Lockback knife has up/down play when closed?

[TripleF]

I bought this knife. I noticed when the blade was closed it had up/down movement. I checked the kick and, to me, it appeared to
be filed down.
I contacted the seller. He replied ALL lockback knives have up/down play when closed. I only have 2 lockback knives on me currently and one
has no play and the other has very little.

Question is, should a lockback have up/down play when closed? I thought the kick prevented this so the blade didn't touch the spring.

Couple pics below....

[cody6268]

The only ones I have with ANY play are cheap lockbacks, both from Pakistan ca. 1980s. None of my others do, from cheap to expensive knives.

[QTCut5]

Does it really matter if there's a little play when the blade is closed?
I would think it's more important that it have no movement (up/down or side-to-side) when the blade is open.

[glennbad]

I would think the kick would keep some tension on the spring in the closed position. Is the spring below the the liners in the closed position?

[btrwtr]

If the knife is well made it should not have loose up and down play when closed. As Glenn said there should be enough tension on the kick and contact point of the tang to keep the blade in place. Though not as much tension as on a well made slip joint there should still be tension.

[ea42]

I would think the problem is with the spring. If the blade is floppy or lose you have no tension in the spring, which in the case of lockbacks is putting pressure on the back lever which in turn presses against the tang. Either the spring has lost it's strength or it's too short. Another possibility, if it's a round rod inserted into the butt piece, is that it spun around. This would be caused by the spring being loosely mounted in the butt. The tension on the spring can cause it to spin so that it's pointing up rather than down which almost completely negates the tension. If that makes no sense I'll try to shoot some pics tomorrow to illustrate how this can happen.

Eric

[herbva]

Scott, the seller's answer is total B.S. I just checked all of my lockbacks, and none have any type of play in the closed position (or in the open position). Usually, when the kick is filed down a bit, it is done to adjust the position the tip of the blade sits in the well. If the blade is badly worn (usually from bad/excessive sharpening or grinding) the tip may protrude from the blade well in the closed position (dangerous for you pocket and even your leg), and can be lowered by filing the kick down a tad. (I've made plenty of these "adjustments" myself.) I'm guessing that something is seriously wrong with the knife, interfering with spring tension in the closed position. As mentioned already above, it could be major wear at the tang to spring contact point, a badly worn or damaged pin, or even a cracked spring that hasn't broken off yet. It could even be that parts have been replaced. Since you say the kick has already been filed down, that means someone has already been tinkering around with the knife for some reason.

[TripleF]

Scott, the seller's answer is total B.S. I just checked all of my lockbacks, and none have any type of play in the closed position (or in the open position). Usually, when the kick is filed down a bit, it is done to adjust the position the tip of the blade sits in the well. If the blade is badly worn (usually from bad/excessive sharpening or grinding) the tip may protrude from the blade well in the closed position (dangerous for you pocket and even your leg), and can be lowered by filing the kick down a tad. (I've made plenty of these "adjustments" myself.) I'm guessing that something is seriously wrong with the knife, interfering with spring tension in the closed position. As mentioned already above, it could be major wear at the tang to spring contact point, a badly worn or damaged pin, or even a cracked spring that hasn't broken off yet. It could even be that parts have been replaced. Since you say the kick has already been filed down, that means someone has already been tinkering around with the knife for some reason.

Thanks Herb! That's what I did - check my lockbacks, as I was hoping others would do. As I stated the one had no up/down play when closed.
I appreciate the replies. I will check all lockbacks in the future for this.
I learned something. Thanks fellas.

By the way, the kick appears to be filed away, thus the pics above.

[knife7knut]

It sounds like someone got a little overzealous with a file and took too much material off the kick.If there were wear on the the tang from the spring being harder it would wear a groove in the tang and the blade would stand proud but there would still be tension on it.JMHO

[Mumbleypeg]

Interesting topic. I have not explored this so it made me curious. I checked a number of lock backs and found none with any noticeably loose play. Several were absolutely rock solid but others could be moved with force. When the closed blade is forcibly depressed, the spring/lock becomes loose and moves. But it requires a strong push to do this. Not something I’d consider a flaw though because under normal blade closed condition it’s tight.

Based on my limited anecdotal sampling it doesn’t make any difference who made the knife. There’s variances between brands and within brands, and even on the same knife (I have a couple of double lock backs - on the same knife one blade can be forcibly depressed, the other can’t.)

Ken