Slipjoint tuning - am I too picky?

[quattromori]

Hi folks,
from my holiday's nest, while I relax, I also think alot...so here comes a new thread, and the hope for some good feedback (this forum never fails to do so).
I know this thread is walking the line with the maintenance forum, but since it's only focused on slipjoints I decided to post it here. If the mods disagree, then it will be moved, of course.
So...
Let's assume that (hypothetically) I have a slipjoint, and I like it very much...except for one thing: the spring tension. Now, I've mentioned it before, I hate strong pulls. I don't want to discuss whether a strong pull is better than a soft one, or the opposite. On this very topic, I have my thoughts very clear.
The question is: would it be possible (not to me, obviously, but to someone who knows how to do it) to disassemble the knife and modify the backspring to make it softer? or it does depend too much on the very design of the backspring, so there wouldn't be much difference? Is it possible to "remove" the half stop feature (rounding the tang) or that would imply to exchange the backspring with a new one made on purpose? has any of you guys thought about doing anything like this, or even had it done?
Or am I just too picky?

Fausto

 

[pertinux]

Fausto,

You are too picky.

Just kidding; we almost are all particular about something (even about not caring about certain attributes), it just shows in different ways!

I'm wondering if there might be some middle ground and/or less intrusive attention paid to the knife in question, that might bring about the desired result?

I've written before about Bill Howard's easing the spring tension on the secondary clip blade of my #25 Jack when I was the GEC factory last July. Here's ea42's explanation (in response to someone else's question in that, which I didn't know how to answer) of what Mr. Howard most likely did:

Pertinux, the point on the backspring right at and a bit forward of the center pin is where most of your spring tension is. To relieve some of the tension you just need to remove a bit of material from the spring at this point. That's likely what Mr. Howard did from the sound of it. You have to be careful, it doesn't take much to make the spring too weak, which is why he likely didn't want to mess with the 26, what you remove from one spring has to be removed from the other as well. Normally when a knife is assembled the springs are oversized and stick up above the brass scales (talk about a nail breaker!!). When it's ground and hafted the object is to grind the springs down to the scales and stop there, that's generally where the ideal spring tension is, or at least where it was designed to be.

So, it sounds like it might be possible for someone skilled to ease the knife's pulls, to bring them more to your liking? However, note the bold (mine) above-- hopefully someone here will know if it's worth the attempt.

~ P.

 

[quattromori]

P.,
thank you for your answer. I didn't remember such topic discussed on this forum.
Honestly, I don't think that any "non-invasive" action could really make me happy.
As for the half stops, I'm even more clueless

Fausto

 

[pertinux]

Honestly, I don't think that any "non-invasive" action could really make me happy.

I hain't touching that one.

But I will again note, Bill Howard was gone for maybe 10 minutes with my knife, 15 at the most, and his ministrations made all the difference between a mondo stiff little bugger ('cause I know Frank likes that description) and a blade that opens with ease.

The half-stop situation definitely sounds more challenging.

I'll hush now and let those who know what they're talking about respond.

~ P.

 

[kc custom]

It is possible by disassembling the knife, with a 3 point set up in a small vise you
can either add more or less tension to a spring. will put a pic up shortly.
Ken.

 

[kc custom]

In the first pic the spring is in an overbent "backwards"- taking tension off.
The second pic just the opposite. This works on springs @ Rc 47-50 but needs
a bit more of a gentle touch on blades. In the second pic where the pin is contacting
the inside the spring metal removal would do it too. Ken.

 

[kc custom]

On the half stop lets say you had a.035-.040 preload on the spring, you could radius your corners
more to smooth it out, but without a way to add metal to the flat of the half stop you would
be better off with a new blade.
Ken.

 

[neeman]

Ken,

I have left my blade open on the spring for a couple of days
It seamed to ease the pressure on the opening

Is this fact or fiction?
Was I just lucky or does it work?

 

[Jack Black]

STILL on holiday??!!!






Hope you're having a great time Fausto!

 

[knifeswapper]

I doubt Bill did any metal work on the backspring for pertunix, if for no other reason than just the time constraint. You can't pull a backspring without breaking the bone, or at least damaging it a bit. I guess if you had bolsters on both ends you could free the ends of the spring and swing it out and trim some off the end for clearance only. But this would cause an integrity problem in spring steel, as well as causing it to be below the liner on the other side, and I don't see him doing that. I would expect either a little backward tension as Ken shows, but in an assembled knife state, or a little expert shaving on the tang would solve a majority of the concerns.

But to the OP, I expect after ruining a couple dozen knives (and the right equipment), you would be able to alleviate tension in some cases. You will be amazed at what problems show up in fit once you fix something else. Also, building a new backsprings would be an effort in futility for most mortals. Putting a radius on a square back end may also be beyond what is reasonable - they could be softened right at the square but completing a full radius would probably affect too much of the front/back edge to sit properly in open/close position (spring below liner on backside). Again, something that could probably be accomplished with a lot of trial/error.

