Embedment depth and why anchors fail
Anchors do not fail because they are weak. They fail because the hole was wrong.
Effective embedment is measured into base material
Embedment is measured from the surface of the structural base material, not from the surface of the finish. Render, tile, screed and plaster do not count.
This is why an anchor that 'looks' deep enough can be well short of its qualified embedment.
Too shallow, and capacity collapses
Pull-out capacity is strongly dependent on embedment. A hole a few millimetres short can put an anchor materially below its published rating.
For adhesive anchors the relationship is roughly proportional to bonded area, so depth matters directly and continuously.
Too deep is also a defect
Over-drilling wastes adhesive, can break through thin elements, and may leave a void beneath the anchor that prevents correct setting.
Controlling it
A machine-set depth stop removes the operator judgement — see the depth sensor and setting drill depth.
Questions about this
What happens if the hole is slightly too shallow?
Anchor capacity depends strongly on embedment, so a hole a few millimetres short can put an anchor materially below its published rating. It is not a rounding error.
Can a hole be too deep?
Yes. Over-drilling wastes adhesive, risks breaking through thin elements, and can leave a void beneath the anchor that prevents correct setting.