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Drilling: the feed you set is not the chip you cut
Two lips share the feed, and the point angle thins what remains. On a 118 degree drill the chip each edge forms is under half the number on the control — which is why light feeds break more drills than heavy ones.
Results
There is no surface finish model here, and that is deliberate: hole finish comes from margin condition, runout, alignment and chip evacuation, not from feed and a corner radius. Reporting a theoretical Ra with no mechanism behind it would be worse than reporting nothing. Verify against your drill manufacturer's data before cutting.
Why drilling is the least forgiving of the three
Turning and milling wear out. Drilling jams.
The chip is doubly thinned
Two lips split the feed, then the point angle spreads what remains along each edge. At 118 degrees that lands the chip near 0.43 of the programmed feed. The number on the control looks reasonable while the edge is below the thickness it can shear.
Speed falls to zero at the axis
The quoted cutting speed applies at the outer corner and drops linearly to nothing at the centre, where the chisel edge extrudes material sideways under pressure rather than cutting it. That region makes heat and thrust, not chips.
Evacuation decides the outcome
A blind hole has nowhere to send chips but back up the flutes. Pack them and the drill does not wear out, it breaks — in one revolution, with the part still on the machine. Past about three diameters deep, peck.
The point allowance is the other thing this page reports that most calculators skip. A conical tip has to travel past the nominal depth to break through, and on a 12 mm drill at 118 degrees that is about 3.6 mm — close to a third of the diameter. Left out of a cycle time estimate on a short hole, it is not a rounding error.
Every field explained in detailNow find the speed that actually costs least
The Taylor exponent for your machine, your material and your drill cannot be looked up. Two runs and some counting will give it to you.
RUN 1 — HIGHER SPEED
RUN 2 — LOWER SPEED
COSTS
Optimization
Both runs must use the same drill, the same feed and the same wear criterion. Speeds need at least 20% separation — two points close together will not fit a stable slope.