How do you evaluate a slipjoint?

JD Mandrell

JD Mandrell

Joined
Apr 20, 2001
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I am thinking of doing some testing of some slipjoints for review, but am not sure what would be good criteria?

For instance how many times can you open and close a blade before wear takes a toll? Stuff like that?

How could I measure how much pressure it takes to close the blade before and after the test period?

Thoughts?
 
Some ideas:

Obviously evaluate blade play before and after testing.
With the blade left partially open, how long does it take for the spring to go soft?

-Bob
 
I haven't heard of anyone performing tests like these, so I think you'll be starting from scratch.

Measuring how the backspring holds up to repeated opening/closing sounds like a good one.
Fit & finish is an obvious one.
Blade play (horizontal & vertical) could be measured before & after testing.
Before and after testing, assess the blade tang and determine if it lost metal or became more rounded (resulting in less positive walk & talk) due to contact with the backspring.

There are really only two moving parts (per blade) -- blade/pivot, and spring. Wear occurs in two possible places (aside from developing blade play):
1. spring losing tension
2. tang becoming rounded from contact with the spring

Peace.
 
This may sound silly, but I was thinking of pushing the back of the blade against a Postal Scale to note what number it was at when the blade "broke" and shut on it's own, then doing it again after the testing period to see if it took less force.

I'm not sure if that would be scientific enough or not, but it might give a rough way to measure?
 
If you have fishing scale (you know, a spring-loaded scale that hangs from something, with a hook on the bottom for hanging a fish), or want to get one (they're pretty cheap), you could use that.

1. Put the blade of the open knife in a vise (padded with some cloth to prevent scratching, of course) with the edge facing down.
2. Hook the scale over the handle, at a certain specific distance from the pivot.
3. Attach an open bag to the bottom of the scale, and fill it with sand until the weight of the bag makes the hinge release.
4. Record the weight.

You don't need to use the scale during the testing phase for this one, so your postal scale could work. Just use string and a bag, and measure the weight of the bag after each test.

Peace.
 
Spring tension when new (too hard to open, lazy spring). Another thing to look at is ergonomics, especially in multi-bladed knives. Are the joints flush? Do the folded blades get in the way of one that is in use? Are there sharp edges which interfere with use?
 
With quality slipjoints, I don't think wear is a major concern. I am just relating what I have heard, not going from experience, but many slipjoints have been carried and used for decades and their backsprings remain tight.

I think you should focus on bladeplay, edge retention, fit and finish, ergonomics etc... and not worry about testing wear. I think it will take too much work and not really be an issue.

Cliff Stamp does test knives to their failing point, but he doesn't open and close them over and over to see if he can get the framelock to move across the tang or make the pivot screw back out a bit.

Part of the reason we buy quality knives is because such wear is *less* of an issue (i.e. wear still exists, but we don't have to worry about backsprings going limp or framelock bars wearing out for a VERY long time).

If you wanted to review junker knives, then I think such tests would be more useful.
 
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