Carbon Steel Hex Sems Screws External Tooth Lock Washer Zinc Plated Grade 8.8 For Industrial Equipment
What problem do sems screws solve?
Two problems actually. First, assembly speed. Picking up a screw and a separate washer takes extra seconds. Every second counts on a production line. Second, lost washers. When you loosen a regular screw, the washer falls off. It drops into the machine. It rolls across the floor. It disappears. A sems screw keeps the washer captive. It stays right where it belongs.
How do they work?
The washer is already fitted under the screw head. It sits there permanently. It cannot fall off. You grab one part, not two. Drive the screw in. The washer is exactly where you need it. Every time.
Which washer type do you need?
| Washer type | Solves this problem |
|---|---|
| Spring washer | Screws loosening from vibration |
| Flat washer | Soft material damage from uneven clamping |
| External tooth lock washer | Rotation under heavy vibration |
| Internal tooth lock washer | Snagging on wires or cables |
| Double washer (spring + flat) | Both vibration and pressure distribution issues |
Head styles
| Head type | Best use |
|---|---|
| Phillips pan head | General assembly, most common |
| Hex head | Higher torque, wrench or socket drive |
Stocked head styles include hex socket head, Phillips pan head and hex washer head. Custom profiles like truss head, flat countersunk head and terminal sems screws for electrical connection can all be made to order.
Material selection
| Material | Best for |
|---|---|
| 304 stainless steel | Outdoor, wet, corrosion protection |
| 316 stainless steel | Marine, salt water |
| Zinc plated carbon steel | Indoor, cost effective |
Common applications
- Electronics assembly – fast, no loose parts
- PCB mounting – consistent clamping force
- Control panels – reliable connections
- Industrial equipment – vibration resistance
- Automotive parts – anti loosening
- Marine enclosures – corrosion resistance
- HVAC units – quick installation
Quality
ISO 9001 and ISO 10012 certified. Every batch inspected. Washer retention tested.
Custom
Non-standard size or head marking? Send drawing or sample. OEM orders welcome.
YH Fastener has been manufacturing precision fasteners since 1998. Our product range includes sems screws, self tapping screws, machine screws, and custom fasteners. We are ISO 9001 and ISO 10012 certified. Every batch is inspected before shipping. We sell factory direct and ship to over 60 countries.
- Pre assembled washer – one part instead of two
- Spring washer for anti vibration
- External tooth lock washer for high vibration
- Double washer (spring + flat) for demanding jobs
- Phillips pan head and hex head styles
- Stainless steel and carbon steel options
- Metric M3 to M6, Grade 8.8 to 12.9
FAQ
It comes from "screw and washer assembled." Over time it became sems. Now it is the standard term for pre assembled screw and washer combinations.
Regular screw and washer are two separate parts. Sems screw is one piece. The washer cannot fall off. Assembly is faster. No lost washers.
External tooth lock washer or spring washer. Both resist loosening from vibration. External tooth gives you more bite into the surface.
Yes. Choose stainless steel 304 or 316. Both resist corrosion.
Metric M3, M4, M5, M6. Lengths 6mm to 30mm. Custom sizes available.
Yes. Send us your drawing or sample. OEM orders accepted.