Thread Locking – Why It's Essential in Bolted Assemblies

Screw Securing

Screw securing is an extremely important element of any structure using threaded connections. It should:

• operate reliably under all conditions,

• allow repeated assembly and disassembly of components,

• ensure stability in every position,

• not cause expansion of the joint,

• not weaken structural elements.

How to protect threads against self-loosening?

There are several effective methods of securing threaded connections against loosening:

• spring washers (e.g. serrated/fan washers) under the screw head,

• toothed washers,

• castellated nuts with cotter pins,

• locking screws,

• spring lock washers,

• double nut system (counter-locking).

3 Most Common Methods of Screw Securing

1. Elastic Securing

This method increases the elasticity of the bolted joint by compressing materials. As a result, it reduces the risk of self-loosening by maintaining clamping force. Examples include spring washers or high-stiffness conical washers.

2. Retention Securing

Although it does not completely prevent loosening, it prevents total separation of the joint. The following are used:

• castellated nuts,

• cotter pins,

• safety wire locking,

• threaded inserts (metal or plastic).

3. Chemical Securing – Anaerobic Adhesives

Anaerobic adhesives, such as Loctite, are among the most effective securing agents. They fill micro-gaps between threads and cure in the absence of air and in contact with metal, forming a durable, temperature-resistant joint.

Note: To achieve maximum effectiveness, thread surfaces must be clean and degreased. Some oils may interfere with the curing process.

Types of Screws and Properties of Stainless Steel

What is a screw?

A screw is a standard threaded fastening element widely used in construction and industry. Screws differ in:

• length and diameter,

• head shape,

• material (e.g. stainless steel).

What is stainless steel?

It is a low-carbon steel alloy resistant to corrosion (both atmospheric and chemical). It contains a minimum of 10.5% chromium and a maximum of 1.2% carbon, enabling the formation of an invisible chromium oxide layer. This layer is:

• self-repairing,

• durable,

• resistant to external factors.

Main characteristics of stainless steel:

• corrosion resistance,

• high temperature resistance,

• aesthetic appearance,

• easy cleaning,

• good machinability,

• recyclability,

• favorable strength-to-weight ratio.

Mechanical Properties of Screws

The core strength of a screw determines the strength of the joint. Screw materials must be sufficiently hard, ductile, and machinable. Chromium-nickel structural steels are used for screw production, and at high temperatures chromium-molybdenum-vanadium steels are applied.

The manufacturing process includes:

• cold forging,

• turning, drawing, or grinding,

• thread rolling or thread cutting.

Thread rolling ensures higher durability and wear resistance.

Typical material designations:

• C1-50, A1-50 – carbon steel,

• C4-70, C3-80 – heat-treated steel,

• A2-70 – rolled stainless steel,

• A2-80 – drawn stainless steel.

Trapezoidal Screws and Nuts

Trapezoidal screws and nuts are used where the following are required:

• positioning accuracy,

• self-locking capability,

• resistance to heavy loads.

A steel screw combined with a bronze nut provides optimal cooperation, ensuring:

• self-lubricating properties,

• quiet operation,

• resistance to overheating.

In aggressive environments, plastic nuts are used. Their durability mainly depends on thread height. In case of nut wear, an additional safety nut is applied to take over the load in the event of thread failure.

Please contact us by phone at +48 22 292 40 24 or +48 505 16 03 03, or by email (Power@PowerRubber.com) or via our contact form.