can a slip joint fail easily or at all under "normal" cutting?

[jbmonkey]

what i don't mean is side to side tugging with a slippie or trying to stab something or other ridiculous uses. what got me wondering on this was.....

i was in my workplace walking by some planters we have and noticed some trimming up was needed and it was on a saturday and i decided to take on the task and remove some woody weedy bushes and vines. i had my case sodbuster jr. cv with me, so it was being used. it was plenty sharp and removed stuff easily, but there were times were i had to reach in to a good bush and downward pressure cut a woody vine and use allot of pressure since controlled chunk/shaving removal couldn't be done with the space without tearing up hands on the good bush. yeah i know right tools for the job, gloves and cutters and such i failed on that, but........

i was wondering while doing it how much stress a slip joint could take before it would fail? needless to say mine didn't fail at all and handled the tasks fine. yet i am still wondering how much stress could a slip joint take before failing? my thoughts at this time is under any "normal" tasks it couldn't fail, minus a faulty pin or liner or whatever failure from the factory...but taking those instances out of the equation......a slippie is a pretty strong design isn't it? sure seems to be when being used for downward and away from yourself cutting. i am sure i am describing that all wrong, but what i mean is normal cutting that won't allow the blade to close on your hand, or to over pressure and bring the knife blade back towards a piece of your body.

that said.....even a rough rider or other value slippie should do fine on all things relative of course, hard normal cutting use. am i wrong to assume this? anyone have any feedback from personal experience that says differently than i am thinking? thanks in advance...


note: while i thought maybe the general forum would be maybe a better place for this topic, i realized those who use slippies often and have allot of experience would be a better source for firsthand information. if i thought wrong, my apologies to the moderators...i hate to create more work for ya'll. feel free to slap me upside the head for making your day harder than it should have been.

 

[Blues]

A well made slipjoint with the springs and blades properly heat treated should be a pretty hardy animal. You can see that these knives have been used hard and put away wet for many a year with few complaints by and large.

That said, one never knows when a spring might fail or a soldered joint give. Sometimes a pin need peening if some play develops...

If I intuit that a job requires harder work than I think a slipjoint was designed for (not that it won't succeed at the task), then I'll opt for a fixed blade in its stead...but I think these knives are a lot tougher and more capable than most folks would expect for the most part.

 

[jbmonkey]

understood, thank you Sir for the information.

 

[The Government]

As an interesting aside to slip-joint strength and regular cutting pressures -the thin blades and bevels of a slip joint will cut through material using less force than a thicker modern style blade. Since you are using less force to do the same job, your knife will not have to work as hard at being strong anyway.

Kind of like the difference between cutting cheese with a thin piece of string VS a meat cleaver.

 

[Blues]

You're more than welcome, jb. Hopefully some of our hard using ranch and farm hands will chime in and tell you what their experiences have been.

I can tell you this...I once used my sheepfoot bladed rigging knife to fit industrial carpet along the borders of a couple of large rooms. (Hey, I was in my twenties and didn't know any better. )

Bottom line...the knife came through the job a bit duller than when it started but none the worse for wear with no discernible wobble or play...and this was some tough material.

 

[Obsessed with Edges]

Every single person has a different idea what 'normal cutting' means, so I won't even get into that.

Otherwise, if you're lucky, you'll begin to see signs you're working the knife a little too hard. Watch for excessive (sloppy) blade play. In particular, with a sodbuster, pay close attention to the lateral (sideways) play. This pattern would be most vulnerable to lateral bending or twisting, because the bolsterless pivot isn't as strong. If it fails, it'd likely be due to the pivot pulling apart. I think most sodbuster knives use a compression rivet for the pivot pin, which might pull apart more easily if excessive force is applied laterally.

 

[jackknife]

I've never had one fail me yet, and I've leaned on a few here and there. Most well made slip joints will take more pressure than you can put on them with your bare hand.

In my sodbuster days, I used the heck out a yella Case and a yella Eye-Brand, and none of them got sloppy. I've used the screw driver blade on a Wenger SI to pry with, carefully I may add, and it's still snug. I have nothing to show in the way of scientific testing, but I don't think soddies are any less rugged than a normal bolstered knife. The two knives I've used the heaviest was a Buck 301 stockman and a yella sodbuster. Neither of them every failed or loosened up that I can tell. I leaned on both of them.

Under 'normal' use, you'll probably sharpen the blade way down before you break anything.

Carl.

 

[Modoc ED]

I've never had a slipjoint knife fail on me in all the years I've used them. Even in my younger days when I used them for throwing knives or played a game of mumbley peg, they held up just fine. Maybe got a little blade slop when used for throwing but nothing that couldn't be remedied with the light tap of a hammer or the light squeez of a set of vice jaws.

