How do lockbacks wear?

sph3ric pyramid

sph3ric pyramid

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Jul 24, 2002
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I posted this on another forum, but though I'd bring it up again and get a few more opinions.

How do lockbacks wear over time? What parts wear against each other, to what extent, and how is lock stability affected? I've never used a lockback hard (tho, do have a Native on the way :D ), so I'm curious as to how they hold up over time as compared to other lock formats. Also, when the lock breaks, I'm guessing that the locking bar just snaps?
 
I have never had a lockback break or wear out and I have had my Buck 110 for almost forty years. Nothing has even gotten loose on this knife.
 
No clue.
All my Spyderco has no wear shown, no matter how I use it, flick it, play with it.
The locking slot does collect lint, so you do want to clean it out at least one in a while, that could affect the lock performance.
 
My experience is the same. I've been using lockbacks since early 70's with no problem at all. Buck and Spyderco mostly.
Bob
 
I've got a Buck 112 from the mid 70's and the only thing done to it was having the tang ground by Buck so it wouldnt gravity open.
 
I have a Puma lockback that is about 20 years old. The tab that fits into the notch has worn down some. Now it takes considerably less of a push to unlock the blade. The lock could be disengaged by squeezing hard. This was solved by dremeling in a Boye dent. I know of someone else who had the same trouble with a Puma. Probably the lock bar is softer than the blade, thus the wear.
 
The back of the tang as well as a metal bar pushing against a spring (the lock lever)come in contact. Lockbacks can go through with minimal wear if you let the lever go slowly when you're opening it so the metal on metal contact isn't too great. The wear on these isn't bad compared to other mechanisms such as liners IMHO.
 
Look at the motion in a lockback.

The locking bar moves in an arc. The lock is made up of a square tab on the lock bar and a square notch in the blade tang.

Arcing two square pieces together makes corners rub. The corners wear down as do the edges they rub on. The increased gaps that result lead to looser and less reliable lockup and allow more lint into the system (minutely more).

That's how they wear. How much and how fast is a game of materials, usage frequency, and usage stress, same as any other lock.

I've had some get sloppy. I've had the leaf springs on the lock bar wear out, break, or shift. I've never had a grip failure, but I haven't used lockbacks nearly as heavily as other locks so my sample is far from conclusive. Overall, I still think the lock back is a good design, just not as user friendly as some others popular right now.

Phil
 
I have quite a few lockbacks and they have never failed in any way, The one I used and abused most was a Buck 112 for about 20 years, it got scratches all over and some marks on the bolsters (from using as a hammer a few times), the wood handles also got worn a bit, but no functional problems and the lock always held fine.
 
On my Spydercos the round tang becomes polished.
Using in house custome made machines exerting thousands of PSI they do lots of failure testing on their knives, at least 2 out of every 500 to 600 piece production run even.
When finaly the knife does fail it is often the pins and other fasteners that precipitate the failure! You cannot break their Heavy Duty or MBC locks by hand.
 
I agree with phatch, that the squared-ends where the spring and notch meet begin to round. Though I'll point out that on a good lockback that seems to take a very long time. Still, as that happens, what it means is that the lockup becomes a little less secure, little by little.
 
One more question on this. So am I right in saying that as the locking tab wears, it becomes easier to disengage via the unlocking tab, but if the locking notch is sufficiently deep no blade-play will result? Wouldn't it take a significant amount of wear for a lock-back to become unstable in any way (unless the lock geometry and materials are crap)?
 
Any metal to metal will wear out both parts where they touch eventually.

I've seen Buck 110's on cops belts [ not recently ] that had been abused as prybars, ice picks, cutting metal with the edge, you name it, these 110's aaw it over 20 years.

The lock was worn out on most of them, the edge was a butter knife, the tips were all broken off, they had surface rust in spots, etc. etc.

There was lateral play galore as well on all of them from wear.

These were not carried for 20+ years, they were used continuously and roughly in all kinds of weather with nary a thought about it.

I do believe a few of my lockbacks will wear out, they are being used daily and if I continue to carry them and use them this way, I expect by taking care of them, unlike the lockbacks above, I should get 20+ years out of say, a Chinook, whose steels are better, whose heat treat is better, whose polerances are better, etc.

Perhaps it is the MPC, but more likely the ER Fulcrim 11D I now carry that will wear out and become unreliable. Thats fine with me as it can be fixed or replaced with another or another knife all together at that time. Of course I'll be happy to replace it when it wears out. I'll be in my early 70's:rolleyes:

Lockbacks have proven to be hard use easily maintained [ or more likely not maintained ] folders that have a good strong locking system not prone to failure easily.

If lockbacks were prone to be fragile, the buck 110's would never have become the officers knife of choice during the 60-70' era.

Lockbacks have come a long way since the 110 was made. I have no fear of any of mine wearing out before I do at this point.

Brownie
 
The deeper the lock mechanism is cut, the more problems there are. Arcing two deep squares together accentuates all the wear points They contact more acutely and for a longer time in the motion. The deeper the tang notch is, the wider the notch has to be to allow the pieces to arc together. And the more gap you have to design into the system in the first place; lock loseness.

Additionally, the cutout for the lock release has to be correspondingly deep to allow for the motion to unlock the blade. So you'd probably have to use a weaker spring to make it useable. And the handle changes could be unpleasant in use or even strength in an FRN design.

And you might think that you could build an arced notch and tab system. To some degree. A night or two ago, I was thinking I could patent that idea, perhaps, sort of like the patent BM has on the arced lock ramp on liner locks. But I decided it wasn't very effective.

If you made the notch and tabs in the same arc described by the lock bar in motion, then there is little to no locking friction, just spring friction. That arc is small so you don't have much room to play with arcing designs, probably not enough to account for the variances in production.

The current lockbacks are already good in a quality knife.

Phil
 
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