A guide to sealing screws and shoulder screws
When it comes to precision fastening, not all screws are created equal for your application. Selecting the right type can impact everything from performance and durability to environmental protection and alignment. Two often-confused options—sealing screws and shoulder screws—serve very different functions. Understanding how they differ in design, purpose, and application is essential for making the best choice in any technical or industrial setting. In this guide, we’ll cover:
What are sealing screws?
What are shoulder screws?
Material and design differences
Common applications of sealing and shoulder screws
Pros and cons of different types
What are sealing screws?
Sealing screws, also called sealing bolts or sealing fasteners, are designed to do more than just fasten parts together—they ensure a tight, protective seal at the point of entry. Their main job is to block anything unwanted, such as fluids, air, or fine particles, from getting through the space around the screw.
By forming a secure barrier, they help maintain the integrity of the equipment or enclosure they’re used in. This added layer of protection is crucial in keeping sensitive systems operating smoothly and shielding them from potential damage caused by outside elements.
Browse our range of sealing screws
It might also help you to read our expert guide, Bolts vs. screws: What’s the difference and when to use each.
What are shoulder screws?
Shoulder screws are also known as shoulder bolts or stripper bolts. They’re a type of fastener distinguished by a cylindrical, unthreaded section between the head and the threaded portion. This unthreaded portion—the “shoulder”—is precisely machined and has a larger diameter than the threaded shaft. The shoulder allows for rotational or sliding movement of attached components, making these screws ideal when a part needs to pivot, rotate, or move with precision along a fixed axis.
Unlike fully threaded screws, shoulder screws are often used as shafts, guides, or pivot points in mechanical assemblies. The shoulder acts as a smooth bearing surface, while the threaded end fastens the screw in place. Their unique design combines the strength of a bolt with the utility of a precision shaft.
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Material and design differences
Sealing screws feature an o-ring beneath the head for secure bi-directional protection against contaminates. Contact surfaces are precision-machined to ensure the sealing element compresses uniformly. Drive styles support controlled torque to maintain seal integrity. A hex socket head screw is one example. So are torx, Phillips, and slotted drives.
Our experts have put together a guide to help you learn more: What is the best screw drive?
Shoulder screws, on the other hand, have a distinct unthreaded "shoulder" with a larger diameter than the threaded shaft. The shoulder acts as a smooth bearing surface, often used in rotating or sliding assemblies. The threaded portion simply anchors the screw, while the shoulder handles alignment or movement.
The next question is, which material should you choose? That depends on the properties that best suit your application.
Materials: At a glance
Values can vary slightly based on alloy composition, temperature, and manufacturer specification.
| Property | Stainless steel 303 | Stainless steel 316 | Titanium | Black steel | Carbon steel |
| Corrosion resistance | Moderate | Excellent | Exceptional | Poor | Moderate (if untreated) |
| Strength | Good | High | Very high | High | High |
| Weight | High | High | Low | High | High |
| Thermal resistance | Good (up to ~870°C) | Good (up to ~870°C) | Good (up to ~600°C) | Moderate (up to ~500°C) | Moderate (up to ~500°C) |
| Electrical conductivity (MS/m) Copper (reference) ~58 |
~1.25 | ~1.45 | ~1.7 | ~6–10 | ~5–10 |
| Tensile strength | Around 620 MPa | Around 620 MPa | Around 950 MPa | Around 400–550 MPa | Around 600 MPa |
| Thermal expansion | Moderate | Moderate | Low | High | High |
| Wear resistance | Moderate | High | Very high | Moderate | High |
Common applications of sealing and shoulder screws
Sealing screws are used in environments where fluid or gas ingress/egress must be prevented. Their main job is to protect internal components by maintaining a tight seal.
Sealing screws:
● Electronics enclosures: Protect sensitive PCBs from dust, moisture, or chemical exposure.
● Automotive systems: Used in engine compartments or transmissions to prevent oil or coolant leaks.
● Medical devices: Ensure sterility and prevent contamination in sealed compartments.
● Aerospace systems: Secure access points in high-altitude, pressure-sensitive environments.
● Industrial control boxes: Maintain sealing for outdoor electrical panels.
● Telecom and networking gear: Weatherproofing for outdoor installations and antenna housings.
