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Extended implements: strain on the back spring?

00 Offline Simon_Templar

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Extended implements: strain on the back spring?
on: January 25, 2022, 08:53:10 AM
Fellow knights,

I wonder if any of you know whether leaving an implement extended continuously wears out the back spring? I would think not as Vic themselves are selling SAKs with extended implements (=large blades in its Damast collection), but I am not certain and would be curious to know. Thanks for any input!

Cheers,

Simon


cy Offline dks

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Re: Extended implements: strain on the back spring?
Reply #1 on: January 25, 2022, 09:05:42 AM
I would not expect that to wear it out.

However, leaving it half open, with maximum strain on the spring, has been seen to weaken the spring and is used as a way to weaken springs in folding knives, if they are too strong.
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pt Offline pfrsantos

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Re: Extended implements: strain on the back spring?
Reply #2 on: January 25, 2022, 12:07:51 PM
I would not expect that to wear it out.

However, leaving it half open, with maximum strain on the spring, has been seen to weaken the spring and is used as a way to weaken springs in folding knives, if they are too strong.

+1

The springs are built to keep the tools open/closed with minimum strain. That's why they snap into place, when opening or closing. The half open/closed position is the problematic one, because the spring is trying to send the tool either into open or closed position.
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us Offline Adam5

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Re: Extended implements: strain on the back spring?
Reply #3 on: January 25, 2022, 01:52:01 PM
Creep

An extended implement is not placing the spring under a lot of strain and should not cause much creeping. As dks and pfrsantos have stated, an implement in the half-open position is placing the spring under maximum strain and would cause more creeping.


00 Offline Simon_Templar

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Re: Extended implements: strain on the back spring?
Reply #4 on: January 25, 2022, 02:31:58 PM
Thanks knights, much appreciated :hatsoff: So you reckon the only thing that would wear out the back spring is half extended tools? That would mean that in theory, you could store a SAK with all implements extended and it wouldn't be any worse for wear. Weird.


gb Offline Tasky

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Re: Extended implements: strain on the back spring?
Reply #5 on: January 25, 2022, 03:18:47 PM
Thanks knights, much appreciated :hatsoff: So you reckon the only thing that would wear out the back spring is half extended tools? That would mean that in theory, you could store a SAK with all implements extended and it wouldn't be any worse for wear. Weird.
It also means all those models in the shop displays with the tools splayed are likely quite smurfed up, so you may be able to argue a discount on an ex-display model!


us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #6 on: January 25, 2022, 04:46:12 PM
The actual answer depends on many factors everybody above is ignoring.

Tang styles and era of production have lots to do with how bad it is to leave the tool open or whatever various positions in between.

At the extreme, some are even better off stored open. 111mm slide locks leave the backspring in a lower stored energy state than closed.

Some tangs like inline Phillips and 90° caplifters are about the same in the 90° positions. Highest spring stress is closer to the 45° and 135° positions.

I would never store a knife from about 1970 and earlier with tools in part open states. Also wouldn’t recommend it for ‘80s. ‘50s and earlier it’s a total sin and doing this is almost asking for a spring to break. But I wouldn’t hesitate to do so for knives from the ‘90s and later. Factors like surface polishing and tang and spring seat designs and interactions all play a part in this issue or lack thereof over time.

Essentially, new knives have lots of details that keep the backspring out of any real danger of creep, bending or fracture. They operate well within the lower elastic range of the steel they use. Please trust that Victorinox actually made significant improvements over the years, and that we all benefit from these developments.

So enjoy and display your modern knives as you please. But be nice to your older friends.
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00 Offline Simon_Templar

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Re: Extended implements: strain on the back spring?
Reply #7 on: January 25, 2022, 04:58:02 PM
The actual answer depends on many factors everybody above is ignoring.

Tang styles and era of production have lots to do with how bad it is to leave the tool open or whatever various positions in between.

At the extreme, some are even better off stored open. 111mm slide locks leave the backspring in a lower stored energy state than closed.

Some tangs like inline Phillips and 90° caplifters are about the same in the 90° positions. Highest spring stress is closer to the 45° and 135° positions.

