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Well Nuts – What Are They And How Are They Used?

What Are Well Nuts?

well nuts pre-installation

A Well Nut is a removable rivet nut made of two parts. A flanged rubber portion made of EPDM Neoprene and a brass insert nut. Well nuts only require one side of the hole to be exposed so they can be used for blind fastenings.

How Do Well Nuts Work?

A well nut, also called a rubnut, rubber nut or rawlnut, is a fastener used when something needs to be connected to a surface (in most cases where only one side is available).

Installing well nuts is a simple task:

  1. A hole must be drilled into the installation material. The hole will need to be the diameter of the rubber portion of the insert.
  2. Then slide the insert into the hole so that the flange is the only portion of the nut exposed. At this point, a hole must be drilled into the material you wish to attach if it has not been drilled already.
  3. Slide a washer onto the machine screw. You want to use a washer to press down on the flange portion of the well nut. Otherwise, the well nut will try to spin during installation.
  4. Line up the two holes and insert a machine screw that matches the threading of the well nut.
  5. Begin driving the machine screw (and washer) into the threads. As the well nut tightens, the rubber portion will start to deform and pull against the back of the installation surface creating a tight strong hold.

Are Well Nuts Waterproof?well nut after being installed

One of the most common questions about well nuts is “are they waterproof?” Yes, well nuts are considered to be a waterproof fastener but it is more accurate to call them water-resistant. Well nuts create a waterproof hole by tightly pressing the deformed rubber over and into the hole to completely seal it.

There are several ways in which they will not create a waterproof seal:

  • If the Rubber on the nut dries out
    • Rubber will eventually dry out causing cracks in the nut. This can cause leaks and will eventually need to be replaced. Time to replacement will vary but salt water environments may decrease the life of the rubber.
  • If the nut becomes submerged in deep depths
    • Even though these nuts are considered to be waterproof, after a certain depth the pressure buildup on the fastener may cause the rubber to deform further and lose its seal on the hole.
  • If the screw loosens on the nut
    • Screws can loosen over time due to accidental shocks and vibrations. If the screw begins to loosen, the rubber will begin to retake its original shape and break the seal on the hole. We recommend using a threadlocker solution when installing fasteners to prevent accidental loosening.



What Are Well Nuts Used For?

Well nuts are mostly prized for their water resistant, marine grade and blind fastening properties but can be used in many different situations. These blind insert rivet nuts can be used to deter vibrations and shocks in machinery. They are also quite common in compressors and mirrors for similar reasons.

Well nuts also provide a unique quality most fasteners do not. They can act as an insulator between two materials to prevent galvanic corrosion from occurring.

Well Nuts Vs. Rivnuts

Well nut benefits:

  • Water Resistant
  • Marine Grade
  • Blind Fastening
  • Deter Negative Effects Of Vibrations and Shocks
  • Easily Replaceable

Rivnut Benefits:

  • Many Different Materials
  • Blind Fastening
  • Significantly Stronger Pull-Out Strength

*Pro Tip: While well nuts are an excellent and versatile fastener, their grip is almost exclusively based off of the deformed rubber forming a hold over and inside of a hole. Due to this, well nuts have a weaker pull-out strength than many other fasteners and this consideration should be weighed when preparing for an installation.

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