Why a drill bit walks off the mark, and how to keep holes on line

01What makes a drill bit walk?

A bit walks when its point cannot grip the surface at the moment it starts turning, so the cutting edges push it sideways instead of down. Reference sources on drill geometry describe this as a basic trait of ordinary twist drills on a flat face, and they name three remedies by material: a spotting drill in metal, a brad-point bit in wood, and split points to reduce deviation. The causes below follow that logic, starting with the point itself.

1. A conventional twist point: the general-purpose point is not self-centring, so it slides on a flat face until a cutting lip catches.
2. No starting recess in metal: a hard, smooth surface gives the point nothing to seat in.
3. A metal bit used in wood: a twist bit has no spur, so nothing pins the centre while the lips start cutting.
4. The wrong bit family for the hole: large holes cut with a bit that has no guiding centre, where a hole saw on a pilot drill or a centred wood bit would track.
5. A bit that is not held straight: a tilted start puts the point on the work at an angle and risks a side load on the bit.

Each cause has its own check and fix. If you are not sure which bit families exist, the drill bits by material hub groups them by what they cut.

02Why does a standard twist bit skate on metal?

A standard twist bit skates on metal because its general-purpose point, ground to 118 degrees, is a compromise for wood, metal and plastic and is not self-centring. On painted steel, polished aluminium or a curved tube, the tip has no recess to drop into, so the first contact slides until a cutting lip catches.

Point angle also changes by workpiece. The recommended range for mild and stainless steel is 118–135 degrees, a figure given in the Wikipedia drill bit reference rather than by a bit maker, and plastics take a much sharper point. The table below shows the published ranges. A bit sharpened for one material can start poorly on another, so a set reground at home is worth checking before blaming technique.

03How does a spotting or pilot drill stop walking in metal?

A spotting or pilot drill stops walking because it cuts a small, accurately placed recess that the full-size bit then follows. Once that seat exists, the larger point has somewhere to centre instead of a flat face to slide across.

How do you confirm this is the problem?

If the bit wanders before it has cut a full circle and then drills cleanly once it is in, the start is the problem rather than the bit's sharpness. A hole that is round but in the wrong place points to the start; a hole that is oversized or ragged points to something else, such as a damaged lip.

How do you fix it?

Drill a small hole on the mark first, then open it up with the finished size. In steel, Starrett recommends a lubricant, which reduces friction wear, keeps the edge sharp and lowers the risk of breaking the bit. Edge life matters for walking because a rounded lip starts less cleanly: in a 2005 COBEM lab study of 10 mm cobalt HSS drills in alloy steel, flood coolant made drills last 52% longer on average than dry drilling, and pushing the cutting speed from 45 to 60 m/min shortened drill life considerably. The study is older and used industrial coolant, but it is still the clearest open-access figure of its kind, and it supports lubricating and slowing down on the pilot hole as well as the finished size. Starrett's speed chart gives lower speeds as diameter rises; for example it lists about 1167 rpm for a small HSS drill in mild steel. If you need the decimal size of the pilot or finished bit, the decimal drill size table lists fractional, number, letter and metric sizes side by side.

Does a center punch help?

Yes. A center punch struck with a hammer leaves a small dimple on the hole centre, so the drill point has a seat and does not wander when it starts, as McMaster-Carr's listing for a Starrett center punch describes it. The punch mark and a spotting drill work together: the punch places the centre, and the spotting drill turns that dimple into a true recess for the finished bit. The punch source is a supplier listing rather than a drilling guide from a bit maker, so it states the purpose of the tool but no depth or technique.

04Does a split-point bit stop walking?

Yes, to a large degree: a split point is ground so that the tip cuts as soon as it touches, rather than sliding until the lips catch. Starrett's catalogue describes its split-point HSS drills, ground to 135 degrees, as self-centring, easier to start, needing less feed pressure, and wandering less. That is one maker's description, but the drill bit reference makes the same general point that split points reduce deviation.

Bit makers market the same idea under their own names. DeWalt's PILOT POINT bits are sold as starting on contact, Bosch calls the tip on its cobalt bits a no-skate tip, and DeWalt's BLACK & GOLD set uses a 135 degree split point. These are manufacturer descriptions; nothing here was drilled or measured by us. A split point does not remove the need for a straight start, and on very hard or curved stock a spotting hole is still the surer route.

One common belief about these bits needs correcting. Cobalt bits are often taken to be ordinary bits with a coating, but cobalt is alloyed into the high-speed steel itself, while black oxide and titanium nitride are surface finishes. A cobalt bit with a split point helps on stainless; a coating alone does not change the point geometry that causes walking.

05How do you stop a bit walking in wood?

Use a brad-point bit. A brad-point (lip and spur) bit is a twist bit optimised for wood, and its centre spur holds the bit in line from the first turn, which is why the drill bit reference names it as the wood answer to wandering.

For larger holes, the bit family matters more than the start. Forstner bits bore clean, flat-bottomed holes, can cut on the edge of a board and can overlap holes, which a twist bit or spade bit cannot do. Spade bits are fast and rough and splinter where they exit; versions with spurs on the cutters leave a cleaner hole with less breakout. Auger bits add a self-feeding screw tip and a long spiral flute for deep holes. The trade-offs are set out in our comparison of Forstner, spade and auger bits.

