A drill bit’s tip is conical, so the hole must go deeper than the flat-bottom depth you actually need — otherwise the cone leaves the hole short of full diameter. This calculates that extra point depth so you can set the right Z-depth in your program.
Point depth
Total depth shown assumes the desired flat-bottom hole depth equals the diameter; adjust below for your actual target depth.
Total depth for your hole
How it works
The point depth is the height of the cone formed by the drill’s cutting tip: point depth = (radius) / tan(point angle / 2). A standard 118° jobber drill adds roughly 0.3 times the diameter as point depth; a 90° split-point drill adds less, a 135° self-centering drill adds even less.
Program Z-depth = target flat-bottom depth + point depth. Skip this and through-holes will not break through, and blind holes will be shallower than intended at full diameter.
Common point angles
118° is the general-purpose standard for jobber drills in most materials. 135° split-point drills self-center and need less point depth, common on cordless and CNC drilling. 90° spotting and centering drills have a much shorter point and are used to start holes accurately before switching to a standard drill.
FAQ
Does point angle change cutting speed? No — SFM and RPM stay the same. Point angle only changes how much extra depth the tip needs and how aggressively it centers itself.
Why does this matter for peck drilling? Each peck retracts and re-enters; if your final peck does not account for point depth, the last peck will leave the hole short of full diameter at the bottom.
What about flat-bottom drills? Flat-bottom and end-milling-style drills have effectively zero point depth — enter 180° or treat point depth as zero.
Related Guides
Feeds & Speeds Calculators · G-Code & CNC Calculators · Cutting & Tooling Calculators