Tips to Put RJ45 Connectors on Thick Ethernet Cable

Tips to Put RJ45 Connectors on Thick Ethernet Cable 

Written by Don Schultz, trueCABLE Senior Technical Advisor, Fluke Networks Copper/Fiber CCTT, BICSI INST1, INSTC, INSTF Certified

“Thick Ethernet” is not some sort of new type of Ethernet cable. What we mean by “thick” is literally that...thick. Fat. Big around. Sometimes you need to make it thinner. Will a diet of celery and lettuce get results? For you, perhaps. For your cable...nope. A pair of electrical lineman’s pliers will though.

Here is a quick video of the ovalization process actually taking place. I suggest you watch the video and read the rest of this blog, as both have something to offer.

The Problem

The ANSI/TIA 568.2-D specification and further the IEC 60603 specifies the dimensions of the outside of an RJ45 8P8C plug. There is a minimum, a maximum, and the acceptable tolerance range. This is inviolate, as deviating from the standard would result in RJ45 plugs that won’t fit into RJ45 ports. A bad thing, right? The standard does not, however, specify the interior dimensions of the RJ45 connector. That is left up to the manufacturer. Not all RJ45 plugs are designed the same on the inside, which adds to the confusion.

Ethernet cable has a maximum cable jacket diameter of 9.0mm per the ANSI/TIA 568.2-D specification, although cable that thick has no hope of fitting any RJ45 8P8C plug. You must use a different termination method such as field termination plugs, keystone jacks, or patch panels for cable that thick. Cable that is 8.0mm thick and smaller has a chance of fitting into a RJ45 plug assuming it is designed to accept a cable up to that thickness. However, the rear end of the RJ45 plug will be rectangular, not circular. This leads to frustration getting the Ethernet cable seated inside.  

The Solution

First, be sure your Ethernet cable and RJ45 plug are actually designed to fit and work together.  They might not be. This takes research, such as found in Selecting the Correct Connector.

Once you find the correct combination you are still not out of the woods. Your cable may still be difficult to get into the RJ45 connector. The way to get around this issue is to “ovalize” the last 1/2” of the Ethernet cable jacket just prior to insertion into the RJ45 plug housing. This involves using the right tool, and a certain degree of care. Careful ovalization will not damage your Ethernet cable.

The general rules around ovalization:

  • Only ovalize as much as necessary to shape the end of the cable to fit the rectangular hole in the RJ45 plug
  • This process should be done gently
  • Do not smash the cable flat!
  • Use the oval cut-out near the nose of electrical lineman’s pliers, such as these:

electrical lineman’s pliers

Parting Thoughts

You can be certain that any Ethernet cable thicker than 7.30mm will require ovalization, regardless of how the RJ45 connector is designed. This means Cat6A, and thicker outdoor shielded cable of any Category (even some of the uber thick Cat5e).

Take your time, and ovalize the end of the cable “in line” with the rear of the plug housing. Do not delay inserting the cable into the RJ45 plug, as gentle ovalization of the cable tends to spring back to circular pretty quickly. As with any technique, this may take some practice.


trueCABLE presents the information on our website, including the “Cable Academy” blog and live chat support, as a service to our customers and other visitors to our website subject to our website terms and conditions. While the information on this website is about data networking and electrical issues, it is not professional advice and any reliance on such material is at your own risk.

    1 out of ...