Flex in the Lock-Back

tecstrat · #1

I just got a new Spyderco Delica 4 in the mail today :) and I was doing the normal BS- checking the lock up (pulling up and down close to the handle) which felt tight and I was happy! Then I took the blade to the cutting board and did a push cut thru a straw with the tip of the blade and as I applied pressure to the tip against the board I noticed some flex, quite a bit of flex actually! :confused:

I checked ALL of my Spyderco knifes with a lock back design and they all suffer from this affliction- Delica, Endura, Dragonfly...I am sure Im not the only one thats felt this. Some of them have never been used and I THOUGHT all of them had a tight lock up until I applied downward pressure to the tip. When you do this you will feel flex in the lock. Is it possible that this is the pressure transferring to the spring and that is what you actually feel flexing and moving with the blade?

I am a BIG Spyderco fan! But I have to admit I was disappointed when I realized this. I guess I always thought that the blade should be rigid once locked open...maybe I am wrong.

Design flaw or nature of the design?

I would love to hear if any of you find the same symptom on your Spyderco blades with the lock back design. Please try this with one of your blades and let me know if you feel it too...

Gunslinger · #2

Wow, your right. I checked out my lockbacks after reading your post and noticed that my endura 4s have this flex. you can feel the spring pressure pushing it back. I can feel it in the stretch, pacific salt, and police3, but not as bad.

tecstrat · #3

Gunslinger wrote:Wow, your right. I checked out my lockbacks after reading your post and noticed that my endura 4s have this flex. you can feel the spring pressure pushing it back. I can feel it in the stretch, pacific salt, and police3, but not as bad.

Yeah, I was shocked too!

Frapiscide · #4

My guess is that it's inherent to the design. When you put pressure on the blade, it exerts force towards the back of the knife. That would then move the lock bar and push against the lock spring holder and cause a gap, resulting in flex?

tecstrat · #5

Frapiscide wrote:My guess is that it's inherent to the design. When you put pressure on the blade, it exerts force towards the back of the knife. That would then move the lock bar and push against the lock spring holder and cause a gap, resulting in flex?

That seems like a reasonable explanation. Is it a bad thing?

Blerv · #6

It's common in all back-locks. Some don't have as much but it's still there. I think the least I have experienced is with my Adventura with an all steel backing.

http://www.spyderco.com/forums/showpost ... ostcount=2

and

http://www.spyderco.com/forums/showthread.php?t=38899

It doesn't make it any weaker, just different.

JimP · #7

Frapiscide wrote:My guess is that it's inherent to the design.

+1

All my back locks have this shifting when under pressure, it has been talk about a fair bit on these forums, all my knives have proven to be very safe and secure, albeit a little disconcerting at first.

Someone correct me if I'm wrong, but I believe the Native 5 is going to be the first Spyderco to have an improved lock back design with closer tolerances and a tweaking of the design, this may help with the shifting issue we are feeling?

Blerv · #8

JimP wrote:+1

All my back locks have this shifting when under pressure, it has been talk about a fair bit on these forums, all my knives have proven to be very safe and secure, albeit a little disconcerting at first.

Someone correct me if I'm wrong, but I believe the Native 5 is going to be the first Spyderco to have an improved lock back design with closer tolerances and a tweaking of the design, this may help with the shifting issue we are feeling?

I think if this sensation bothers people they should not buy lockbacks because it's an inherent design feature of the design. The amount "shift" is just like lateral "play" being a subjective on the user. Even when people say something "locks like a bank vault" there is some wiggle which to others is unacceptable.

You could open 10 new knifes and they could all have drastically different amounts of play, tension, shift, etc. Likely all would be "within spec" as they all made it past QC.

The engineering needed to eliminate this feeling is likely down to the micron making tight tolerances even tighter. On a manufactured level it's going to be difficult. As Spyderco builds them as tough and reliable tools it's not a concern. It might even make the action less fluid which would be more noticable.