But I guess it needs to be said, that any of this type work would void a warranty.

As for neeman, the factory would probably say that if you relaxed their spring steel in a few days (or months) by half open blades, they need to have a serious talk with their heat treat guy But perception is reality, and if it seems better then it is better. I have pulled Case knives from 40 year old display boards that would still snap like a gator and that would have to be pushed closed. But I don't know how they went on the board, so this one is a mystery to me.

 

[TLARbb]

There is some chance that there is some relaxing of stress in the spring by being put in a partially opened position. It seems that relying on such a situation would be pretty much "iffy". However, putting the knife in that condition and pinging the backspring with very light hammer taps (tack hammer) might hasten an stress relieving in the spring. I am certainly no expert in this area, but I do know there is the phenomenon known as "creep".

However, knife springs are designed by the maker to operate in the "elastic" region of the stress/strain relationship and a stress relieved spring should not change tension on the blade by sitting for a few days or weeks in a deflected condition. The operations of rolling sheet stock at the steel mill, stamping or cutting parts from the stock and heat treating the material after forming all introduce some "stress" in the spring. The knife makers here know this much more personally than I as they work with these materials, processes, and assemblies every day.

I would think that smoothing of the mating surfaces of the blade and spring, thus reducing the static and kinetic friction would make a larger difference in most knife assemblies. Smoothness of the parts and lubrication can make an order of magnitude difference in the force needed to open a knife.

Ed J

 

[midnight flyer]

As for neeman, the factory would probably say that if you relaxed their spring steel in a few days (or months) by half open blades, they need to have a serious talk with their heat treat guy But perception is reality, and if it seems better then it is better. I have pulled Case knives from 40 year old display boards that would still snap like a gator and that would have to be pushed closed. But I don't know how they went on the board, so this one is a mystery to me.

I think basic engineering and understanding of the mechanics of a spring would bear that out very easily. By the design of any spring as a mechanism, they either get weaker as they wear, or break because the wear out. In the life expectancy of a slipjoint spring mechanism, what is the actual wear load of a few hours with no compression/expansion cycling? We know that backsprings on most knives will easily last 50 years with regular use, so I don't think a few hours of no movement will net anything measurable. All springs have a life expectancy, and based on their duties and use, it varies widely. They are designed and engineered to perform to a specific task, however they will not find their own sweet spot in which to operate. Springs are designed with one function in mind, and that is to create or control movement.

You can prove what you are saying in a very easy way, though. No math or science needed. Just take a minute and imagine what the folks are saying that believe that leaving a knife open or half open for a few days or weeks are saying when they declare the spring has lightened up. They are saying that the spring is starting to fail. To continue with that line of thought, your knife would fail in very short order as you would wear out the knife with a couple of years with normal use as the spring lightened up from its normal duty of compressing and expanding.

So to say that "I left the knife open for a couple of days that spring was lighter" makes no logical sense at all unless you have an improperly made spring. The only way you can reduce the load on the spring of a knife is to bend the spring or remove metal from contact surfaces.

However, knife springs are designed by the maker to operate in the "elastic" region of the stress/strain relationship and a stress relieved spring should not change tension on the blade by sitting for a few days or weeks in a deflected condition.

I would think that smoothing of the mating surfaces of the blade and spring, thus reducing the static and kinetic friction would make a larger difference in most knife assemblies. Smoothness of the parts and lubrication can make an order of magnitude difference in the force needed to open a knife.

Ed J

Couldn't agree more. The first statement means the knife was properly engineered and properly executed in assembly.

The second is common sense. While I have not relieved any psi of tension on the backspring of a knife by disassembly, I have made it smoother and easier to operate with a good cleaning and sticking the skinny wheel of my Dremel in to polish the the tiny part of the spring contact area of the blade when the knife is closed. Can't get anything small enough to do that on a small knife, but on a large knife it seems to help a bit sometimes. Mostly though, the knives I have had have become more smooth by the contact areas self polishing by the use they get from repeated opening and closing when well lubricated.

I bought a Queen CC from Mike a few years ago that was pretty rough on the opening and closing, and was also really hard to open due to a heavy spring. I put good old fashioned 3in1 oil on he joint and opened and closed it about a thousand times. Did it again the next day. The spring tension is no different, but the contact area shines like it was polished with jeweler's rouge, and the knife is a smooth as silk to open. Still has a really snappy spring, but opens and closes nicely since it doesn't have any binding points.

Robert

 

[pertinux]

So to say that "I left the knife open for a couple of days that spring was lighter" makes no logical sense at all unless you have an improperly made spring.

Yet, that's exactly what Bill Howard at GEC recommended I do with my #26 (in lieu of his addressing the spring directly, as he was hesitant to do), showing me the angles at which to leave the blades.

I have no sense that he was humoring me, and nor would I think he was misinformed...?

