The Life of the Cold Knife

Is the old cold knife disappearing? Will the wire/cord crimping tool overtake other auto glass removal tools? Are violent power removal tools going to be replaced with more passive tools?

Recently I thought about who invented the cold knife and when it was first offered? It certainly had a good run. When I started in the industry, in the mid-70s, the cold knife was a major tool in my toolbox along with a hook tool and a utility knife. Wire and handles were also present, but the cold knife took the lead when it came to glued-in glass removal tools.

I figured the cold knife would be easy to research, so I began probing. There was no shortage of sites offering “auto glass removal tools” for sale, but the history of the tool was seriously lacking. The many names associated to the tool over the years caused a major problem. Cold knife, cable knife, windshield removal tool were all used interchangeably, which makes it difficult to track down.

The first cold knife

I called my friend and colleague, Bob Nilsson from Ultra Wiz who steered me to Jeff Cothery. Jeff told me that his father, Harry R Cothery, invented the cold knife based on PPG’s suggestion in the early 1960’s. He went on to invent and patent the “Hot Knife” as well, patent number 3,448,517. Unfortunately the hot knife never really took off like the cold knife did, and due to the existence of similar tools, it was unable to be patented. Jeff turned out to be a wealth of information and I want to thank him for satisfying my curiosity.

The first hot knife

Now to address the questions above.

Is the cold knife disappearing? I believe current technicians will never let it disappear completely. The cold knife took them a while to master and once they did there was never a tool that could remove the glass faster and smoother than a well sharpened cold knife.

Will the wire/cord crimping tool overcome other auto glass removal tools? With the potential for vehicle damage minimized, no physical exertion required, and providing even an inexperienced tech the ability for a safe efficient removal, they provide a lot of benefits. As people get used to seeing wire-out tools and trying them, they will increase in popularity.

Will the power removal tools be replaced with more passive removal tools? I don’t think so. Power tools are the fix when all else fails. If power tools are used incorrectly they can cause serious damage to the vehicle, but for experience techs there will always be a place in the tool box for the ultimate tool that will “get-er done”.

You have to say a few things about Harry’s cold knife invention, the long learning curve it takes to master and the effort expended using it, the cold knife, when used properly still works great. Don’t throw your cold knife away yet.