Totally agree on their value for their purpose, Craig.  I have three of them by two manufacturers, and they have been real workhorses around here.  They work perfectly to break loose a mated plug and chassis connector that have been tight for years.

However, with all of the plug pliers I have seen, the "working width" of the plastic inserts (in contact with the workpiece) is less than the width of the pliers.  The gap is close to the width of a ARC knurled retaining ring thickness for chassis mount connectors (0.110"), which is what Matt was talking about.  😭  Unless you grind off some of the steel portion off one side of the pliers, the plastic grabber will slip off the ARC knurled ring.  The closest I can get is with a Facom 410.S which has a 0.090" edge gap, and the .020" grabbing surface is just not enough to do the job of breaking it loose.  Believe me, I have tried many times with high hopes, but...

Mike  KC4TOS

On 8/19/2025 10:11 AM, Craig Cantwell via ARC5 wrote:
Before using hard tools or trying to cut the old ring, spend the $15 to $45 FOR A SET OF Cannon Plug pliers. They have good grip and the soft jaws reduce or eliminate any damage to the rings. If one has never used a set, here's what they look like. Should be a set in everyone's tool box for those hard to loosen plugs and rings.

CANNON PLUG PLIERS (CRESCENT® BRAND) from Aircraft Tool Supply



Craig
KF5JOT