Internal vs. External Star Lock Washers: Which One Ensures Maximum Grip

Publicado: January 22, 2026

Categorías: Noticias

Choosing the right small hardware can feel like a headache, especially when you’re staring at two different types of washers that look almost identical. But getting it wrong? That might lead to a loose bolt on a heavy machine or a rattling window frame. At Qewit, we’ve spent years helping global clients figure out these tiny details. Whether you are working on high-vibration engine parts or delicate electronic housings, picking between internal and external star lock washers (also called “shakeproof” washers) is a big deal for long-term stability.

What Are the Fundamental Differences Between Internal and External Star Washers?

To the untrained eye, these are just bits of metal with teeth. But those teeth are engineered for very specific jobs. Depending on whether they point in or out, they interact with your screw head and the surface material in totally different ways.

Structural Design of Tooth Orientation

The most obvious giveaway is the direction. Internal toothed lock washers, like the Arranjadoras de cerradura dentadas internas DIN 6797J or the Arranjadoras de cierre dentadas internas DIN 6798J, have their teeth tucked away inside the inner diameter. They stay hidden once the screw is tightened. On the flip side, the External Toothed Lock Washers DIN 6797A external version has teeth that fan out like a starburst. These external teeth are designed to bite into a larger surface area beyond the edge of the screw head.

Primary Mechanical Locking Principles

How do they actually work? It’s not just about being flat; it’s about the “bite.” These washers aren’t smooth—the teeth are twisted. When you torque down a bolt, these teeth flatten out and act like tiny springs. They dig into both the fastener and the material you’re bolting into. This creates a physical barrier that stops the screw from rotating backward when things start shaking.

Typical Industrial Application Scenarios

You’ll usually see internal washers used with smaller head screws—think pan heads or cheese heads—where you want a clean, flush look. They are great for electrical grounding because they scrape through paint to make a good connection. External washers are the go-to for larger hex bolts or flange bolts. Because the teeth are on the outside, they provide way more resistance against twisting forces.

Why Is Selecting the Right Star Washer Critical for Vibration Resistance?

Vibration is the silent enemy of any mechanical build. Without a lock washer, the micro-movements of a running motor or a passing train can slowly back a nut off its threads.

Prevention of Spontaneous Fastener Loosening

In high-stress environments like heavy industry or mining, a loose bolt isn’t just an annoyance; it’s a safety risk. Star lock washers are a low-cost insurance policy against this. By adding constant “spring-back” tension, they make sure the threads stay tight even when the whole assembly is under a lot of “shaking” stress.

Maintenance of Consistent Preload Tension

Keeping a bolt tight isn’t just about the initial turn; it’s about holding that “preload.” Qewit’s range of spring and lock washers is designed to keep that pressure steady over years of service. If the material expands or contracts with the heat, the twisted teeth of the star washer can flex slightly to keep the tension from dropping to zero.

Protection of Surface Coating Integrity

There is a bit of a trade-off here. Because these washers “bite,” they will scratch the surface. However, by using a specific star washer that matches your screw head size, you can make sure the damage stays hidden underneath the fastener. This is why picking the right size—from M3 all the way up to M63—is so important for keeping the rest of your parts looking good and staying rust-free.

How Do Qewit’s DIN Standards Ensure Premium Performance?

Quality in fasteners is often something you don’t notice until it fails. At Qewit, we stick to the strict “Western Style” business approach, which means we don’t cut corners on the specs.

Compliance With Precise International Specifications

We provide a huge range of products that follow the DIN 6797 and DIN 6798 standards. These aren’t just random numbers; they mean every washer has the right thickness, the right tooth angle, and the right hole size to fit your bolts perfectly. Whether it’s the “J” type (internal) or “A” type (external), the dimensions are spot on every time.

Superior Material and Finish Options

Environment matters. If you’re building something for a wet, outdoor site, you’ll want our hot-dip galvanized or stainless steel options. If it’s for a high-strength car engine, you might need Geomet or Zinc Flake coatings that handle heat and salt without the risk of hydrogen embrittlement. We offer everything from basic carbon steel to specialized alloys.

Rigorous Quality Assurance Testing

We don’t just take the factory’s word for it. Our team in China runs every batch through a gauntlet of tests—tensile strength, salt spray for corrosion, and Vickers hardness. We can even provide full 3.1 certification or PPAP reports if your project is for something high-stakes like aerospace or automotive manufacturing.

Which Configuration Provides the Maximum Grip for Your Project?

At the end of the day, you have to make a call. The “best” washer is simply the one that fits your specific bolt head and the space you have to work with.

External Star Washers for High Torque

If you have the room, go for the external version (DIN 6797A). Because the teeth are further away from the center of the bolt, they have more “leverage” to stop rotation. It’s the same reason a long wrench is easier to use than a short one. These are perfect for big hex bolts where you need a lot of grip.

Internal Serrated Washers for Compact Spaces

Sometimes, you’re working in a tight spot, or you’re using a countersunk screw that needs to sit flat. In those cases, the DIN 6798J is your best friend. The teeth stay inside the perimeter of the screw head, so they won’t snag on other parts or look messy on a finished product.

Optimized Selection Based on Material Hardness

You also need to think about what you are bolting into. Star washers work best when the washer is harder than the surface it’s biting into. If the material is too hard, the teeth might just flatten out without digging in. If it’s too soft, they might chew up the material. That’s why checking the hardness—like our 140HV or 200HV ratings—is key before you start the job.

Preguntas frecuentes

Q1: Can I reuse a star lock washer after I’ve taken the bolt out?

A: It’s usually better to grab a new one. These washers work by physically deforming (bending and biting). Once they’ve been squashed flat once, the teeth lose some of their springiness and “bite”. For a critical connection, always use a fresh washer.

Q2: Why should I use an internal star washer for electrical grounding?

A: Paint and coatings are great for stopping rust, but they are terrible for electricity. The sharp teeth of an internal star washer are perfect for digging through that paint layer to reach the bare metal, making sure your ground connection is solid.

Q3: Will these washers cause my parts to rust?

A: Because they scratch the surface, they can create a spot for rust to start if you aren’t careful. That’s why we offer coatings like Zinc Plated (480h to 720h salt spray resistance) to help protect the connection even after the teeth have done their job.