Speed is a separate issue from walking, but it matters once the bit is in. Fisch and Engineering ToolBox both give lower speeds for larger Forstner bits, and an overheated bit scorches the wood and dulls quickly.

06How do you keep large holes on the mark?

For holes beyond twist-bit sizes, use a tool that carries its own centre: a hole saw on an arbor with a pilot drill, or a step drill in sheet material. A hole saw cuts only a ring, and the pilot drill in the arbor locates it before the teeth touch, so the saw cannot skate as long as the pilot stays in its hole. Milwaukee's arbor set, for example, uses a 1/4 in HSS pilot bit.

Standard bi-metal hole saws cut about 1-5/8 in deep, and Starrett notes that its deep-cut saws, at about 2 in, need arbors with an extended pilot drill. A short pilot can leave a deep saw unguided before it has cut deep enough to steady itself. When a hole saw does wander, check that the pilot is tight in the arbor and long enough for the saw, and pick the saw size from the hole saw size chart rather than by eye.

In thin sheet, a step drill cuts a range of sizes from one cone-shaped bit, and its small first step acts as its own starting hole. Our guide to step drill bits compares models for electrical boxes and panels, and for plumbing and lock work the bi-metal hole saw sets guide covers kits with arbors and pilot bits.

07Is it safe to keep drilling when a bit wanders?

No. A bit that skates can slip off the work toward your hand, and a bit forced back onto the mark at an angle is loaded sideways. Carbide and cobalt bits are harder than plain HSS but also more brittle, and the drill bit reference advises keeping the drill straight so that they do not snap. Stop, make a proper start, and then continue.

08How do you start a hole that stays on the mark, step by step?

The sequence below uses only the methods the sources name: the right bit family, a small starting hole in metal, a straight start and the right speed. Each step removes one cause from the list above.

1. Disconnect the drill Unplug the drill or remove its battery before fitting a bit.
2. Match the bit to the material Use a brad-point bit in wood, a split-point HSS or cobalt bit in metal, and a step drill or hole saw for large holes in sheet.
3. Seat the bit squarely in the chuck Tighten the chuck on the shank, using the flats on a three-flat shank where the bit has them, so the bit runs true.
4. Center-punch the mark in metal Strike a center punch on the mark with a hammer so the point has a dimple to seat in.
5. Cut a starting recess in metal Drill a small spotting or pilot hole in the punch mark, then switch to the finished size.
6. Hold the drill straight Keep the bit square to the surface as it starts, especially with brittle cobalt or carbide bits.
7. Set the speed and lubricate metal Use a lower speed as the diameter rises, following the published chart for the material, and apply lubricant when drilling steel.
8. Check the hole before going deeper Once the point has cut a full circle on the mark, continue; if it has drifted, stop and correct the start rather than forcing the bit sideways.

09How do you prevent walking on future holes?

Prevention comes down to owning the right points for the work you do and starting every metal hole on a recess. The habits below cover each cause.

• Keep a set of split-point bits for metal rather than relying on general-purpose points.
• Keep brad-point bits for wood, and Forstner bits where the hole must be flat-bottomed or overlap another hole.
• Center-punch metal and drill a small starting hole in steel, aluminium and tube before the finished size.
• Use bits with flats on the shank where you can, since three-flat and spade-style shanks are made to resist slipping in the chuck.
• Use a hole saw with a pilot drill long enough for the saw's depth.
• Use lubricant in metal to protect the edge.

For screws in wood, a pilot hole does a similar job: it guides the screw and stops the wood splitting, especially in dense species such as oak. The clearance and pilot holes chart lists sizes by screw gauge for hardwood and softwood.

10When should you replace the bit rather than change technique?

Replace the bit when the point geometry is wrong for the job or the edge is damaged, not because one hole wandered. A set of plain conventional points used mostly on steel is the clearest case: a split-point set addresses the cause directly. A cobalt bit with a chipped lip, or any bit whose lips are visibly uneven, will cut off-centre whatever the start. The fact base behind this page holds no wear limit for drill bits, so judge by how a clean, correctly started bit behaves.

The sets below are sold by DeWalt and Bosch with tips the makers describe as self-centring or as starting on contact. Specifications come from each manufacturer's product page. For a broader comparison by metal type, see our guide to bits for steel and stainless.

12What related drilling problems often appear with walking?

Walking often comes with oversized holes, snapped small bits and tapped threads that start crooked, because all three begin with a bit that did not centre. A tap drill that wanders leaves a thread off position even when the size is right; the tap drill sizes chart gives the drill for each thread, and a spotting hole first keeps it on the layout mark. Tile and glass are a separate case: glass bits are run at low speed and diamond tile tools need water cooling at all times, which corrects the idea that hard surfaces should be drilled fast. On tile, Bosch's advice for a clean start is to begin slowly with light pressure and raise pressure and speed only once the bit has bitten, with the hammer action off; Bosch, Milwaukee and Makita all limit their tile bits to rotary drilling. Our ceramic and porcelain tile bits guide covers bits that start on glaze.

For other accessory faults, the accessory problems and fixes index lists each guide by tool, and the accessory finder shows which bits a given drill and chuck accept.

13Questions readers ask