A centre drill is a short, stiff, combination tool that has a small straight pilot point followed by a 60° tapered section. It is deliberately rigid so that it does not flex, and it is used as a preparatory operation before a longer twist drill is fed into the work.

Why it is used first:

• A long twist drill has a chisel edge at its tip and is relatively flexible, so on a flat or curved surface it tends to wander (walk) sideways before it bites, giving a mislocated or oversize hole.
• The centre drill first cuts a small, accurately located conical starting indentation (pilot hole). When the main drill enters this seat, its point is trapped on the true centre and it is guided straight down, so the finished hole is on-location and round.
• On a lathe the same 60° cone doubles as a seat for the tailstock centre, letting long bars be supported between centres.

Hence the correct statement is that it provides a pilot hole to guide the main drill.

It does not increase temperature at the cutting zone — raising temperature is undesirable and is actually reduced by coolant. It does not remove burrs and debris; burr removal is a separate deburring/reaming step performed after drilling. And it has no effect on spindle rotation, which is set by the machine's speed controls, not by the tool.