A Revolution in Slip-Joint Construction


Unlike the traditional pocketknife in which the backspring rises and falls when the blade is opened and closed, the backbar of Tom Ferry’s model equipped with the Everflush Spring (top) remains flush when the blade is opened and closed. Ferry (above) works on a model with the mechanism in his shop.

The Everflush Spring takes the traditional pocketknife folding mechanism to the next level

By Lorien Arnold

As the traditional slip joint experiences a rebirth in favor among knife enthusiasts, there is increasing room for innovation in the knife’s classic, time-tested construction method.

    Enter Tom Ferry and Mike Vagnino.

    Innovators and educators, they have forged their paths in steel. Developing techniques and learning new skills, while at the same time teaching others, the two have collaborated on a concept that incorporates a generations-old method for assembling a slip joint, while bringing it into new worlds of materials and technology.

    “[An] idea evolved from the desire to engrave the backbar of slip-joint folders,” Ferry began. “The reason this was all but impossible before was that slip-joint backbars or [back]springs are heat treated, making them difficult to engrave, and, due to timing issues, [the engraving] was not easily done prior to heat treatment.

     “I had been bouncing the idea around trying to come up with a solution. One night while opening an automatic knife I noticed the internal kicker spring, which in many ways is similar in placement to a slip-joint spring. After doing some preliminary drawings, I contacted Mike for his input and assistance in developing the mechanism further. By sharing and combining forces, we cut the development time in half and have created a great working mechanism.

    “In total there have been at least five variations of the spring,” Ferry continued, “and Mike has taken the development further by creating the first multi-blade slip joint with the [new] mechanism. Mike coined the name the Everflush Spring because the backbar is always flush with the top of the handle.”

     You will notice the knives with the new spring in the accompanying photographs do not always correspond in form to the classic interpretation of the slip joint. Sporting titanium liners, bolsters and backbars, carbon fiber handles and high-alloy stainless blades, materials more common in the tactical category can be used to constitute the knives. To that end, the Everflush Spring allows for a completely solid handle configuration.

    The standard slip joint, whose backbar is a spring and must be free to move, can develop play on either side of the spring. The Everflush Spring design can incorporate pivot bearings for an action that is smooth with a crisp half stop. “The Everflush Spring is unlike common slip joints where the blade causes the spring to rise and drop as you rotate the blade from the open to closed position,” Ferry observed. “This innovation allows the opportunity for engraving of the backbar as well as eliminating the timing of the blade to the handle, as all the timing is internal.

    “[By] splitting the backbar in half, thus creating a lower spring upon which the blade rides and an upper tang stop which stays flush with the handle, the backbar does not need heat treatment. This allows a wider range of material choices and embellishing options.”

    Being intrinsic with the backbar, the lower spring diminishes the pressure exerted upon the pin, which traditionally would be used as the spring pivot. This allows the use of more exotic or fragile handle materials without fear of them cracking at the pin. In addition, the mechanism provides the potential for assembling a slip joint using threaded fasteners that allow for easy cleaning and pivot-tension adjustments.

    “The major disadvantage is that this design will not easily fit or adapt to many traditional designs,” such as folding patterns with three or more blades, Ferry noted. “The internal spring takes up more room and thereby creates issues with designing a knife for it.” Conversely, it challenges makers to devise new designs, which is always good for the knife industry.

Tango Foxtrot Knives

Ferry responded to the changing market with the creation of Tango Foxtrot Knives LLC, which he characterizes as his “new venture into the realm of semi-production knives” of his design.

    “The first knife from Tango Foxtrot is a tactical slip joint with the new mechanism, but I will also be introducing other models and types of knives in the future,” he said. “Tango Foxtrot Knives was conceived years ago but the timing never seemed to be right for me to proceed with the venture.

    “As with any new design or product, you can never be sure how it will be received by the buying public. Mike and I unveiled the Everflush Spring at the 2011 BLADE Show (www.bladeshow.com) and it was very apparent the design was a success, with both of us selling out of those knives prior to the end of the show’s first day. With the confidence of having innovated a great product, I decided to launch Tango Foxtrot Knives. The company’s first release was the prototype version of the T-1 folder at the 2011 USN Show, and again the design went over well.

“I am currently in production of the T-1 slip joint with the Everflush Spring,” Ferry maintained, “as well as designing other models of fixed blades and folders to develop a line of semi-production knives of my design. The components for the knives will be made out of shop, but all final assembly and fit and finish will be done in my shop. Most will be everyday user knives, but there will also be the occasional dressed-up model featuring my hand engraving.”

Another Level

The knife business tends to reward those who contribute to it. Moreover, there is always a connection to the past, as every maker builds upon the innovations, techniques and styles of those who came before. It is a rare cutler who introduces something completely new. It is an even rarer one who can take an innovation and bring it to the next level. There is always another level and, through Ferry and Vagnino’s innovation, the cutlery industry may be getting a peek at the next one.

    For more information on the Everflush mechanism, contact Tom Ferry at tomferryknives@q.com or www.tomferryknives.com , or Mike Vagnino at mvknives@lightspeed.net or www.mvknives.com.

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