Set Screw Point Style Selection Guide
Set screws are fully threaded fasteners with no head—they thread into a tapped hole until the point contacts and locks against the mating surface, typically a shaft. The point style determines how the set screw grips the shaft: how much holding force it develops, whether it damages the shaft surface, and whether the shaft can be repositioned after installation. Choosing the wrong point style is a common cause of shaft slippage, excessive shaft damage, and premature loosening under vibration. This guide covers the six standard point styles and when to use each.
In This Guide:
- Cup Point
- Cone Point
- Flat Point
- Oval Point
- Dog Point
- Half-Dog Point
- Nylon Tip
- Comparison Summary
- DIN Standards Reference
- FAQ
Cup Point (Most Common)
The cup point has a circular rimmed recess at the tip that bites into the shaft surface when tightened. The rim of the cup concentrates the seating force into a small annular ring, digging into the shaft and providing strong resistance to both rotational and axial movement. Cup point set screws are the default choice for most shaft-locking applications and represent the majority of set screw usage.
- Holding power: High (highest of all point styles)
- Shaft marking: Moderate to significant ring indentation
- Repositionability: Limited — cup marks the shaft
- Best for: Fixed-position shaft collars, pulleys, sprockets, knobs, and anywhere the assembly is permanent or shaft damage is acceptable
- Standards: ASME B18.3 (inch), DIN 916 (metric)
Cone Point
The cone point is a sharp conical tip that penetrates into a pre-drilled conical seat in the shaft, or digs directly into the shaft surface when used without a prepared seat. Cone point set screws provide the highest resistance to axial (end-thrust) loading when a matching conical seat is machined into the shaft. Without a pre-drilled seat, the point digs into the shaft surface but is difficult to precisely reposition.
- Holding power: Very high (especially with mating conical seat)
- Shaft marking: Deep conical pit
- Repositionability: None practical — permanent installation
- Best for: Permanent assemblies requiring maximum axial holding force, adjustable pivot points where a matching seat is machined, and safety-critical locking applications
- Standards: ASME B18.3, DIN 914
Flat Point
The flat point has a flat, ground end perpendicular to the screw axis. It seats against the shaft surface with a flat circular contact area, distributing load over a larger area than a cup or cone and minimizing shaft deformation. Flat point set screws are used where repositioning is required, where shaft surface must be preserved, or where the set screw bears against a hard surface (hardened shaft, adjustment plate, or stop pin) that would damage a cup or cone point.
- Holding power: Moderate (lower than cup or cone due to flat contact)
- Shaft marking: Minimal flat impression
- Repositionability: Good — can be re-tightened at new position
- Best for: Adjustable stops, dial indicator stems, precision shafts that must not be marked, bearing against flat surfaces
- Standards: ASME B18.3, DIN 913
Oval Point
The oval point is a rounded (spherical) tip that seats against the shaft surface with a small curved contact area. It is gentler on shaft surfaces than cup or cone points while providing more consistent contact than a flat point on curved surfaces. Oval points are also used in applications where the set screw functions as a detent, riding in and out of a groove or depression.
- Holding power: Moderate
- Shaft marking: Light, rounded impression
- Repositionability: Good
- Best for: Detent mechanisms, soft shafts or coated shafts where surface preservation matters, and pivot applications
- Standards: ASME B18.3, DIN 915
Dog Point
The dog point has a cylindrical extension (the “dog”) protruding from the tip. The dog fits into a mating hole or slot in the shaft, providing a positive mechanical interlock rather than relying on surface friction or shaft deformation. Dog point set screws are the correct choice when positive location against a mating feature is required or when the set screw must transmit significant torque without slippage.
- Holding power: Very high (mechanical interlock, not friction-dependent)
- Shaft marking: Requires pre-drilled mating hole; no deformation
- Repositionability: Requires mating hole at each position
- Best for: High-torque shaft-to-collar connections, indexing mechanisms, and precision assemblies where position must be guaranteed regardless of vibration or load
- Standards: ASME B18.3, DIN 915
Half-Dog Point
The half-dog point has a shorter cylindrical extension than the full dog point. The shorter dog allows the set screw to sit closer to the surface and engage a shallower mating slot or flat. Half-dog points are commonly used in tooling and machine tool accessories where a keyed slot or flat on the shaft provides the mating geometry, and where the full dog’s longer extension would protrude too far.
