What's inside
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What we cover
First, check whether drilling is appropriate
Copper pipe is easy to dent and easy to drill through, but that does not mean every copper line should be drilled. A hole can weaken a pressurized water line, invite corrosion, or create a leak that is difficult to reach later. Do not drill a pipe that carries water, gas, refrigerant, or another hazardous fluid unless the job has been specifically designed for it and local rules allow it. For a new branch or fitting, use the proper plumbing connection instead of drilling the pipe wall.
The steps below are for safe, non-pressurized work such as a scrap piece, a decommissioned line, or a purpose-made project. Confirm the pipe is empty and disconnected before starting. If you cannot verify what the pipe carries, do not drill it.
Why copper pipe flattens
A drill bit pushes against the pipe as it cuts. Thin-walled copper has little resistance to that force, especially when the pipe is held in a vise or squeezed by pliers. The wall can collapse before the bit breaks through. A large bit, a dull edge, high feed pressure, or a hammer setting makes the problem worse.
The fix is to support the pipe internally and avoid crushing it externally. Use a sharp bit, moderate speed, and light pressure. The pipe should be restrained against rotation, but not clamped so hard that its round shape changes.
Choose the right tools and support
For a small hole in copper, a standard cordless drill is generally enough. Turn hammer mode off; hammering is for masonry and can deform the pipe or make the bit wander. An impact driver is a poor first choice: its pulsing action gives less control for accurate drilling and can grab or distort thin material. If you need to buy a tool, a basic variable-speed cordless drill is usually the more useful choice.
Use a sharp twist bit for small holes. For a larger, clean opening, a step bit can be easier to control, provided its size range suits the job. A hole saw is usually excessive for thin pipe and can catch suddenly. A center punch can help locate a hole, but strike it gently: a hard blow can dent the tube.
For support, use a close-fitting wooden dowel, hardwood plug, or purpose-made pipe mandrel inside the tube. It should fit snugly without forcing the pipe outward. A scrap wood block with a shallow semicircular groove can cradle the outside. A vise with soft jaws can also work if tightened only enough to stop the pipe moving.
Support and bit options
| Option | Best use | Trade-off |
|---|---|---|
| Snug wooden dowel inside pipe | Small holes in accessible, straight tubing | Cheap and effective; it must fit closely and be removable |
| Grooved wood cradle | Keeping round pipe steady on a bench | Easy to make, but does not support the inner wall |
| Sharp twist bit | Small holes, roughly 1/8 to 1/4 inch | Inexpensive; can wander without a marked starting point |
| Step bit | Clean, larger holes within its cutting range | Costs more; stop at the required step to avoid enlarging the hole |
Drill the hole without crushing the tube
1. Measure and mark the location. If the hole needs to be square to the pipe, use a wraparound guide or mark a line around the tube. Put on eye protection, and secure the pipe so it cannot roll.
2. Support the inside of the pipe directly behind the planned hole. A snug dowel is enough for many small holes. If the support is loose, the copper wall can still flex inward; if it is forced in, it can stretch the pipe or become stuck.
3. Fit a sharp bit and set the drill to low or medium speed. For a typical small twist bit in copper, start around 500–1,000 rpm if the drill has a speed readout. If not, use a controlled trigger rather than running full speed. Keep the drill perpendicular to the surface.
4. Use light, steady pressure. Let the cutting edge do the work; pushing harder does not make a clean hole faster. As the bit breaks through the near wall, ease off to prevent it grabbing the far edge or catching the internal support. For a hole larger than about 1/4 inch, a small pilot hole can help, but avoid enlarging it with a sudden jump in bit size.
5. Withdraw the bit while it is turning slowly, then remove the dowel. File or deburr both edges with a deburring tool or fine file. Copper edges are sharp, and a burr can interfere with a fitting or leave a stress point.
Common mistakes and what they cause
Clamping the pipe hard in a bare vise often leaves a flat spot. If the tube starts to oval, stop and reset it with soft jaws or a grooved cradle rather than tightening further. A blunt bit tends to rub, heat the copper, and require more force; replace or sharpen it instead of leaning on the drill.
High speed and heavy pressure can make a bit skate or bite suddenly. If the bit wanders, stop, re-mark the center, and use a light punch mark or a small pilot hole. Do not use hammer mode, and do not grip the pipe with pliers close to the drilling point; their concentrated pressure can crease the wall.
For several holes or a larger opening, a metal-rated step bit may give a cleaner result than forcing a large twist bit through the tube. For one small hole, however, a sharp basic bit and a scrap dowel are often all you need.
When to stop and use another method
Stop if the pipe is connected to a system, the interior cannot be confirmed empty, the wall begins to buckle, or the bit repeatedly catches. A tube that has been flattened or badly burred may not be suitable for its intended purpose. Replace it rather than trying to hammer it back into shape, particularly if it will later carry pressure.
If the goal is to attach something to a wall near a copper pipe, do not drill the pipe at all. Locate the pipe first, then choose a suitable wall anchor or fastening point away from it. A small amount of extra setup—support inside the tube, gentle clamping, and a sharp bit—matters more than buying a high-powered drill.