I would never store a knife from about 1970 and earlier with tools in part open states. Also wouldn’t recommend it for ‘80s. ‘50s and earlier it’s a total sin and doing this is almost asking for a spring to break. But I wouldn’t hesitate to do so for knives from the ‘90s and later. Factors like surface polishing and tang and spring seat designs and interactions all play a part in this issue or lack thereof over time.

Essentially, new knives have lots of details that keep the backspring out of any real danger of creep, bending or fracture. They operate well within the lower elastic range of the steel they use. Please trust that Victorinox actually made significant improvements over the years, and that we all benefit from these developments.

So enjoy and display your modern knives as you please. But be nice to your older friends.

Many thanks for your knowledgeable answer, Kamakiri :hatsoff: I am sure I am not the only one to appreciate your explanation very much :cheers:


nl Offline Reinier

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Re: Extended implements: strain on the back spring?
Reply #8 on: January 25, 2022, 05:04:20 PM
This is a nice opportunity to talk about the "Huntsman with chisel" display knives with the altered tools that allow for them to stay open in certain positions.
You should seriously visit vicfan.com. All the hoopy froods are doing it.


us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #9 on: January 25, 2022, 05:24:04 PM
Many thanks for your knowledgeable answer, Kamakiri :hatsoff: I am sure I am not the only one to appreciate your explanation very much :cheers:

 :cheers:

Thanks for starting threads that encourage knowledge, experience and discussion!

I did think of one thing I should add. There are ways that I would not do with the two outer/3-tool layers. Like 135° caplifter, 90° can opener, 45° awl all at the same time. That would put this layer at it’s maximum bending. And while I think it’s not that bad, 90° or open caplifter, open can opener and open awl are perfectly fine. Everything displayed without the maximum bending possible.
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cy Offline dks

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Re: Extended implements: strain on the back spring?
Reply #10 on: January 26, 2022, 08:23:44 AM
The actual answer depends on many factors everybody above is ignoring.

Apologies from all above.

We were trying to provide simple quick answers, that do not seem to be up to the standard required.

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us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #11 on: January 26, 2022, 06:40:43 PM
Apologies from all above.

We were trying to provide simple quick answers, that do not seem to be up to the standard required.

I wasn’t in need of an apology.

Ironically, I viewed my answer as the quickest I could make to explain some things and misconceptions on the subject, beyond what is generally accepted as common knowledge here. There is quite a bit that could be expanded on regarding the whole knife and the relevance of liner widths and material and finish as well as rivet materials and temper used. Lots more could be explained about the spring seats, or maybe even just the more modern concave ones and how they affect the spring loads.

I only mean to educate and provide answers based on my personal knowledge and experiences. I’m sorry if you find that offensive in any way.

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cz Offline z1913

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Re: Extended implements: strain on the back spring?
Reply #12 on: January 26, 2022, 07:35:36 PM
Please trust that Victorinox actually made significant improvements over the years, and that we all benefit from these developments.


100% this. I have only my anecdotal evidence with comparison of older 108 GAK and new 111 Forester, but there was very tangible difference in feeling how the implements opened/closed - in the end I sold the GAK and kept only the Forester. It just felt so much better in use.

And thanks Kamakiri for you input - very informative.
« Last Edit: January 26, 2022, 08:36:43 PM by z1913 »


us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #13 on: January 27, 2022, 03:34:53 AM
100% this. I have only my anecdotal evidence with comparison of older 108 GAK and new 111 Forester, but there was very tangible difference in feeling how the implements opened/closed - in the end I sold the GAK and kept only the Forester. It just felt so much better in use.

And thanks Kamakiri for you input - very informative.

 :cheers:  You’re welcome z1913, and thanks for saying so.  :)

Many people will understand based off their own experiences with knives of different eras and construction styles just like you did. Modders who have also seen the different parts evolve will understand a bit more, and perhaps the ‘why’ behind the changes.
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us Offline Singh

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Re: Extended implements: strain on the back spring?
Reply #14 on: January 27, 2022, 01:01:37 PM
I'm always down for a deep dive into how things work.

that said, for me it all boils down to: open tools when you use them. close when not in use. When it wears out, replace it.
« Last Edit: January 27, 2022, 01:18:54 PM by Singh »


us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #15 on: January 28, 2022, 06:01:41 AM
An example of some changes in the Magnifier/Phillips/Lite Module backspring.

