Drill Point Geometry: 118 Against 135 and Why Split Points Exist

By Bradley Taylor · August 2026

Pick up two jobber drills of the same size and look at them end on. One has a longer, more gradual point and one is noticeably blunter, with a little extra notch ground into the middle. Those are a 118 degree conventional point and a 135 degree split point, and the difference is not cosmetic. The point angle decides how the drill enters the material, how much thrust it takes to feed, what the chip looks like, and how much extra depth you need for a full diameter hole.

What the point angle actually changes

The included angle of the point sets the geometry of the whole cut. A 118 degree point is longer and more pointed. That longer point engages the material gradually, which helps the drill find center and start clean, and it suits softer materials like aluminum, brass, and mild steel where the material yields easily and long chips form without much fight. The tradeoff is that a longer cutting edge spread over a shallower angle takes more thrust to push, and in tough material that thrust turns into heat and deflection.

A 135 degree point is flatter. The cutting edges are shorter for the same diameter, the point is shorter, and the drill gets to full diameter sooner. That means less thrust for the same feed, which matters a lot in harder and tougher materials like stainless, alloy steels, and titanium. The flatter point also breaks chips into smaller pieces more readily, which those materials tend to need. The catch is that a flat conventional point does not self center well at all. Put a plain 135 degree point on a smooth surface and it will happily skate around until it finds a scratch it likes. That is exactly why the split point exists, and why you almost never see a 135 without one.

The web does not cut, and splitting the point fixes that

Here is the part that surprises people the first time they hear it. The very center of a standard drill does not cut anything. The two flutes are separated by a solid core called the web, and where the web crosses the point it forms the chisel edge. The chisel edge has no useful rake, and at the center of the drill the surface speed is essentially zero, so the material under it is not sheared away. It is smeared and extruded sideways until it reaches the lips, which is a genuinely bad way to remove metal. A large share of the total thrust on a drill is just the chisel edge bulldozing its way down.

A split point grind takes a second pair of grinds through the point and carries the cutting edges nearly all the way to center. The chisel edge shrinks to almost nothing. Now the drill cuts at the center instead of plowing, thrust drops noticeably, and the drill starts where you put it instead of wandering off to start its own project. Pair that self centering behavior with the low thrust of a 135 degree angle and you get the standard high performance jobber drill sold today.

Web thickness also changes along the length of the drill. The web is ground thicker toward the shank for rigidity, so every time a drill gets resharpened and shortened, the chisel edge gets wider and the thrust goes up. A properly resharpened drill gets the web thinned back down as part of the job. If your regrind drills push harder and cut hotter than new ones, an unthinned web is the usual suspect.

Spotting, and the angle rule that saves carbide

With a good 135 split point in a rigid setup, spotting is often unnecessary, and skipping it saves a tool change. You still want a spot drill when the drill is long relative to its diameter, when the surface is rough or sloped, or when hole location is tight enough that you cannot afford any wander at entry.

When you do spot, the angle rule matters. The spot drill angle should be equal to or larger than the drill point angle. Spot at 90 degrees for a 135 degree drill and the drill's outer corners touch the cone before the center does. The corners try to do the centering, which is exactly backwards, and on a carbide drill the corners are the most fragile part of the tool. Spot with an angle at or above the drill point angle and the drill touches at its center first, seats itself in the cone, and then brings the corners in gently. A 140 or 142 degree spot drill covers both common point angles and is a sensible default.

Point length and your depth math

The point is real length that has to come out of somewhere. A drill dimensioned to depth at the tip has not produced a full diameter hole at that depth, because the cone at the bottom is not full diameter. The point adds roughly 0.3 times the drill diameter at 118 degrees and about 0.2 times the diameter at 135 degrees. On a half inch drill that is around 0.150 or 0.100 of extra depth you need to program past the full diameter depth the print asks for. Forgetting it is a classic way to have a tap bottom out in the cone of a blind hole. The speeds and feeds calculator computes point length for you in drilling mode, along with peck guidance, and the drill size chart covers the decimal equivalents when you are converting letter and number sizes.

Deep holes and parabolic flutes

Past about four or five diameters deep, chip evacuation becomes the whole problem, and standard flutes start packing. Parabolic flute drills open up the flute space and change its curve so chips flow up and out instead of wedging, which lets you drill much deeper between pecks or skip pecking entirely with through coolant. They usually come with a 135 split point for the same thrust and centering reasons already covered. If a deep hole job has you pecking every half diameter and still hearing chip squeal, a parabolic drill is the fix, not a slower feed.

What a worn point does to your holes

Watch the chisel edge and the outer corners as a drill wears. A worn chisel edge raises thrust and heat, and worn or chipped corners are what actually ruin hole size. A drill with uneven lips or damaged corners cuts oversize and out of round, because the point wobbles and the corners scribe a bigger circle than the drill body. If your holes are running a few thousandths big, look at the drill point before you blame the machine. Two lips of equal length and equal angle, a small clean chisel edge, and sharp corners are what a good point looks like, whether it came from the grinder room or the box.

As always, this is general practice, not a spec. Prints, customer requirements, and the tool maker's published data win every argument.