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How To Select The Right Threadlocker

For over 60 years, Loctite have been producing a variety of threadlockers suitable for a wide range of applications. As their expertise has grown, so has the demand for new and innovative product adjustments, leading to a wider range of product available. But how do you know which threadlocker is right for the job at hand?

What is a threadlocker?

A threadlocker is a liquid adhesive designed to secure fasteners from loosening between maintenance cycles. At Loctite, the threadlocker has become widely known as the “red bottle” due to its distinctive look.

Did you know that there is only 15% metal-to-metal contact in the interior of a bolted assembly and that the remaining 85% is simply air? This leads to gaps and the loosening of threaded connections.

Loctite threadlocker text on red background

Why are threadlockers important?

Loctite blue being applied to metal thread


When fasteners loosen, this can cause serious accidents and a total shutdown of a production plant. Threadlockers add an extra level of protection by defending against improper tightening, shocks and vibration, thermal expansion and corrosion.

Unlike conventional fastening methods such as double nuts and spring washers, Loctite threadlockers maintain clamping force, fill all gaps and provide an air-tight seal.

How do I select the right threadlocker for my application?

Due to the number of different shapes and sizes of threaded fasteners, a diverse range of product by viscosity, curing speed and strength means you can choose the right product for your application. To do this, simply answer these three questions.

  • What is the size of the fastener?
  • What is the required torque?
  • How often are the fasteners disassembled?

Loctite being applied to metal
Please Note: When a threaded assembly has already been assembled and torqued to the target clamp load, a wicking grade threadlocker can be used. This is also suitable for locking adjustment screws and set screws after correct position has been achieved.

Fastener Size

The Loctite threadlocker range is suitable for threaded fasteners up to M80 size, and as small as M6.

Strength Required

All Loctite threadlockers are colour coded based on the strength they exhibit once cured:

  • Low – Pink/Purple
  • Medium - Blue
  • High - Green
  • Permanent - Red

Loctite blue being added to screw thread

Frequency of Service

Based on the strength selected above, this will indicate the frequency of disassembly permitted. Low strength threadlockers are more suited to frequent disassembly, while high strength products are more common on rarely disassembled components.


For more advice on the application of Loctite threadlockers, read our How to Apply Loctite Threadlockers guide.

Your Loctite Front Line Threadlocker Range

Loctite chart showing bottles in order of adhesive strength