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

[Clang!]

Pretty near impossible under normal cutting for a better-built slipjoint to break. I've had the cheapie chinese knockoffs fold back, but I've abused my SAK with worse then what you did and it hasn't folded back.

 

[Obsessed with Edges]

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

No argument there, IF they were all built like the knives he speaks of (customs, and Tony Bose customs at that).

Makes all the difference in the world, when those bolsterless shadow patterns are made with stainless liners (or Ti) and fabric/linen micarta slabs (much, MUCH stronger and more rigid than Delrin), with pivots that are more than likely screwed/pinned together with oversized stainless fasteners. HUGE difference between that and the average, run-of-the-mill, Delrin & brass, riveted sodbuster.

In fact, Mr. Bose alludes to that in post #136 of the same thread:

The old shadow patterns had a pivot pin going though the handle with a head spun on it or hammered down. They were weak and always developed play in the blade. There was also a birdseye which had a thin nickle silver washer the pin went through which was better, but still not good.

BoseKnives shadow pattern has a 100 thousands thick stainless washer with a tapered hole for the pin that can be really locked down. This washer is counter bored into the micarta and then the pin peened over to mesh where you can't see the pin in the washer resulting in a rock solid pivot. If you break this loose you are doing something you shouldn't be doing with a pocket knife

 

[Bigfattyt]

Great thread.

One quick question?

To tighten side to side play in a slip joint can you just tap the pins in the bolster? Seems like it might just be a cross pin, peened into place, and smoothed over?

I have an old buck lock back that I did this to as a child. The blade developed side to side play after years of use, and I took two hammers laid the knife on the face, and gave some light taps to the opposite side. Tightened the blade play right up, and it is still tight today.

Lets say, for example a bolstered GEC Pioneer etc?

 

[Big Barn]

+1 to everything above. Carried a slippy for over 45 yrs now & NEVER had one fail. Worked on a farm (carried a Russel Barlow) every summer until I was 15 - which is why I work in an office environment now. Used & abused those barlows but never any significant failure.

 

[artmichalek]

The only way I can think of for a slipjoint to "fail", in the catastrophic sense, under proper use (loaded perpendicularly to the edge) is if there's already a crack in the blade. Then it will snap, but the sharp part will probably stay in what you're cutting. In-plane, even a cheap knife is stronger than your hand. If you load the knife sideways, the pivot pin will fail slowly because it's soft.

 

[richstag]

In-plane, even a cheap knife is stronger than your hand.

Idk, maybe my hands got strong from use at work, but I broke an 18" forged pipe wrench in half with my hands and no cheater pipe over the handle or anything ( I am guessing it had a stress point from use over time). I would never want to think I could not break a knife by hand, because I don't feel that is true. I almost think it is dangerous to suggest it actually.

I would go more with the thought that if you are exerting enough force that you feel like you could really hurt yourself if something snaps then maybe you should not be using a tiny folding knife.

I don't mean to be offensive with my comment. Just sharing my thoughts.

 

[puukkoman]

Great thread.

One quick question?

To tighten side to side play in a slip joint can you just tap the pins in the bolster? Seems like it might just be a cross pin, peened into place, and smoothed over?

I have an old buck lock back that I did this to as a child. The blade developed side to side play after years of use, and I took two hammers laid the knife on the face, and gave some light taps to the opposite side. Tightened the blade play right up, and it is still tight today.

Lets say, for example a bolstered GEC Pioneer etc?

Exactly.
Try this: Rub the bolster quickly on your flannel or cotton shirt, then breathe onto it as if you were trying to fog up a window. Now, look at it, and you should be able to see exactly where the pin is.
Protip: a gentle squeeze in the jaws of a vise is a way better method; much more controllable, so you don't over-tighten. With multi-bladed joints, it gets to be a more delicate operation, but the same concept still applies.

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.

Couldn't agree more. Get a Buck 301, and you'll spend less than $50 for a solid workhorse that will last you for as many years as dollars you spend.

 

[WA Martin]

I worked at a carpet store while I was in high school and one of my usual tasks was to trim up remnants, back roll them, and tie them with twine. I think I was using a Valor stockman at the time and after a few months would sometimes do like post #11, photo #2.

I just thought I wore out the knife. Still have it in a box somewhere. Never thought I might have been "abusing it".
I should probably point out that it only does this under pressure. As soon as I let off the pressure the blade snaps back into alignment/normal positioning.

 

[Obsessed with Edges]

I worked at a carpet store while I was in high school and one of my usual tasks was to trim up remnants, back roll them, and tie them with twine. I think I was using a Valor stockman at the time and after a few months would sometimes do like post #11, photo #2.

I just thought I wore out the knife. Still have it in a box somewhere. Never thought I might have been "abusing it".
I should probably point out that it only does this under pressure. As soon as I let off the pressure the blade snaps back into alignment/normal positioning.

That particular knife (pictured earlier) is extra vulnerable, due to the lack of any real bolster. The bolster/scale is just a single, stamped piece of sheet metal, purely cosmetic, held on by metal tabs bent around the ends of the liners. The pivot pin is anchored & peened only to the very thin liners, and nothing else. Very easy to pull it apart. So, for that knife, the abuse 'threshold' is a lot lower than for a normally-bolstered knife, for which cutting up some carpet would be 'just another day at the office'.

 

[knarfeng]

I've only had one slipjoint spring fail. That was one of the early Buck 700 series knives which my mother gave me for a birthday gift sometime in the early 80's when that series first came out. It is known that many of the first 700 series knives had faulty springs. The issue was quickly addressed by Buck and all their other knives are solid. I still have the silly thing (because it was a gift from my mother) as well as the replacement I bought a bit later.

 

[Gobbo_the_civet]

A friend's colleague batoned with a slippy, tapped right on top of where knife and spring meet and surprise, surprise, it failed. But as long as you just use the force of your hands to drive the blade and you keep it sharp, no problem.