A Slip Joint Spring question...

[Kevin Wilkins]

I have an order to make a tactical slip joint for a client in England. Locking blades are forbidden there. He wants a knife with a blade length of about 2 inches and a strong spring. What type spring dimensions would you guys suggest? I expect I'll use a stainless steel for the spring. Blade will be about 3,5 mm thick.

Thanks in advance!

[Ray Rogers]

That may be a difficult question for anyone here to answer as most of us don't make slip joints. Those that do are more likely to make a small delicate knife than one intended for tactical use.

If it were my project I think I'd make the spring fairly 'high'. In other words, the length and profile of the spring will be determined by the size and shape of the knife (assuming your design has the spring forming the back spacer). The only dimension remaining is the vertical thickness of the spring, so I'd make it a little extra meaty and then grind it down gradually until I got the kind of tension I wanted....

[Kevin Wilkins]

Thanks for the tip! If I grind the spring down from the inside, the side facing the blade when the knife is closed, then that wont change the profile of my grip! Why didnt I think of that? ;-)

I plan on making a model of this one before I start cutting metal.

Those knife laws in England are really crap. Hee in Germany I can carry almost any knife I like, except butterflys and large springers.