Help me understand blade play when knife is closed

[kniferbro]

So I realized that my ZT 0550 has side to side blade play when closed but is solid when open and locked. I searched some threads and the general consensus is that play when closed is pretty normal. My question is why is it that there is no play when open but there is when it's closed? What changes? Hopefully someone more knowledgable can help me understand.

 

[ninjarabbi]

Probably because the lockbar isn't putting pressure on the blade tang when its closed.

 

[link2derek]

My thought exactly - the pressure created by an engaged locking mechanism helps stabilize the blade,
and you don't have that pressure when the blade is closed.

Probably because the lockbar isn't putting pressure on the blade tang when its closed.

 

[evanPGH]

Exactly what has already been said.

The only thing stabilizing the blade when closed is the tension from the pivot being screwed down combined with the tolerances that the knife is built with.

 

[mmarkh]

Try a Sebenza and you won't have blade play ever. The pivot gets tightened completely and doesn't affect blade tension at all.

 

[bladeboss]

If you have alot of patience and time, you CAN find the perfect spot where there's no play, opened or closed, still has retention, and is still smooth.

 

[OfficerCamp]

It's just a matter of trial and error sometimes. Play with lock bar tightness, pivot tightness, different lubricants, even handle screw tightness can effect blade centering/play. All can have different effects.

 

[Mikey's Deli]

So I realized that my ZT 0550 has side to side blade play when closed but is solid when open and locked. I searched some threads and the general consensus is that play when closed is pretty normal. My question is why is it that there is no play when open but there is when it's closed? What changes? Hopefully someone more knowledgable can help me understand.

Do you have a Gen 1 or Gen 2?
I am curious because I have a Gen 2 in the mail right now.

 

[kniferbro]

Do you have a Gen 1 or Gen 2?
I am curious because I have a Gen 2 in the mail right now.

I have a Gen 2.

Don't get me wrong the 0550 has the best fit and finish of any knife I have had, I love it. I just don't get how the lock bar bracing the blade from beneath stabilizes lateral movement. Also it's not that I'm able to just push the blade and it moves, it's a very dramatic slop with almost a click to it. When opened it is rock solid.

 

[GatorFlash1]

Sounds like you need to tighten the pivot, mine doesn't slop.

 

[o4tg]

Because they manufacture the knife to have 100% lock up with the stop pin while open rather than closed. It can be done, but that's a lot of man hours to put into something so trivial. The stop pin in the open and closed position, and the lock face need to have proper geometry with the pivot. It is after all a production knife, so variances are pretty normal.

Contrary to being named Zero Tolerance, it's caused by off tolerances with the stop pin. That's part of what makes the Sebenza mentioned above more expensive, since no detail is overlooked. With a good detent it realistically means Jack Ish if the stop pin properly engages while open. Compensating by tightening the pivot will just slow down the opening and smoothness.