Note how the seats are completely different.

The samples are from ‘78, ‘04 and ‘16. (Generally gray, plastic lens, new glass lens variants). Significant spring variants are also in the ‘80s and ‘90s, but not really different regarding the tool and seat interaction. They are more for assembling details. Like to prevent squeezing at the 4th pin…which only one of the springs shown does on its own.

I’d show more, but I don’t have any of those types loose at the moment.
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nz Offline Sawl Goodman

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Re: Extended implements: strain on the back spring?
Reply #16 on: January 28, 2022, 08:10:46 PM
I have a story that may or may not be relevant to the topic.

Some years ago while fidgeting with a Sportsman, I opened the openers & awl at once. As I closed the tools I found the flat SD/cap lifter had lost all its snap.

Searching here, the general feeling from similar complaints was the spring had been damaged. It felt like a reasonable explanation & I was resigned to its new, permanent state.

Then I found a thread in which someone else found similar lack of snap in a tool. IIRC another member posted that the pin was more likely to have been bent instead. It made some sense to me as the 84mm pins are thinner than 91mm ones. The poster then suggested opening the tool, standing the knife vertically with the other end of the knife on a hard surface, & gently hammering the tool. I tried it on the Sportsman’s flat SD (with a wooden block on the end of the flat SD) - & wouldn’t you know, the snap was restored!

I feel this issue is more likely when opposite tools are opened together with a back tool. As KK says, with the opposite tools at 45 & 135 degrees the spring is squeezed to its maximum extent, thus putting considerable pressure on the pins. IME the cap lifter has the weakest snap of any tool anyway.

HTH in case anyone else has suddenly lost a tools snap.
Rambler


us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #17 on: January 28, 2022, 08:45:05 PM
 :tu: Absolutely relevant, Sawl. Pins are certainly more likely to deform before backsprings. And 2.2mm pins are more prone to it than 2.5mm end pins. 84mm knives and their 3-tool layers are definitely a concern for those 45° and 135° positions.

The fix you describe is similar to fixes I’ve used for restorations. But I’d suggest using punches on closed tools instead.  :)
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us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #18 on: January 29, 2022, 02:58:28 AM
Well, I can’t find any pics of it at the moment, but I’ve pulled pins from exposed pin vintage knives and it’s not rare to find ones that look more like crankshafts than knife rivets.
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us Offline kamakiri

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Re: Extended implements: strain on the back spring?
Reply #19 on: January 30, 2022, 03:00:44 AM
Found one.

This pin was well deformed on the main blade side and end of a 90mm c. 1950 234U. My finding is that the exposed nickel silver pins from this era are fairly soft and that spring compression forces are high enough to deform pins like this…when the springs don’t break. I haven’t broken any myself, but have several that I bought that way and they seem fairly common.

 Into the ‘50s, I've found it more common that the broad changeover from nickel silver to aluminum liners and harder tempered (usually brass) pins, caused more ‘broken backs’ where the liners crack in tension at the 3rd/back pin. Through the ‘60s I’ve found broken knives with either failure, broken backs being more common.

After 1970, I’ve yet to find a cracked spring. But broken backs are not uncommon with knives exposed to water or corrosive conditions.
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us Offline petey.grizz

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Re: Extended implements: strain on the back spring?
Reply #20 on: January 30, 2022, 04:01:12 AM
Fellow knights,

I wonder if any of you know whether leaving an implement extended continuously wears out the back spring? I would think not as Vic themselves are selling SAKs with extended implements (=large blades in its Damast collection), but I am not certain and would be curious to know. Thanks for any input!

Cheers,

Simon
Leaving them fully extended is no different than leaving them closed as far as the spring is concerned. Leaving them partially opened at angles aside from 90 deg will leave the spring under tension which will unload the spring over time. Another thing you will hear is that opening all the tools is bad. That is only if you open one on the same spring while the other is not fully extended, if that makes sense. With older vintage or particularly valuable knives I am either very careful or just do not display them with tools fanned out.
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