Impact of Inertial Opening on Lock Life

Discuss Spyderco's products and history.
User avatar
timlara
Member
Posts: 1383
Joined: Fri Sep 24, 2004 10:33 am
Location: Lakewood, CO

Impact of Inertial Opening on Lock Life

Postby timlara » Thu Mar 11, 2004 1:00 am

This question is sort of two-fold:



I prefer the speed and motor simplicity of inertial openings (as demonstrated in Michael Janich's videos), but I am curious to know what people's opinions are as to whether this technique might damage a knife's locking mechanism over time. (I'm talking about any quality locking system such as those found on Spyderco knives, be it lockback, compression, ball-bearing, what have you...)



Secondly, I seem to remember reading somewhere that some manufacturers consider this type of opening to be abuse that could void your warranty. What is Spyderco's stance on this, especially since they endorse Mr. Janich's philosophies?



Thanks.

Joe Talmadge
Member
Posts: 1077
Joined: Fri Sep 24, 2004 10:33 am

Postby Joe Talmadge » Thu Mar 11, 2004 10:55 am

I don't think there's any doubt that intertial openings increase the wear rate to some extent or other. However, I also know that a well-made knife can take years of intertial openings without showing any signs of real wear or damage. So if you're talking about investment knives, I'd say don't do intertial openings with them. But in the context of MBC, if intertial openings are what you favor, then do them. If your knife can't take it, get a better knife. And if the knife starts to show some wear in a few years -- hey, let's face it, we're knife knuts, we'll be buying a new knife in a few years anyway.

One of the advantages of well-made trainers is that you can do all your practicing on the trainer. If the trainer is manufactured exactly the same way as the working knife, then you'll get some idea on the trainer as to how the working knife holds up to inertial openings. And you won't cry in a few years if your trainer starts showing some strain -- it's a trainer, it's supposed to get beaten to pieces.

I think the really interesting question is: given the stress you'll be under, aren't you worried about accidently throwing your knife across the room instead of opening it? I go back and forth on inertial openings vs. slower-but-controlled openings, usually favoring the latter.

Joe

The Saint
Member
Posts: 117
Joined: Fri Sep 24, 2004 10:33 am
Location: Kitchener Canada

Postby The Saint » Thu Mar 11, 2004 10:57 am

Well, I've opened my CRKT Wasp thousands of times over the 3 years I've owned it, most of the time via the "wrist-flick" method, and it has yet to exhibit any blade play whatsoever, and it has never failed to lock up perfectly.

Now, speaking generally, CRKT products are of lower quality than Spyderco, so I imagine they'd be safe from just about anything you could throw at it.

The Saint
Member
Posts: 117
Joined: Fri Sep 24, 2004 10:33 am
Location: Kitchener Canada

Postby The Saint » Thu Mar 11, 2004 10:58 am

Well, I've opened my CRKT Wasp thousands of times over the 3 years I've owned it, most of the time via the "wrist-flick" method, and it has yet to exhibit any blade play whatsoever, and it has never failed to lock up perfectly.

Now, speaking generally, CRKT products are of lower quality than Spyderco, so I imagine they'd be safe from just about anything you could throw at it.

User avatar
timlara
Member
Posts: 1383
Joined: Fri Sep 24, 2004 10:33 am
Location: Lakewood, CO

Postby timlara » Thu Mar 11, 2004 11:39 am

All good points so far. To be sure, accidentally flicking your knife across the room in a bad situation would cost you a lot more than the 1/2 second you'd lose by opening it in a safer manner. And I won't be practicing this technique with my collectors edition knives. It sure is quick and fun, though!

I only recently became interested in Martial Blade Craft, so right now, I'm just trying to learn whatever I can. I have yet to pick up a trainer, but it is definitely next on my list. Thanks for the replies!

Michael Janich
Member
Posts: 1682
Joined: Fri Sep 24, 2004 10:33 am
Location: Longmont, CO USA
Contact:

Postby Michael Janich » Thu Mar 11, 2004 2:26 pm

Dear timlara:

Thanks for the question and thanks also to all those who responded and shared their thoughts.

In my experience, intertial openings tend to cause the greatest wear on lockback knives, since the impact of the blade on the front of the locking bar, over time, tends to peen the face of the bar and change the relationship of the mating parts. Ultimately, this will result in lock failure. I've intertial opened several different high-quality brands of knives "to death" -- meaning that the locks ultimately failed. At that point, I retired the knives (keeping them around to demonstrate the phenomenon in classes, of course) and replaced them with new ones.

