They resist the screw rotating backwards in its own thread, which is the usual way a set screw fails.

A plain cup point grips the shaft well and then backs off under vibration, so the joint loosens even though the bite was sound.

The teeth engage the shaft surface asymmetrically, so turning out meets more resistance than turning in.

That converts the seating contact into part of the locking system rather than just the holding system.

Manufacturers publish comparative vibration data, and the improvement over a plain cup point is substantial.

It does not replace a thread-locking method where the application is severe; it complements one.

Marginally at best - the holding mechanism is the same bite, and the serrations address loosening rather than grip.

Both styles cut into the shaft and resist rotation through that penetration.

The teeth slightly increase penetration for a given torque by concentrating load on smaller contact points.

The real gain is that the setting is still there after weeks of vibration, which in practice means the joint holds when a plain point would not.

If raw holding power is the requirement, a cone point into a spot drill gives more.

If location is the requirement, a dog point solves it outright.

Leaves a serrated impression that is more disruptive to dress out than a plain crater.

Instead of one smooth depression with a burr, the shaft carries a patterned area with multiple raised edges.

Cleaning that up takes longer and removes more material.

On shafts dismantled regularly the marks accumulate faster than with a plain point.

A machined flat confines the damage to one dressable surface and is worth adding where service is expected.

Where the shaft must stay unmarked, this style is the wrong choice entirely.

Poorly - the teeth concentrate load on small tips and sink into soft material.

In brass, aluminium and plastics the serrations embed rather than bite, and the material flows around them.

As it flows the clamping load drops and the joint loosens, which is the opposite of the intended effect.

Soft materials generally want a flat point or a soft-tipped screw with a larger contact area.

On very thin walls the concentrated load can also deform the section.

They perform best on steel shafts of ordinary hardness, which is what they are designed for.

When the joint has to be adjustable, when temperature rules adhesive out, or when both the seating and the thread need to hold.

Thread-locking adhesive needs cure time, clean dry threads and a temperature within its chemistry's range.

A knurled point works immediately on installation and is unaffected by contamination.

It also remains adjustable, whereas a cured adhesive resists every subsequent movement.

Adhesive addresses only the thread; the knurl addresses the seating as well.

In demanding machinery the two are frequently used together rather than as alternatives.

Follow the manufacturer's figure - the serrations change how the load is distributed at the point.

Teeth concentrate load on small contact areas, so penetration happens at lower torque than a plain cup point of the same size.

Over-tightening flattens the teeth, which removes exactly the feature that was paid for.

A flattened knurl behaves as a blunt cup point and offers no vibration advantage.

As with all set screws, the socket is the weak feature and a fully seated key is essential.

Reusing a screw whose teeth are visibly flattened gives none of the intended benefit.

Vibrating machinery, motor and fan hubs, and any drive that reverses.

Rotating assemblies with imbalance are the classic case, since the loosening force is continuous.

Reversing drives are worse than continuous ones, because the hub works back and forth against the seating.

Conveyors, pumps and blowers use them widely for the same reasons.

Portable and vehicle-mounted equipment benefits because of road and transport vibration.

For assemblies that are never disturbed and never vibrate, a plain cup point is cheaper and just as effective.