Slipjoint lockup problems

J

John L

Joined
Oct 28, 2004
Messages
1,330
I have been having having slipjoint problems that I can't seem to solve. I get very good lockup on opening knife. My problem is on the closing lockup...very lazy. Any hints on the geometry of the spring in relation to the blade that I could be missing? I realize without pictures problem is harder to solve...but.....???
 
This really a rookie answer but maybe it might help.

  • The first suggestion is that the pivot hole may be off center providing more backspring deflection (and tension) in the open position than the closed.
  • The second suggestion is interference. If there is a bit of a burr - or a tight spot around the spots where the ricasso enters between the liners, that can cause sluggish closing. A bit of machinists blue would show this but might endanger the scales. perhaps something less staining for the same purpose.
  • Related to the above idea, if the backspring is less than perfectly flat, the liners may be 'sloped' into the opening - if that makes any sense.
Rob!

(Ask me how I learned these. :o )
 
check out chris crawford's website. he has a slip joint tutorial that answers these questions. sounds like your pivot hole is not centered.
 
Hi John, Another rookie comment. I have a different way of thinking the pivot hole is off center. When you were doing final fitting, you may(?) have taken just a little too much of the bottom (edge side) of the ricasso/pivot part of the blade. If the spring looks a slight bit deeper in the handle when the blade is closed, rather than the good lock up when it's open, it may be a tough fix. I guess what Rob said.
Good luck, Craig
 
John L said:
I have been having having slipjoint problems that I can't seem to solve. I get very good lockup on opening knife. My problem is on the closing lockup...very lazy. Any hints on the geometry of the spring in relation to the blade that I could be missing? I realize without pictures problem is harder to solve...but.....???
Click to expand...

You're right...hard to know what the problem is without seeing the bad boy. But, if I was to make a bet(assuming everthing is straight and flat and clean), I would venture a guess that the spring wasn't preloaded with enough tension.

Most production knives are pretty weak and If I would never have experienced the snap of a decent slip joint, I would have thought whimpy was normal.

Does your blade require very little effort to open? If so, there's your problem.
 
If we were talking about coil springs I'd understand all about preloading. How would I go about preloading a slip joint spring?
 
roughedges said:
If we were talking about coil springs I'd understand all about preloading. How would I go about preloading a slip joint spring?
Click to expand...

The easiest way to preload the spring is with blade in open position, rear pin in place(not peened), compress spring about 1/3 the thickness of the center pin(in the case of a 3/32" center pin that would be 1/32" compression).

Make sense?

The easiest way to compress the spring is by making the end of the center pin tapered. This will align the parts and pull the spring into place as you push the pin through. Its one of those, "it so simple why didnt I think of that" deals.
 
Again, thanks! Lately, I've been trying to find all the info I can on slip joint construction. So far, it seems like there is much less to be found then there is on other types of knives so every little bit is like diamonds to me.
 
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