Shoulder screws are designed for precision alignment and controlled motion. The unthreaded shoulder acts as a pivot point, guide, or shaft, while the threaded portion secures the screw in place.
Shoulder screws:
● Electronic assemblies: For compact, precise fastening with flush or recessed profiles.
● Machinery: Guiding moving parts, acting as pivot points, or aligning components.
● Automotive systems: Used for mounting brackets, moving linkages, and secure but adjustable joints.
● Construction hardware: Structural assemblies where clean, adjustable fastening is needed.
● Sealed enclosures and housings: Vented shoulder screws provide pressure equalization or venting if necessary
Pros and cons of different types
To help you decide which screw best fits your application, here’s a quick breakdown of the pros and cons of each type.
Button head seal screws
This hex-socket head screw is ideal for use in tight or limited-access spaces where precision assembly is important. Its sleek, low-profile head also makes it suitable for applications where aesthetics or clearance matter. Unlike standard fasteners with added o-rings, this screw is engineered specifically to seal effectively without damaging the sealing element.
Pros
● Effective sealing: Integrated o-ring provides reliable protection against water, dust, gases, and fluids.
● Corrosion resistant: Made from stainless steel, offering good durability in harsh environments.
● Precision-friendly: Hexagonal drive suits tight spaces and allows controlled torque in assembly.
● Versatile use: Works in both threaded and non-threaded holes; ideal for automotive, electrical, and cabinet applications.
● Purpose-built: Designed specifically for sealing—more effective than standard screws with add-on o-rings.
Cons
● Slight magnetism: May not suit EMI-sensitive environments due to partial magnetic properties
● Higher Cost: More expensive than standard fasteners
● Not Universal: Best used only where sealing is needed
Cap head screws – sealing
This cap head screw features a torx socket drive and is specifically engineered for secure, contaminant-resistant fastening. Its integrated o-ring is compressed between the screw head, the drive recess, and the mating surface for a tight, reliable seal against water, dust, gases, and other potentially damaging elements. Unlike standard screws paired with an o-ring, this design provides true sealing functionality, reducing the risk of damage to the ring or improper sealing.
Pros:
● Torx drive: Better torque control and reduces the risk of stripping
● Cap head design: robust contact surface and even pressure distribution
● Stainless steel construction: Durability and corrosion resistance
● Versatile use: Works in both threaded and non-threaded holes
● Reliable sealing: Unlike standard screws with o-rings
Cons:
● Slight magnetism: May not suit EMI-sensitive environments due to partial magnetic properties
● Higher Cost: More expensive than standard fasteners
● Not Universal: Best used only where sealing is needed
Pan head screws – sealing
This range of sealing screws with a pan head offers flexibility with three drive options: Torx, Phillips, and Slotted. Each drive type serves a specific purpose—torx drives allow fast, controlled engagement with minimal pressure; Phillips drives tolerate high torque and are easy to remove, even after being tightly installed; and slotted drives are more traditional. All screws feature a built-in o-ring that compresses between the screw head and mating surface to create a reliable, watertight seal.
Pros:
● Three drive options (Torx, Phillips, Slotted) for versatile installation needs
● Effective sealing: Integrated o-ring protects against water, dust, and gas resistance
● Stainless steel: Corrosion resistance and strength
● Vibration resistant: Performs well in vibration-prone environments without loosening
● Versatile use: Works in both threaded and non-threaded holes
Cons:
● Slotted drive offers lower torque: May slip easily
● Slight magnetism: May not suit EMI-sensitive environments due to partial magnetic properties
● Incorrect installation: May damage the o-ring, compromising the seal
Anti-vibration screw
These Phillips head shoulder screws are designed for use with VG series vibration grommets, making them a great choice for PCBs where vibration control is essential for assembled electronics. The Phillips drive provides straightforward engagement and is user-friendly, while the shoulder design allows for precise spacing or guided movement. Customers frequently pair these screws with standard hex nuts for secure and adaptable fastening in a range of applications.
