STAINLESS STEEL SLOTTED SET SCREWS CUP POINT DIN 438

Slotted Set Screws Cup Point DIN 438 — A cup point set screw does its job through a small, deliberate act of damage: a shallow, chamfered rim ground into the tip digs into the mating shaft as the screw is tightened, creating a mechanical indentation that resists rotation and axial slip far more effectively than a flat face bearing on the same surface would. That bite makes it the go-to choice for locking pulleys, collars, gears, and cams onto shafts in general machinery, conveyor systems, and drive assemblies wherever a positive, low-cost grip is needed and a small mark on the shaft is acceptable. Grade choice hinges on what's being clamped and where: A2 is perfectly adequate for general workshop and machinery use, but A4 becomes the sensible choice where the shaft assembly sits in a washdown, marine, or chemically exposed environment, since the cup point's small indentation is itself a stress-concentration point where corrosion can start and progress if the base material isn't sufficiently resistant. The governing standard, DIN 438, is the slotted-drive version of this fastener type — it fixes the thread, point profile and slot dimensions, and it's driven with a flat-blade screwdriver, which suits recessed or hard-to-reach locations where a hex key can't get a straight approach as easily as a screwdriver can. Sizing starts with matching the diameter to the shaft and the tapped hole in the collar or hub, then setting length so the point projects enough to bite the shaft without bottoming out excessively in the tapped hole — too short and the point won't reach the shaft; too long and the screw runs out of thread engagement before it seats. Where the shaft surface is finished, hardened, or must not be marked, the flat point version is the better fit; where a pre-drilled locating dimple exists in the shaft, a cone point gives more precise, repeatable positioning than the cup point's freeform indentation.

FAQs
Is a cup point set screw reusable in the same spot?
It can be reinstalled, but repeated tightening in the same location deepens the existing indentation rather than creating a fresh bite, so holding power on reinstallation may be somewhat reduced compared with the first fitting — repositioning slightly, where possible, restores full grip.

Why choose a slotted drive over a hex socket set screw of the same point type?
A slotted drive suits locations where a flat-blade screwdriver has better access than a hex key, or where the assembly is otherwise built around slotted fasteners for consistency; a hex socket set screw generally allows more torque to be applied in confined spaces where a screwdriver has limited leverage.

How deep should the screw seat into the tapped hole?
Deep enough that the point fully engages the shaft and the screw carries adequate thread engagement in the collar or hub, without bottoming out against the shaft before the head or slot face is flush — the correct length depends on the collar's wall thickness and should be confirmed for the specific assembly.

What happens if the wrong point type is fitted for the application?
A cup point on a shaft expecting a cone point's locating dimple will only contact a single ridge of the indentation rather than a full conical seat, giving looser, less repeatable positioning — always match point type to whether the shaft is plain, hardened, or pre-drilled.