If I'm going to do a task that makes me think that the blade might/could fold back over my fingers, I'll choke up on the blade and place the pad of my thumb over the spine of the blade where it abuts the spring and I'll place the first joint of my index finger under the spine along the kick between the choil and bolster. Never been cut or had a blade fold over using that hold.

Just last week I was working on my tractor and used the pen blade of a jack knife I was carrying to trim a battery cable. When I was done, I closed the pen blade up and set the knife on the tractor tire and forgot about it as I fastened the battery cable to the battery. Long story short -- when I moved the tractor the knife rotated with the tire in a chevron groove of the tire and I ran over the knife as it came to rest in a bed of gravel. Crap!! A small stone pushed the upper handle pin back into the frame, sprung the handle up quite a bit, and scratched the heck out of the handle. Well, I put a piece of popsicle stick into the frame, pushed the handle pin back up into the handle and pused the handle back down over pin. At arms lenght it looks pretty darn good and after polishing the scratches out with some fine grit sandpaper it's hard to tell anything happened to the knife.

Yep, overall, I have to say that the slipjoint is a good, solid, tough, design that has proved itself over time.

 

[Pete1977]

slipjoints don't fail in the sense that a locking blade would. If a locking folder fails, there is nothing keeping the blade open securely. For a slipjoint to fail, the actual backspring would have to break. Otherwise there is always continual spring pressure exerted on the blade to keep it open. eg. it won't just flop closed on your fingers. I've been using a inexpensive stockman (I am a commercial lobsterman) for the last month and a couple of times when I exerted too much pressure on the spine of the blade I felt the blade start to close, but remove the pressure and the backspring takes over and keeps the knife open. You would need a significant amount of pressure on the back of the blade to overcome the strength of a backspring in a slipjoint, as in when you close the blade, or if for some reason something strikes the spine of the blade.

 

[Obsessed with Edges]

I've noticed a tendency with my soddies, for the blade to move a little bit laterally, when sharpening/stropping the blade. With the tip of my index finger near the tang of the blade, I can feel it move a bit to the side when the blade is laid on the hone/strop. Some of that play has developed largely on that activity alone. I've 'squeezed' the pivot back snug a time or two, but it always loosens up again. There may be an outward limit to how far the pivot loosens up and, in the end, it may hold together well enough under 'normal' (sensible, intelligent) use. I'd be more concerned about enough slop developing to allow slippage between tang & backspring, allowing the lockup to slip under pressure (Edited to add: this point is illustrated in my next post, below).

The bolster is, by definition, a means to "strengthen, sustain, aid, reinforce, fortify". The lack of a steel/metal 'bolster' on a knife's pivot, which otherwise gains it's lateral strength from the rivet, two thin brass liners and flexible delrin scales, might imply something a bit less 'fortified'.

 

[Obsessed with Edges]

There's an older thread in the Maint forum, regarding an old 'inexpensive' knife in need of repair, with stamped sheet metal scales/bolsters. The OP's photos, two of them seen below, are an extreme example of how a slipjoint might fail, given sufficient abuse:

(photos below are linked from this thread --->: http://www.bladeforums.com/forums/showthread.php/818189-Old-Folder-Needs-HELP!!!!-Project-Completed )

 

[puukkoman]

Hm... if you posted this in the General forum, they'd probably set you on fire and scream at you for using "one of those dangerous knives without a lock."

I've used non-locking folders like these for my whole life, and while that's not quite as long as some of the guys here (I'm around 30 y/o), I think it's long enough to have an informed opinion.

Now, keep in mind: I'm hard on my tools. I break stuff. But, I still use them properly... mostly.
To date, I've never, ever had a slipjoint "fail" on me.
There have been a few that have sustained some damage, after extended abuse. One or two have developed significant side-to-side play in the joint(s). But, that's pretty easy to fix on your own, with a little patience and some basic hand tools.
Once, after I cut off a downed oak sapling ~3" in diameter with a Swiss Army Knife (the kind without a saw blade), that particular knife became vertically sloppy (probably due to a bent pin somewhere... oak is hard stuff!! ...and I still have the hiking stick I made out of that little tree, all these years later).
However: I've never, not ever, had one of my traditional folders break due to any normal (and some abnormal) use.

These are sturdy, reliable tools... don't be fooled by their compact size and good looks!

 

[jbmonkey]

Gentlemen, lots of good information for me to ponder and absorb. thank you, Sirs for taking the time to pass it on to me. greatly appreciated.