Well-made liner locks that compensate properly for wear and start their lives with a good locking engagament tend to be more forgiving and last longer. My original MOD Tempest endured tens of thousands of inertial openings without a problem. Because of its separate locking bar design, when the lock bar moved too far over or I noticed any slight blade play, I readjusted the bar and was back in action within a few minutes. Integral or split liner locks, once worn, cannot be fixed in this way.

If you choose a liner lock, make sure it has a hardened stop pin (if it is a stop pin design). The impact of inertial openings will flatten a soft stop pin and change the lockup. One well-known brand of knives is notorious for this. After I got tired of rotating the pin to compensate for it, I replaced the pin with a piece of hardened drill rod. I then switched to a better knife.

As far as Spyderco's opinion on inertial openings goes, I'm pretty sure that they still consider them to be a form of abuse. Sal has told me straight up that he doesn't particularly like the fact that I teach them, but I consider them an indespensible part of my personal approach to MBC and a viable option for everyone else. As such, I will continue to teach them. As for Spyderco's endorsement of the MBC program, what Sal and Spyderco like best is MBC's commitment to responsible, ethical, and legally defensible self-defense with edged weapons. That's really what they support and endorse. When it comes to inertial openings, we agree to disagree.

The bottom line is that inertial openings can be an excellent method of getting a knife into action quickly. If you choose that method and can make it work under stress, understand that it will cause your knife to wear more quickly. Check your equipment often, maintain it well, and replace it when necessary. I'm sure you'll still find that Spyderco knives and other high-quality brands will still give you great, long service for your money.

Stay safe,


mike j

User avatar
timlara
Member
Posts: 1383
Joined: Fri Sep 24, 2004 10:33 am
Location: Lakewood, CO

Postby timlara » Thu Mar 11, 2004 3:22 pm

Great info, Mike. Thanks!

BRAM
Member
Posts: 478
Joined: Fri Sep 24, 2004 10:33 am

Postby BRAM » Wed Apr 07, 2004 3:33 pm

Well the compression lock was designed to absorb the impact of opening..Kinetic opening is as rough as inertia opening..if not more..
I've opened my DRONE tens of thousands of times kinetically and there's no play at all..and I ABUSE my tools to demo how strong they are..

Yes I know its a bit off topic..ie is ineertia opening abuse...
BUt there are locks designed to take abuse..
Liners compensate as well..
(And if Mike says it works,,it works!)

Try a compression lock...

be safe
Bram

brownie0486
Member
Posts: 46
Joined: Fri Sep 24, 2004 10:33 am

Postby brownie0486 » Wed Apr 07, 2004 3:52 pm

I destroyed a custom titanium Elishewitz linerlock over 4 years popping the knife literally hundreds of times a day. It was the off side folder as well [ left handed ].

Sent it back to Alan who repaired the damage and sent it back for shipping costs only. It hasn't been carried since, that was 6 years ago I got it back from Alan.

He found that the stop pin had been destroyed which allowed the knife blade to go beyond the distance it normally would in the locked position. On a slashing exercise, the pressure applied released the lock, the blade collapsed onto the fingers, but alas I beat old Murphy once again as I was wearing leather frisk gloves at the time.

Brownie

User avatar
Mike Sastre
Member
Posts: 419
Joined: Fri Sep 24, 2004 10:33 am
Location: Hamilton, Ohio USA
Contact:

Postby Mike Sastre » Thu Apr 08, 2004 4:37 am

Not all inertia openings need to be done with balistic force on the stop pin. Once a little sensitivity is gained through practice, some of the openings can happen with the blade just 'kissing" the stop pin. One of the best for this is one that MJ explains in "Street Steel", where the pivot pin remains in place, and the knife handle is rotated underneath and towards the body's centerline. Can be a very controled and gentle move, as well as quick and in close proximity.

