can reduce flex, but these bits remain delicate and are not a good choice for hurried hand drilling.
What to buy
For occasional work, buy a modest HSS set that includes the diameter you need and replace dull or damaged bits rather than forcing them. For repeat work, choose well-ground split-point bits in the common sizes, and keep a spare of any tiny diameter. A drill press improves consistency, but a steady cordless drill is adequate for most small holes when the tube is properly supported.
Measure the tubing’s outside diameter and wall thickness before choosing a hole size. Leave enough material around the opening to avoid weakening the tube, particularly near an end or bend. Wear eye protection, clear chips with a brush rather than your fingers, and secure the work before pulling the trigger.