Hunh.

~ P.

 

[quattromori]

Ken,
Thank you for your posts, and for your pictures as well. An answer from a skilled knifemaker is all I could hope for.

Mike,
There is no way I will ever try to do such thing on my own. I know how far I can go, and it would still be miles away. I never really believed that opening and closing a knife many times, or leaving it half open, would ease the tension, although opening and closing it many times could help removing some metal powder "trapped" in the friction area, thus producing a positive effect (although cleaning and lubricating it properly will have the same effect). but nothing more than that.

Now I have to decide what to do with the knife, but it's good to know that, at least, there is a way to get some result, at least on the backspring issue. I might talk with the factory and see if they offer any solution, cause I'd really love to carry this knife, and I'm afraid that sooner or later the stiffness of the backspring will make me leave the knife at home.
As for the half stop, I will probably have to live with it. Either way, half stops combined with a softer pull don't bother me as much

Fausto

 

[C Ben Susrool]

Ken,

I have left my blade open on the spring for a couple of days
It seamed to ease the pressure on the opening

Is this fact or fiction?
Was I just lucky or does it work?

Certainly seems to have worked for me on more than one knife.

 

[kniferbro]

So to say that "I left the knife open for a couple of days that spring was lighter" makes no logical sense at all unless you have an improperly made spring. The only way you can reduce the load on the spring of a knife is to bend the spring or remove metal from contact surfaces.

Leaving the knife open would definitely not reduce the spring tension but leaving it partially open, as to raise the spring, would. As you said over 50 years of using a slippie, it can retain the tension in the spring, but if you isolate the time during all of that use where the spring is actually being stressed (raising the spring on the back of the knife) it would amount to fractions of a second for each opening/closing. Leaving the spring stressed for 3+ hours would mimic years to a lifetime of actual use.

 

[confucius37]

I have left a few slipjoints partially open for a few days at a time and it seemed to help a little bit. The change was not drastic, but it was noticeable at least to me, enough that I felt much more comfortable carrying the knife.

 

[knifeswapper]

Ken,
Thank you for your posts, and for your pictures as well. An answer from a skilled knifemaker is all I could hope for.

Mike,
There is no way I will ever try to do such thing on my own. I know how far I can go, and it would still be miles away. I never really believed that opening and closing a knife many times, or leaving it half open, would ease the tension, although opening and closing it many times could help removing some metal powder "trapped" in the friction area, thus producing a positive effect (although cleaning and lubricating it properly will have the same effect). but nothing more than that.

Now I have to decide what to do with the knife, but it's good to know that, at least, there is a way to get some result, at least on the backspring issue. I might talk with the factory and see if they offer any solution, cause I'd really love to carry this knife, and I'm afraid that sooner or later the stiffness of the backspring will make me leave the knife at home.
As for the half stop, I will probably have to live with it. Either way, half stops combined with a softer pull don't bother me as much

Fausto

I honestly think everyone that is as finicky as you and I should buy a few $5 knives and play with them (trying to tune to our desired outcome). First, it is an eye-opener. Second, you might be able so figure out just how to suit yourself on those little things that bug you in the future.

For all that feel like leaving the knife open in the most "backspring stretching" position for a few days helps; it is good to hear. But if you had some scientific way to measure it, I am afraid we would be disappointed at the true result. I'm not going to go as far as some and say there is no way; but I know every factory I have ever asked the same question laughed at me.

 

[quattromori]

Mike,
you are right. I'd like to be able to tune such things in a knife. But since I can't, and possibly will never be able to do it, I still search for options and ways.
And meanwhile...I'm just picky and I like to bring such topics into talk.

Fausto

 

[midnight flyer]

For all that feel like leaving the knife open in the most "backspring stretching" position for a few days helps; it is good to hear. But if you had some scientific way to measure it, I am afraid we would be disappointed at the true result. I'm not going to go as far as some and say there is no way; but I know every factory I have ever asked the same question laughed at me.

Having dealt with Mike for years now and actually had these types of conversations on the phone, I can tell you he knows more about slipjoint knives than just about anyone I have met or spoken to about issues and problems. I now that he has been in business for sometime and provides his no BS 100% customer satisfaction as part of his business I would imagine he has seen it all and done it all with production knives and their problems.

That being said, I will go with his statement about the subject. Plenty around here know more about knives than I do even after carrying and using slipjoints for a few decades now.

Still, since a backspring on a knife is under compression when it is closed, likewise when it is open (in other words always) I don't understand how a few hours/overnight/few days of half open will weaken the spring so much that there is a noticeable difference in operation of knife, and as mentioned above, duplicate a lifetime of use. Since the spring cannot think on its own and has no built in mechanism as a fail safe, then using that same logic to compute the trajectory of spring life, you might be able to leave a knife open for several months or a year and it would have a completely worn out or broken spring by the time you decided to check it.

May have to chalk that one off as one of the things I just don't understand.

Robert