Pros:
● Compatible with VG series vibration grommets for PCBs: reduces shock and vibration
● Phillips drive: Easy to install and remove
● Shoulder design: Provides alignment and spacing control
● Versatile pairing: Commonly used with metal or plastic hex nuts
● Multi-application: Suitable for electronic and mechanical assemblies
Cons:
● Limited compatibility: Specifically designed for VG grommets
● Not suited for high-load structural applications
● May require additional fasteners (e.g., hex nuts) for full assembly
Shoulder screws – hex socket head
These sealing fasteners are designed with a precisely machined cylindrical shoulder that separates the head from the threaded shaft. The shoulder acts as a bearing surface, making the screw ideal for applications that involve rotation, sliding, or precise alignment, such as mounting pins, shafts, joints, or dowels. This hex socket head screw is easily installed and removed with an Allen wrench or hex key.
Pros:
● Precision shoulder: Acts as a guide or bearing surface for movement or alignment
● Hex socket head: Allows easy installation/removal with a hex key
● Non-smooth head: Improves grip for manual handling
Cons:
● Slight magnetism: May not be ideal for sensitive electronic applications
● Not for heavy structural loads: Best used for precision motion or alignment rather than load-bearing assemblies
● Moderate corrosion resistance: Not suitable for harsh or marine environments
Shoulder – pan head screw
Also called a shoulder bolt, this pan head screw is designed with a cylindrical shaft and a machined shoulder that acts as a bearing surface. This makes it ideal for guiding motion or positioning components. The pan head features a slightly domed top with a flat bearing underside, giving it a clean, low-profile appearance that’s both functional and visually appealing and well suited for exposed or design-sensitive applications.
Pros:
● Precision shoulder: Acts as a bearing surface for alignment or controlled movement
● Pan head: Low-profile and aesthetically refined for visible or compact applications
● Slotted drive: Easy installation and removal with standard tools
● Stainless steel (303): Offers strength and moderate corrosion resistance
● Versatile use: Ideal for electronics, medical, machinery, and automotive setups
Cons:
● Slotted drive: Lower torque capacity and more prone to slipping
● Slight magnetism: May not be ideal for sensitive electronics or EMI-critical zones
● Requires clearance holes: For optimal sealing performance, extra machining may be needed
● O-ring damage risk: Improper installation or over-tightening can compromise the seal
Shoulder screws – slot head
These slot head shoulder bolts are precision-machined and designed for alignment and motion control. They feature a shoulder section—the unthreaded portion between the head and the shank—machined to exact tolerances for a reliable bearing surface. This makes them especially useful for assemblies requiring a mounting pin, dowel, shaft, or sliding motion between components. Slotted head for simple installation and removal with a standard slotted screwdriver. Best used in general-purpose settings rather than harsh environments.
Pros:
● Precision shoulder: Ensures accurate alignment and acts as a bearing surface
● Slotted head: Easily driven with a standard flat-head screwdriver
● High shear strength: Withstands lateral force in mechanical applications
● Magnetic: Not ideal for sensitive electronic applications
● Versatile applications: Electronics, machinery, automotive, and construction
Cons:
● Lower corrosion resistance: More prone to rust than other stainless variants
● Not suited for extreme environments: Best for indoor or controlled conditions
● Less secure than hex or Torx drives in torque-demanding applications
Vented shoulder cap head screws
These Vented shoulder cap head screws are designed to allow airflow or gas escape through a hole drilled along their axis. This vented design is especially important in applications where pressure equalisation or vacuum integrity is critical, making them a popular choice in HV (High Vacuum) and UHV (Ultra-High Vacuum) systems. The vent helps eliminate trapped gases in blind holes, reducing the risk of virtual leaks. The hexagonal drive enables precise torque application even in tight spaces.
Pros:
● Vented core: Allows trapped gases to escape, ideal for vacuum and sealed environments
● Precision shoulder: Ensures accurate alignment and spacing
● Hex drive: Allows for controlled installation in limited-access areas
● Cap head: Offers solid grip and distributes pressure evenly
● Corrosion-resistant: Available in 316 and 303 stainless steel for different environment needs
Cons:
● Specialised design: Not necessary for standard fastening applications
● Higher cost: More expensive than standard shoulder screws due to venting and material
● Requires precise installation: To fully benefit from the venting function
● Slight magnetism (303 SS): May not be ideal for sensitive EMI applications
Download free CADs
We offer FREE CADs available for download. If you’re not quite sure which sealing screw or shoulder screw is right for your application, our experts are always happy to advise you. Whatever your requirements, you can depend on fast despatch.
The more you know, the better. You should also read our guide, What are machine screws?
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application: 0345 528 0474.