Generally I buy other knives than lockbacks because I'm not a fan of this sensation and I don't need the stiffer snapping detent pressure. Everyone is different.

DeathBySnooSnoo · #9

I just tried on my Stretch and I have such a small amount that I am not sure that I would even call it flex...the blade moves a minute amount and the lock bar, shifts ever so slightly...and that is with a fair amount of pressure pulling down on the tip of the blade.

tecstrat · #10

Blerv wrote:
http://www.spyderco.com/forums/showthread.php?t=38899

It doesn't make it any weaker, just different.

This is interesting! Thx!

wsdavies · #11

Jimmy Crack Corn....

224477 · #12

Yup, lock backs /or mid locks/ do that. Unfortunately. My beloved Police 3 started to have small amount of this vertical play, I guess because the 4" blade has too much leverage.

Frapiscide · #13

tecstrat wrote:That seems like a reasonable explanation. Is it a bad thing?

No, everything has to have gaps in order to move, even if the gap is very tight, there still are gaps.

tecstrat · #14

Frapiscide wrote:No, everything has to have gaps in order to move, even if the gap is very tight, there still are gaps.

I see what you are saying but this is not the case with liner locks nor another lock-back I just tested by another manufacture.

Honestly, I know this is not going to be popular but I think this is a short coming not of the lock-back design but of the Spyderco design.

Makes me wish the Delica had a liner-lock instead (sorry lefties!).

araneae · #15

tecstrat wrote:I see what you are saying but this is not the case with liner locks nor another lock-back I just tested by another manufacture.

Honestly, I know this is not going to be popular but I think this is a short coming not of the lock-back design but of the Spyderco design.

Makes me wish the Delica had a liner-lock instead (sorry lefties!).

You really can't compare liner locks and back locks, they are apples and oranges. That said, I have seen plenty of liner locks out there with play.

The slight movement is the lock bar and blade moving in conjunction. It will not effect the safety or performance of the knife. You may consider it a shortcoming, but I would trust a Spyderco mid-lock over anybody's lock back or liner lock. If the very slight movement is part of ensuring a stronger lock, I will happily live with it.

jezabel · #16

As you might have realized by now this situation is rather common with lock backs.
My Chinook III displays some definite movement during heavy push cutting, this is not slack or sloppy in any way ( I think of it more as cushioning ) this has never impacted on it's performance. IIRC my old "Walmart' Native might have shown some give too.
FWIW though my Caly Jr shows no detectable movement nor do either of my beloved Persians and my old Mini Manix was unbelievably solid in this respect and to this day is this best fitting lock back I've encountered.

J

defenestrate · #17

While I can occasionally feel that little bit of flex while using my lockbacks (and the majority of my :spyder: knives are), it does not affect performance. If anything, upon feeling that slight flex as the blade and bar engage under load, knowing how these knives are built and work, I simply admire their capabilities and feel confident that the knife in my hand is purpose-built and more than capable of doing its job.

The Deacon · #18

It's perfectly normal. Everything in life involves trade offs and that "flex" is one of the prices you pay for the benefits a lockback provides. FWIW, some fixed blade knives with hidden tangs will do the same thing.

dalefuller · #19

Deacon and Blerv are right... it's inherent in the design of a back- or mid- lock. I've had it in the lockbacks that I've carried all the way back to the 70's when I first started carrying Bucks and Brownings.

Never affected performance, never hurt anything... just a feature of that lock style. Even with that "feature", back- and mid- locks are still my favorite locking system

Zenith · #20

As others have stated. It is part of the design. In fact. I remember reading a well know makers comments years ago that a backlock with a bit of flex in it can be better, take more strain then one without any flex.

BTW. The tolerances on a delica and endura are not as tight as on other models. The hole through the lock, handles and the pins themselves might cause the flex, but it does NOT affect the safety of the knife. You wont believe how much flex I have in my Salt 1 and it is still going strong and it is one of the older models and it has seen its share of hard cutting chores.