Most machinists learn to use drill bits before they learn what's actually happening at the point. That works fine until something goes wrong — a hole comes out oversize, a bit breaks without warning, or a regrind produces a bit that still doesn't cut. At that point, knowing the names and functions of each part of the bit is the difference between diagnosing the problem and guessing at it.
This is the anatomy of a standard HSS jobber twist drill — the most common type in machine shops and the baseline for everything else in the drill bit family.
The Point
The point is everything at the tip of the drill — the collection of geometry that does the actual cutting. Several distinct elements make up the point, and each one does a specific job.
The two main cutting edges of the drill, running from the chisel edge outward to the outer corners. These are the edges that shear material. On a standard 118-degree included-angle drill, each lip runs at 59 degrees from the drill axis. On a 135-degree split-point drill, the angle is shallower. The lips must be equal in length and height — any asymmetry produces oversized holes.
The short, flat edge at the absolute center of the point that connects the two cutting lips. The chisel edge does not cut cleanly — it scrapes and extrudes material by a combination of compression and shear. A narrow, properly-formed chisel edge minimizes thrust. A wide, worn chisel edge massively increases the axial force required to drill, causes walk at entry, and is the primary driver of drill thrust in worn bits.
The angle formed between the two cutting lips when viewed from the side. Standard for general-purpose HSS drills is 118 degrees. Sharper angles (90–100 degrees) are used for softer materials like aluminum and plastic. Flatter angles (135 degrees) are used for harder materials and are standard on split-point geometry. The point angle affects how aggressively the drill centers itself and how much axial force is required at entry.
The relief ground behind each cutting lip that allows the edge to bite into the material rather than rub against it. Proper relief for a general-purpose HSS jobber is 8 to 12 degrees. Too little relief and the drill rubs, heats, and dulls instantly. Too much relief and the cutting edge is fragile and chips under load. Relief angle decreases slightly toward the drill center to maintain edge strength where the cutting speed is lowest.
An optional modification to the standard point geometry that grinds away the chisel edge and creates two additional small cutting edges at the center of the point. A split point — also called a four-facet point — eliminates the scraping/extrusion at the center and replaces it with actual cutting. The result is dramatically reduced thrust, better self-centering at entry, and no need for a center punch or pilot drill. Split points are standard on better-quality HSS and cobalt drills and are the preferred geometry for CNC applications.
The Body
The body of the drill extends from the point back to the shank and contains the flutes, lands, and web that give the drill its structure and chip-clearing capability.
The helical grooves running the length of the drill body. Flutes serve two functions: they form the rake face of the cutting lips (the surface the chip slides along as it's formed), and they provide a channel for chip evacuation from the hole. Standard twist drills have two flutes. Helix angle — how steeply the flutes spiral — affects chip evacuation and cutting action. High helix angles (30–45 degrees) move chips out faster and are preferred for aluminum and soft metals. Lower helix angles are better for harder materials where edge support is more important than chip clearance.
The narrow raised sections on the outside of the drill body, one per flute, that make contact with the hole wall. Lands guide the drill and maintain hole size. A drill is nominally sized by its land diameter. Behind the land, the body is relieved slightly (body clearance) so the drill doesn't bind in the hole from the full diameter of the body making contact.
The solid core of the drill between the flutes. The web provides the structural backbone of the drill — it's what keeps the bit from snapping in torsion. Standard drills have a web that thickens toward the shank for strength. This web thickening is why a drill that has been shortened by repeated grinding eventually develops a wide chisel edge — as the point is ground back into thicker web, the chisel edge gets wider.
The Shank
The cylindrical section held in the chuck. Standard jobber drills have a straight shank equal to or smaller than the drill diameter. Straight shanks are held in keyed or keyless drill chucks. For CNC work, they're held in hydraulic chucks, shrink-fit holders, or precision collet chucks — the shank concentricity matters because any runout in the shank gets transmitted to the point.
Larger drills — typically 1/2" and above — are available with Morse taper shanks (MT1 through MT5) that fit directly into a taper socket in the drill press spindle or a taper-to-taper adapter. Taper shanks center more accurately than straight shanks in a chuck and can transmit more torque without slipping. They're the standard for production drilling of large holes.
Why This Matters for Resharpening
Every element of this anatomy is what a proper regrind restores. Worn cutting lips get refreshed. Collapsed lip relief gets re-established. Unequal lip heights get corrected. Split point geometry gets re-formed. The web doesn't change — it's a function of how much the bit has been shortened over its life — but thinning the web as part of a regrind can restore a drill that has grown a thick chisel edge from too many previous grinds.
Understanding what each part does makes it obvious why a bench grinder and a steady hand can't consistently do what a purpose-built drill grinder does. Correct lip relief, equal lip heights, and consistent point angle require controlled angles that a freehand grind can't reliably produce.
MachinistPost restores HSS drill bit geometry — cutting lips, lip relief, chisel edge, and split point — on a WinsloMatic drill grinder. Mail-in service from anywhere in the US. Back to you sharp within the week.
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