 

[L. Richard]

In over 60 years of using (and occasionally abusing) slipjoints, I've never had one to fail under normal usage. Of course, the knives have mostly been Case, Buck, or Victorinox, which have a reputation for reliability.

 

[Voltron]

I'd be more worried it would close on you if used improperly then fail. As has been said, there are a lot of things that can go on a slippie. Springs, pins, etc. Many factors contribute to a slippie's strength/durability, but all things being equal and working properly, a slippie is tough to beat. However, stabbing movements might cause it to close on your fingers, as well as some other improper usage. Observe proper slipjoint procedure, be careful, watch your fingers, and use the heck out of it.

 

[Ken44]

Alot of good post above.

I'll just add that I've used them a good bit for the past 40+ years, and never had a problem when used properly.
I'm not to rough on knives these days, but when I was a kid we put em through pure heck. I messed up a couple, and broke the tip off a couple, but that was all my fault and would have happened with most any folder. I finally learned not to throw them, or pry, at around age 10,lol.

 

[quattromori]

I assume any folding knife will eventually fail. But I've never seen a knife come to that, not even close.
It's probably the same thing about locking...but that's another story (Puukkoman beat me with his "Hm... if you posted this in the General forum, they'd probably set you on fire and scream at you for using "one of those dangerous knives without a lock."...that's the first thing that came into my mind too)
Using your knife properly, and paying attention to what's going on as you use it, should be more than enough to prevent the knife from failing. Also, sometimes it's just wiser to choose a fixed blade for harder tasks (and I mean harder...no "general use" task would put in danger the integrity of a slipjoint).
Fausto

 

[Thomason]

Mister Bose speaks on the strength of those shadow pattern bolsterless knives.

I think they are stronger when made with micarta because there is no joint where the handle material meets the bolster. That is the weakest place on a bolstered knife. I've seen old knives that were bent at that point from abuse.You can tear any knife up because they can't be made stupid proof. This type of shadow construction will take a lot.

http://www.bladeforums.com/forums/showthread.php/468281-Bose-Knives?p=4577451#post4577451

 

[CUTS LIKE A KRIS]

Last year I couldn't decide on what slipjoint to take hinting with me. I posted a question here about what of my final 4 to use. Somebody mentioned that my GEC Executive Whittler wasn't strong enough for camp use.

So I took the challenge and brought that thin 4" knife. It worked beautifully at food prep and woodwork, carving, and any sundry tasks I asked of it. I only cut with it, but gave full faith that the knife is more than capable of handling work. Now comparing that knife to my Lanny's Clip by Lloyd, or S&M baby sunfish and I don't think that outside of abuse that there is much they cannot handle.

 

[midnight flyer]

Hopefully some of our hard using ranch and farm hands will chime in and tell you what their experiences have been.

I can tell you this...I once used my sheepfoot bladed rigging knife to fit industrial carpet along the borders of a couple of large rooms. (Hey, I was in my twenties and didn't know any better. )

Bottom line...the knife came through the job a bit duller than when it started but none the worse for wear with no discernible wobble or play...and this was some tough material.

Not a farm hand or rancher, but have been in construction for about 40 years now. Never have I had a time when I didn't have a slip joint in my pocket. I use my knives for any task at hand. They are not spared any hardship if the conditions call for it.

My slip joints have routinely open packing boxes, cut strapping, trim shingles (ONLY in emergency), cut sheetrock, sharpen my carpenter's pencils, cut up my lunch, trimmed moldings, scrape spark plug/points contacts, pry out old caulking from windows, cut carpeting and on an on. Some of these were daily tasks. Never have I had a knife fail.

In fact, I have a large CASE copperhead that I bought new in the late 70s and have used so much that the point of contact at the heel of the blade where it contacts the spring when open is starting to deform (mushroom). THAT is some constant/hard use that took a period of years, or as I like to think, some "good lovin". That knife was the only work knife I had for years and it has gone well and above any reasonable expectations for a knife with years of hard service. Still has pretty strong snap on the main blade, and great snap on the less used pen. Amazingly, it has never worked itself loose anywhere!

Think of all decades that have passed by where the slipjoint knife was a tool, a necessary implement in a boy or man's pocket. Traditional slipjoints seem to be pretty much collector materials these days, but the patterns are based on time tested designs that have proven themselves in all situations for years. There are plenty of good work type knives out there to suit just about any trade or task.

I would buy a good quality slipjoint ( you won't have to spend $80- $100 ) for work and carry it with all confidence that it would perform the above mentioned tasks as needed. People have for many decades.

I never leave my house without a slipjoint in my pocket.

As always, just my 0.02.