STAINLESS STEEL SOCKET SET SCREWS CUP POINT

Socket Set Screws Cup Point — Socket set screws with a cup point are the grub-screw form defined by DIN 916 — a fully threaded, headless screw with a small recessed cup machined into the tip, sized so its sharp circular edge bites into the mating surface as torque is applied. That combination of no head and a threaded body means the entire fixing sits within the tapped hole, which is exactly why this style exists: to lock a collar, pulley, gear, or hub onto a shaft from the side, without any part of the fastener projecting to catch on anything or interfere with a rotating assembly. The cup's edge gives genuinely useful mechanical grip against both rotation and axial slip, without needing a pre-drilled locating hole in the shaft — the general-purpose, no-preparation-needed choice among the four common point types.

Grade choice here has a mechanical dimension beyond the usual corrosion question. A2 stainless is markedly softer than hardened carbon steel grub screws, so on a hardened or high-strength shaft, an A2 cup point may deform slightly rather than bite as cleanly — worth bearing in mind on demanding drive-train applications where a hardened steel set screw might traditionally be specified. A4 offers similar relative softness to A2 but far better resistance to marine or washdown corrosion, so the corrosion-versus-hardness trade-off, not just A2-versus-A4, is the real decision on this product: stainless is the right call wherever corrosion resistance matters more than the last degree of bite into a very hard shaft.

Sizing is governed by the shaft diameter and the collar or hub it's locking: the set screw's diameter and thread need to suit the tapped hole in the hub, and enough screws (or a large enough single screw) need to be used to resist the expected torque and axial load without relying on the shaft itself to yield. Where a matching dimple or hole already exists in the shaft, a cone point makes better use of it than a cup point; where the shaft is smooth and undrilled, cup point remains the sensible default.

FAQs
How does the cup point compare with a flat point?
The cup point's sharp edge gives better holding power by biting into the surface, whereas a flat point spreads contact over a flat face without marking the surface, sacrificing grip for surface protection.

How does the cup point compare with a cone point?
A cone point provides the strongest, most positive location by seating into a pre-drilled dimple in the shaft, whereas a cup point is a general-purpose choice that grips the surface without requiring a matching hole.

Is a cup point set screw a permanent fixing, or can it be removed and repositioned?
It can be removed and repositioned, unlike a thread-locked or pinned joint, though repeated removal from the same bite point gradually reduces holding power as the original indentation wears.