Set Screws, also called grub screws, are generally used to secure one object within or against another, typically without a nut. The most common examples are securing a pulley or gear to a shaft. Unlike standard screws, set screws apply clamping force through direct contact between the screw tip and the mating surface. The tip geometry and material determine how the screw grips, how much force it transmits, and whether it protects or mars the shaft beneath it. Set Screws are fully threaded with no head projecting past the major diameter of the screw thread.
PIC Design offers a variety of set screws with socket and slotted head types in inch and metric sizes.
Set Screw Types
Threaded the entire length with a cup-shaped indentation at one end and a socket or slotted head type at the other.
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Self-locking as the expanding nylon insert compresses against a shaft and into the thread of the holding member.
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No matter how much torque you apply to the socket head, the "Silver Grip" set screw will not scratch, mar or deform the opposing surface.
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The tip geometry determines how a set screw grips and what it does to the shaft surface beneath it. Use this table to match tip type to your application requirements.
| Tip Type | Holding Force | Shaft Protection | Repositionable? | Best For |
|---|---|---|---|---|
| Cup Point | Highest | None - marks shaft permanently | No | Standard industrial assemblies, high-torque shafts, permanent location |
| Brass Tip | Moderate | Good - no permanent marks | Yes | Precision assemblies, soft shafts, frequent repositioning |
| No-Mar | Lower | Maximum - no surface contact damage | Yes, repeatedly | Precision ground shafts, medical/semiconductor, cosmetic shaft surfaces |
| Silver-Grip | Moderate–High | Good - broad contact, no gouging | Yes | Applications needing more grip than brass tip without cup point damage |
General Rule: If the shaft will never be removed or repositioned and maximum torque transmission is required, use a cup point. If the shaft surface must be preserved, use a brass tip, no-mar, or Silver-Grip set screw, matched to the holding force required by your application.
Frequently Asked Questions
It depends on the tip type, the number of prior installations, the condition of the threads and hex socket, and how critical the application is. Here is the guidance by type:
- Cup Point Set Screws – Replace for Critical Applications; Inspect Before Reuse in Others
- Brass Tip, No-Mar, and Silver-Grip Set Screws — More Forgiving, But Inspect the Tip
PIC Design set screws are available in three body materials. For soft-tip types (brass tip, no-mar, Silver-Grip), the body material is one of the following, and the tip is a separate insert:
- Alloy Steel
- 18-8 Stainless Steel (304)
- 316 Stainless Steel
A note on tip material vs. body material: For brass tip, no-mar, and Silver-Grip set screws, the body material (alloy or stainless) governs thread strength and corrosion resistance. The tip material governs shaft protection and grip behavior. Select both independently based on your environment and surface requirements.
Size (thread diameter) is determined by the tapped hole in your component you're securing to the shaft. If you're designing from scratch and specifying the set screw hole yourself, the standard industry guideline is to select a set screw thread diameter equal to approximately one-quarter to one-third of the shaft diameter.
For metric shafts, divide the shaft diameter in millimeters by 4 to get a starting point for the set screw thread diameter. A 20mm shaft typically uses an M5 or M6 set screw; a 12mm shaft typically uses an M3 or M4.
Length should be approximately equal to the set screw's nominal thread diameter as a starting point — a 1/4-20 set screw typically runs 1/4" long as a baseline, scaled up or down from there.
- Material
- Drive Type
- Size & Thread Type
- Application Considerations (e.g. load requirements)
Although the terms are often used interchangeably, "grub screw" is sometimes specifically used to refer to the headless type.
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