Screw locking


Screw locks for maximum anti‑rotation locking, even under strong vibrations and dynamic loads.


Maximum security against unscrewing

Twin‑Lock screw locking systems effectively prevent threaded connections from working loose.

Positive locking instead of friction. Unlike conventional methods, the Twin‑Lock screw locking system utilises the preload force of the joint. For that reason it is superior to conventional screw locking systems.

Method / principle

Twin‑Lock consists of two identical wedge‑locking washers, which feature radial cogs on one side and splined cogs on the other side. This leads to an increase in the preload force when the joint is released, efficiently securing the threaded connection even under strong dynamic loads and vibrations.


The use of Twin‑Lock washer pairs is recommended wherever there is a risk of threaded connections working loose. Twin‑Lock provides effective protection even under strong vibrations and dynamic loads.

Product benefits
  • Optimal locking solution under strong vibrations and dynamic loads
  • Detachable and reusable with no performance loss
  • Well‑established locking system for threaded connections
  • Can be used with screws/nuts of all property classes (up to 12.9)
  • Can often be retrofitted in use without difficulty

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

Optimum locking solution

No loosening. Even under strong vibrations and dynamic loads.

Simple and easy to assemble

Pre‑bonded washer pairs prevent errors during initial assembly and are easy to handle.

Suitable for use with lubricants

Since the locking effect relies on preload force rather than friction, anti-rotation locking is guaranteed on both dry and lubricated surfaces.

Environmentally friendly and corrosion‑resistant

With its high‑quality coating, Twin‑Lock is highly corrosion‑resistant and is completely free from Cr6.

Detailed description


Operating principle

When the nut/screw is tightened, the radial external cogs of the Twin‑Lock lock washer press positively into the contact surface. The tilt angle α of the splined cogs is greater than the pitch angle β of the screw thread.
Therefore, when the threaded connection is loosened, the preload force initially increases. In addition, the coefficient of friction of the radial cogs on the outer surfaces of the washers is much higher than the coefficient of friction on the inside with the splined cogs. In practice, the combination of the washer pairs results in reliable anti‑rotation locking, even in adverse conditions.

Twin-Lock screw locking system


Highly versatile. Twin‑Lock washers can be used for screw locking in threaded holes, countersinks and through holes and with studs. Two pairs of lock washers should be used in through holes. In addition, in slotted holes and for soft mating materials we recommend using Twin‑Lock washers with a large outer diameter. Important: Twin‑Lock must not be used on unsecured washers.

Installing the Twin-Lock screw locking system

1) Threaded holes
2) Countersinks
3) Through holes
4) Studs


Twin‑Lock put to the test

Twin‑Lock ensures that the preload is retained in the joint. The diagram below shows the high anti-rotation locking capacity of the washers. Unlike screws with no locking element (red line), the preload force remains constant over the entire load period. The blue line illustrates the increase in force required to loosen the joint after load changes (click effect).

Test parameters

  • Screw: M8 class 8.8
  • Preload: 9.1 kN
  • Clamping length: 14 mm
  • Surface coating: Delta Protekt® KL100+VH30
  • Lubrication: SAE 30 oil
Test certificate for the Twin-Lock screw locking system


Green = M8 screw with Twin‑Lock with a preload of 50 % of the yield point
Red = M8 screw without lock washer
Orange = M8 screw with conical spring washer
Yellow = M8 nut with polyamide ring
Blue = Change in preload force while the screw is loosening (click effect)

Product variants

Every project deserves a tailor-made solution.

Learn more about the product types and find the right variant for your particular application.

Twin‑Lock with standard diameter

The standard version is suitable for a wide variety of applications – including countersunk bolts.


Twin‑Lock with large outer diameter

This version is ideal for soft materials and slotted holes.


More information

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Here you will find information about successful applications and related topics.