Mike

dhpd9807
Member
Posts: 37
Joined: Fri Sep 24, 2004 10:33 am
Location: denver

Postby dhpd9807 » Sun Apr 18, 2004 1:14 pm

I have beat my tempest into the ground with the inertial opening, it's the knife I learned on. over the last two years I'll bet I've done it 10,000 times. The knife still locks up just fine, if anything it locks better most of the time. Only problem is the blade now has a bit of play when open and the torx screw will not stay tight. I have tried to remove it and get loctite in there but it will not come out, result is I have to tighten it once or twice a week. I figure I'll have to send it back to MOD to get it fixed up. Any other ideas anyone?

dhpd9807
Member
Posts: 37
Joined: Fri Sep 24, 2004 10:33 am
Location: denver

Postby dhpd9807 » Sun Apr 18, 2004 1:14 pm

I have beat my tempest into the ground with the inertial opening, it's the knife I learned on. over the last two years I'll bet I've done it 10,000 times. The knife still locks up just fine, if anything it locks better most of the time. Only problem is the blade now has a bit of play when open and the torx screw will not stay tight. I have tried to remove it and get loctite in there but it will not come out, result is I have to tighten it once or twice a week. I figure I'll have to send it back to MOD to get it fixed up. Any other ideas anyone?

Michael Janich
Member
Posts: 1682
Joined: Fri Sep 24, 2004 10:33 am
Location: Longmont, CO USA
Contact:

Postby Michael Janich » Mon Apr 19, 2004 6:27 am

Dear dhpd9807:

Thanks for the post. I'm glad your Tempest has served you well.

Before you send the knife back to MOD, try covering the off side of the pivot pin with a piece of duct tape. Press it down tight to keep the pin from spinning. If necessary, tape that entire side of the knife and lay it flat on a wide, fine mill file (the teeth grab through the tape and further secure the pin in place). With everything set, back the screw side of the pin out with the appropriate wrench and Loctite away. For best results, clean the pivot pin screw and the inerior of the female side of the pin with alcohol and a cotton swab before you Loctite to remove any oil that might keep it from adhering.

Good luck!

Stay safe,



mike j

zeus
Member
Posts: 439
Joined: Fri Sep 24, 2004 10:33 am
Location: Ventura County, California

Postby zeus » Tue Apr 20, 2004 1:04 pm

Open up a ball-lock Dodo and see the blade contacts a solid one piece of steel in both the open and closed position. No stop pins anywhere... about the only thing that would wear is the hollow pivot post.

Qship
Member
Posts: 213
Joined: Fri Sep 24, 2004 10:33 am

Postby Qship » Wed Apr 21, 2004 11:21 am

>Only problem is the blade now has a bit of play when open and the torx screw will not stay tight.
__

Tacky plastic sheeting, as a substitute for tape, works for me. I got some medical sheeting, can't remember the brand, intended to cover burns on skin, which works fine.

It also helps to clean the reverse head of the pivot pin with solvent, because the head tends to get lubricant on it when you lubricate your knife. That will inhibit the head from sticking to the plastic sheet or tape.

Be advised that Locktite comes in various strength, and at least one is permanent. I suggest the weakest formulation, because if it comes loose, you can always try a more powerful formulation.

Qship

brownie0486
Member
Posts: 46
Joined: Fri Sep 24, 2004 10:33 am

Postby brownie0486 » Wed Apr 21, 2004 12:03 pm

Blue loctite, secures em until you back it out on purpose.

All the pivots and screws get blue loctite when new and have never been a problem afterwards.

Do not get the red/burned orange loctite, you will not get the parts to seperate without much effort and probably breaking something [ like knuckles ].

Brownie

Qship
Member
Posts: 213
Joined: Fri Sep 24, 2004 10:33 am

Postby Qship » Wed Apr 21, 2004 4:57 pm

There are other brands of thread locking compound besides Loctite. Unfortunately, their color codes do not always represent the same thing as Loctite's. So, reading the instructions is good.

Qship

Tonie
Member
Posts: 8
Joined: Fri Sep 24, 2004 10:33 am

Postby Tonie » Mon May 10, 2004 10:31 pm

In my experience I think the lifespan of the knife in relation to inertial opening is better considered in terms of the blade loosening and developing play than the number of years. I have three Enduras, two of which have gone through years of inertial openings and are as solid as the day I bought them.

The third one however has developed about a thirtysecond of an inch of vertical play. I can only assume that something in the quality of the metal has allowed it to deform ever so slightly from the impact. It's enough of a rattle that it can throw me off when I practice with it so I don't carry it any more other than as a backup to my primary folder.


Return to “Spyderco General Discussion”

Who is online

Users browsing this forum: 5-by-5, Albatross, attila, cabfrank, Google [Bot], kurt_r, Lumpy, Mr.B., Oloung1, pushcut, Ratamaque, rcwill98, The Meat man, Theldraskien and 37 guests