- Best for: Machine tool accessories, toolholder retention, keyed shaft applications with shallow slots
- Standards: ASME B18.3
Nylon Tip Set Screws
Nylon tip set screws have an alloy steel body with a soft nylon insert in the tip. The nylon contacts the shaft surface with no metal-to-metal contact, eliminating shaft marking entirely. Nylon tips also provide vibration resistance—the compressed nylon acts as a spring element that maintains contact force even as the assembly vibrates. They are not a high-holding-force option; the nylon deforms under high load and the screw can slip if over-torqued.
- Holding power: Moderate (vibration-resistant but load-limited)
- Shaft marking: None
- Repositionability: Excellent — can be repositioned without shaft damage
- Best for: Chrome or polished shafts, precision ground shafts, optical equipment, instrumentation, and any application where zero shaft marking is required
- Note: Replace nylon tip after repeated tightening/loosening cycles as the nylon deforms permanently over time
Point Style Comparison Summary
| Point Style | Holding Power | Shaft Damage | Repositionable | Primary Use |
|---|---|---|---|---|
| Cup | High | Moderate | Limited | General purpose |
| Cone | Very High | High | No | Permanent, max axial load |
| Flat | Moderate | Minimal | Yes | Adjustable stops, soft shafts |
| Oval | Moderate | Light | Yes | Detents, coated surfaces |
| Dog | Very High | None (needs hole) | At drilled positions | High torque, indexing |
| Nylon Tip | Moderate | None | Excellent | Polished shafts, vibration |
DIN Standards Reference
Metric socket set screws are produced to the following DIN standards:
- DIN 913: Flat point
- DIN 914: Cone point
- DIN 915: Dog point (also covers oval point in some editions)
- DIN 916: Cup point (most widely stocked)
These DIN standards have been substantially harmonized with ISO 4026 (flat), ISO 4027 (cone), ISO 4028 (dog), and ISO 4029 (cup), but DIN designations remain commonly used in the field. Class 45H alloy steel is the standard property class for socket set screws in both inch (ASME B18.3) and metric (DIN) specifications.
Frequently Asked Questions
What is the most common set screw point style?
Cup point is the most common set screw point style. The rimmed cup bites into the shaft surface and provides high holding force for both rotational and axial loading, making it suitable for the majority of shaft-locking applications including pulleys, collars, sprockets, and handles.
What set screw point style should I use if I cannot damage the shaft?
Use a nylon tip set screw if zero shaft marking is required, or a flat point set screw if some light surface contact is acceptable. Nylon tip eliminates metal-to-metal contact entirely. Flat point distributes load over a larger area with minimal shaft deformation. Dog point eliminates surface marking if a mating hole can be drilled in the shaft.
What is the difference between a dog point and a half-dog point set screw?
A dog point has a longer cylindrical extension (dog) designed to fully engage a drilled mating hole in the shaft. A half-dog point has a shorter extension, suited to shallower mating slots or flats. Both provide mechanical interlock rather than friction-based holding. Choose dog point for deep drilled holes; half-dog for shallow slots or keyed features.
What DIN standard is a cup point set screw?
Cup point socket set screws conform to DIN 916 for metric sizes. The equivalent ISO standard is ISO 4029. Inch cup point set screws conform to ASME B18.3. All standard socket set screws—regardless of point style—are alloy steel Class 45H for inch or property class as specified for metric.
Do set screws require locking compound?
For vibration-prone applications, thread locking compound (medium strength) is recommended in addition to correct torque. Cup point set screws can loosen under sustained vibration; locking compound prevents back-out without the need for locknuts. Nylon tip set screws have inherent vibration resistance due to the compressed nylon insert.
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