Symptoms
- Bit skids across the surface leaving scratch marks
- Bit wanders away from the marked spot
- Sparks or shiny marks on metal instead of a hole starting
- Hole starts off-center
Likely causes
- CommonNo starter mark or center punch on a hard or slick surfaceWithout a dimple, a bit has nothing to grab and slides across the surface.
- CommonDrilling metal or tile at too high a speedHigh speed on hard materials generates heat and lets the bit skate instead of cut.
- CommonWrong bit type for the materialA wood or general-purpose bit will slip on tile, glass, or hardened metal.
- PossibleDull bit tipA worn point won't bite even with the right technique.
- PossibleNot enough steady pressure at the startToo little downward force lets the spinning bit ride on top of the surface.
What to do
- Mark the exact spot and use a center punch (or a nail and hammer) to make a small dimple on metal or hard plastic.
- Start the drill at low speed with firm, steady pressure until the bit begins to cut, then increase speed.
- Confirm you're using the right bit type: masonry bits for tile/concrete, brad-point or twist bits for wood, cobalt or titanium for metal.
- On tile or glass, start at a slight angle to notch the surface, then straighten to vertical once a groove forms.
- Check the bit tip for dullness or a rounded point and swap in a sharp bit if needed.
- For very hard or slick surfaces, use painter's tape over the mark as extra grip for the starting bit.
Tools and parts
- Center punch or nail and hammer
- Painter's tape
- Correct bit for the material
Center punch toolSearch: “center punch for metal drilling”
Masonry or glass drill bit setSearch: “masonry drill bit set”
When to call a pro
If you need clean, precise holes in tile, glass, or hardened steel and keep struggling, a pro with a diamond or carbide bit and a drill press will get better results than freehand.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.