Displaying Slipjoints with open blades

TAH

TAH

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Jul 3, 2001
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A friend of mine has been collecting slipjoints from Case, Schrade, Camillus, Buck, etc. since the 1970s. All different patterns including many that have blades that share the same backspring. He displays them with all blades opened (some probably have half stops, but most of the blades are not at a 90 degree angle). He said in all his years of collecting, he has never had one problem with any of the backsprings failing or getting weaker. He said some of his knives have had their blades opened for decades and will still operate with no problems. He specifically pulled out a boxed Schrade Old Timer Stockman Limited Edition that had its blades opened for years and he was correct, the blades opened and closed like new.

I'm more into fixed blades, but I always thought it wasn't a good idea to display slipjoints with opened blades. Thoughts?
 
When fully closed or fully opened, the backspring is at rest. What could stress a spring is leaving a blade 1/3 or 2/3 open, so that the spring is under its fullest load. You really don't want to have two blades sharing a backspring partially open at the same time.
 
Thanks. I should have stated, his are not opened all the way. Basically, something like...

1488251073_51_179_2.jpg
 
In your picture you can see how the spey and sheepfoot blades, both open at the same time, stress the shared backspring on both ends. I would open the spey all the way, so that only one end of the spring is under load.
 
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If the springs are properly heat-treated & tempered, it should never be an issue. It's really the only thing a spring is ever designed to do, which is to maintain it's shape, strength and temper over a lifetime of use. If a spring weakens over time due to it's position or due to use, that's a sign the tempering wasn't very good for it in the first place. Springs that fail usually do so as the result of some manufacturing defect.

I could see that a poor design of the knife's build itself could also exert excessive stresses on the springs, within what should be their 'normal' range of movement. I've no doubt there are some poorly-built ones out there. If so, that's another QC issue, and not so much about how the knife is operated or used. A smart design & build would allow some tolerance for the spring to easily resist damage even at it's most-stressed position in the knife's operation.

Regarding Schrade (U.S.A.) specifically, they seemed to have mastered some beautiful spring tempering of their blades in particular. If they knew how to do those right, I'd bet they did their backsprings right too.

The only springs I've ever seen that were weak, were otherwise due to excessive wear (erosion) at the spring ends, where they rub against the tang of the blade, creating excessive play in the blade's operation. I've also seen some poorly-made, brand new knives that also had too much play (vertically), creating weak closing snap and due to poor fit between the spring end and the blade tang. I've yet to see a spring weakened simply by how it's been flexed over time, and I have dozens and dozens of traditional slipjoint knives.

I bought a Case 5-blade Sowbelly some years ago, secondhand, that had been stored by a previous owner in a display tin for quite some time prior to my receiving it, with all blades opened, some of them partially. When I went to extract it from the tin's interior, a 1/3rd-open blade snapped like an alligator on two of my fingertips and sliced 1/4" diameter flaps of skin from each, right in front of the fingernails. Nothing wrong with the snap on that spring, which had partially-open blades displayed at both of it's ends. When they're done right, there's no mistaking it.
 
I had a 77 Queen trapper, that came in a presentation box with a cutout for the knife to have it's blade open 1/4 way. After 30+ years sitting like that with the blade opened, when I took it out of the box, the blade was extremely weak. It still snapped shut, but just barely.
 
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I’ve heard of it going both ways; of springs snapping when both blades were opened simultaneously, and, like your friend’s, of being left open for decades without incident. Personally speaking, I’ve tried leaving nail breakers open to try to soften them without much success.
I suppose a lot has to do with the heat treat/temper on the springs - hard enough to maintain shape, yet soft enough to remain pliable. The ones that are too hard will snap. The ones that are too soft will loosen.
ETA: I see OwE beat me to it while I was typing.
 
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Very good advice by Jeff! Nobody really knows how much long term, full load tension that one back spring can take.
Better to be safe than sorry. Trad folders were not designed to handle long term tension force from both ends, let alone one end.
 
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All springs are not created equal. Some, maybe even most, will endure partial stress forever.
But a few will weaken, and some will break.

Ha ha - I'm a slow typist!
 
Obsessed with Edges said:
If the springs are properly heat-treated & tempered, it should never be an issue. It's really the only thing a spring is ever designed to do, which is to maintain it's shape, strength and temper over a lifetime of use. If a spring weakens over time due to it's position or due to use, that's a sign the tempering wasn't very good for it in the first place. Springs that fail usually do so as the result of some manufacturing defect.
Click to expand...

This is probably my friend's position as well. He has 200-250 slipjoints and that doesn't include the ones that were sold or traded. He definitely knows his stuff and has years for experience, so I would have felt uncomfortable challenging him.

Thanks for all the replies. I was more curious than anything.
 
Obsessed with Edges said:
Regarding Schrade (U.S.A.) specifically, they seemed to have mastered some beautiful spring tempering of their blades in particular. If they knew how to do those right, I'd bet they did their backsprings right too.
Click to expand...

Schrade did a lot of things right, which is why they are the best:thumbsup:
 
waynorth said:
All springs are not created equal.
Click to expand...

I'm curious again. Do vintage Camillus contract Buck knives (like the one in the photo above) have a good backspring reputation? I'd like to know, because I have one just like it.
 
Backsprings can break, even on a well made custom. Carried / used this one for around 10 years before it broke from normal opening and closing. Considering it is D2 and looking at the rust, could have been a defect in the metal that finally rusted enough to snap except it did the same thing twice. Snappy but no nail breaker. Have three other traditional slipjoints by the same maker, all in D2, without issue. Why chance it?

brokenslipjoint.jpg
 
My position is that left open they can weaken. I've done it myself, on purpose, to ease a nail breaker and it works. Now given the range of heat treatment present in production folders, some will weaken a lot, some a little, and some not at all, but . . .
it is so easy to not leave both blades open on the same spring at the same time, so why do it? If only one spring breaks out of the 250, won't you still feel badly? I say, "Better safe than sorry!"
 
I am of the "only open one end at a time" school of thought myself, never having seen much reason to open more than one at a time in normal use. All of these responses offer very sound advice, but its probably nothing to obsess about. As my old gunsmith buddy used to say "old springs will work, until they don't". Everyone tries to avoid it, but there is really no way to tell the hour which spring failure will come in any particular knife.
 
I don't generally leave my slipjoint knives open with the spring under load. If there's even a slight a chance it might result in "the ping of doom", I'm going to avoid it.
 
All springs have an elastic limit. If the limit is exceded, the spring will snap or stretch. When you partially open two blades sharing a backspring, you’re getting closer to the elastic limit than is necessary. Test away (at your own risk).
 
The message is clear.
Yes, if the springs are well tempered and the knife well made, you should not have any problems with it.

BUT!
The way you find out is breaking a spring and ruining the knife for the most part.

There really isn't any middle ground, it is Binary. It will fail, or it won't.
To each his own as to whether it is worth the risk to display blades at full spring tension or more risky - have both ends of a spring at full tension with opposing blades displayed. Nothing wrong with a "Live Fast, Die Hard, Leave Clean Underwear" lifestyle.

It's your knife, do what you want with it. Just don't bitch about "bad heat treating" or crappy manufacturing if it goes against you.
 
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