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Drill an anchor hole only as deep as the anchor and its instructions require. Too shallow, and the anchor may sit proud or fail to expand properly. Too deep, and it can disappear into the wall, leave the screw unsupported, or hit something behind the surface. The right depth depends on the anchor, the material, and the screw—not just the drill bit.
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Check the anchor before drilling
Start with the anchor package or manufacturer’s instructions. Look for the required hole diameter and minimum hole depth. Anchor length alone is not enough: some anchors need extra space for dust, while others should sit nearly flush with the face of the wall.
For a basic plastic expansion anchor, the hole is usually sized to the anchor body and deep enough to accept the anchor without forcing it. Masonry screws and metal expansion anchors have their own requirements; use the specified bit diameter and depth rather than assuming a standard size. If instructions are missing, measure the anchor and screw, then check the maker’s online guidance before drilling into a critical surface.
Mark the depth on the bit
Measure the required hole depth from the tip of the drill bit and mark it with painter’s tape. Wrap the tape around the bit so its edge is easy to see while drilling. Stop when that edge reaches the wall. Tape is a simple visual stop, not a mechanical one: it can shift, and it does not prevent overdrilling if you keep pushing.
A depth-stop collar is more reliable when you have one, especially for several holes. Set it to the specified depth and test it on scrap of the same material. A drill with an adjustable depth stop can help with repeat work, but do not confuse a clutch setting with a depth setting; the clutch limits turning force, not hole depth.
Allow for the bit’s pointed tip. If the instruction calls for a certain depth, follow its measurement convention when stated. If it does not, a marked bit is a practical field method, but leave a small allowance for dust at the bottom rather than making the hole exactly the anchor’s length.
Choose the tool for the wall
In wood or drywall, a standard cordless drill is usually enough. For brick, concrete, or block, a hammer drill makes drilling faster. Use a masonry bit sized for the anchor, and switch hammer action off for wood, metal, tile, or other brittle surfaces. An SDS rotary hammer is useful for many holes in hard concrete, but it can be excessive for a couple of small anchors.
If you need a tool, a cordless hammer drill is a practical choice for occasional masonry work. A regular drill is cheaper and fine for wood and many light-duty jobs; it will simply struggle in hard masonry. Do not use an impact driver as a substitute for drilling an anchor hole. It is designed to drive fasteners, not make clean, accurately sized holes.
Depth and technique by material
Hold the drill square to the surface and begin slowly enough to keep the bit from skating. Once the hole is established, use steady pressure rather than forcing the tool. In masonry, withdraw the bit periodically to clear dust. Packed debris can make a hole feel deep even though the anchor cannot reach the bottom.
For concrete or brick, use the anchor maker’s stated depth and diameter. If dust remains, remove it with a bulb blower or vacuum; avoid blowing it out with your mouth. In hollow block, locate the part of the block the anchor is designed to grip. A standard expansion anchor may not hold well in a hollow section, regardless of hole depth.
For drywall, use an anchor made for drywall and follow its pilot-hole instructions. Some self-drilling anchors need no pilot hole, while others do. Drill only through the drywall thickness unless the anchor requires more clearance. Before drilling deeper into a wall, check for pipes and wiring, especially near outlets, switches, sinks, and radiators. A stud or pipe detector can reduce risk, though it cannot guarantee a clear path.
How depth requirements differ
| Anchor or fastener | Depth approach | Common mistake |
|---|---|---|
| Plastic expansion anchor | Match the specified hole depth; leave room for dust if required. | Using a hole too narrow or too shallow and splitting the anchor. |
| Masonry screw | Use the specified bit diameter and minimum embedment depth. | Drilling only to screw length, leaving no room for debris. |
| Toggle or hollow-wall anchor | Use the required opening size and wall-thickness range. | Assuming a deeper hole improves grip; the anchor may need a precise opening instead. |
| Sleeve or wedge anchor | Follow the required embedment and clearance below the anchor. | Ignoring the thicker base material or limited clearance behind it. |
Test the hole before fastening
After drilling, clear the dust and test the anchor by hand. It should enter as directed, without being hammered hard into an undersized hole. If it spins freely, the hole may be too wide, the material may be weak, or the anchor may be the wrong type. Do not compensate by driving a larger screw unless the manufacturer allows it.
If the anchor stands proud, remove it and check for debris or insufficient depth. Deepen the hole carefully, keeping the bit centered. If the hole is already too deep, a longer compatible anchor may work only if the instructions permit it and the wall material supports the required embedment. Otherwise, move the fixing point and fill the abandoned hole appropriately.
When to buy a depth stop or bit set
For one or two holes, tape and a correctly sized bit are usually enough. If you are installing many anchors, a drill bit depth-stop collar helps keep holes consistent. For masonry work, buy a masonry bit set only if you will use several sizes; otherwise, a single quality bit in the required diameter is less wasteful. Match the shank to your drill chuck or rotary hammer and replace a worn bit when it wanders, overheats, or takes much longer to cut.