Using flat punch on weak backspring?

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lithicus

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Feb 24, 2022
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I apologize if this is not the appropriate place to post this. Please remove this thread if I'm violating any rules.


So, I recently given a used USA 34OT. While the snap is strong on the spey and sheepsfoot, the snap on the clip is non-existent.

I'm not familiar enough with knives to disassemble and reassemble one. Especially one with swinden keys. Not to mention I don't have a donor spring or a cheap/easy/worthwhile way to acquire one. So, I was looking around for another way to potentially address this issue short aside of just pushing the blade all the way open/close every time I may want to use the clip.

I found a comment in a thread by S shecky stating:
The "proper" way is to unpin it and get a new spring fabricated or try to re-temper the old one. One could try slightly bending the original spring to add tension. Either way, big pain in the neck, costly, relative to the original knife.
The hack way is to use a flat punch of some kind, a hammer, and some kind of steady like an anvil, to slightly bend the spring without disassembly. This is of limited usefulness, and can easily destroy a knife as fix it, especially if unsure or not careful.
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They haven't been online in nearly 2 years, however. So, I don't think I would get a response in a DM.

Can anyone clarify this "hack"? I'd be willing to try it as most of the work I've done on knives so far has been successful (ie; re-centering blades by crinking, fixing blade wobble with vise/peen/sanding flush, filing kicks).


I guess my gut instinct says the flat punch needs to go on the inside of the knife. I imagine you're trying to "bow" the spring in such a way to put more tension on the pivot/tang. If the flat punch went on the outside/back/bottom of the knife, it seems like it would bend the spring the opposite direction you'd want and flatten it out; creating less tension. I also imagine you'd want a pretty small flat punch. If it were too wide, you'd just blow the spring out and likely break the pins.

I know that I may ruin this knife by trying, as stated in the post I linked. But, I think it is worth it to me for the learning experience alone (albeit I'm not quite ready to jump into a full disassembly / reassembly just yet).

Thoughts? Ideas other than "just carry it as is"? Thanks!
 
Since that clip blade is on it's own single spring, it may be that the clip blade was used (A LOT), and that the tang is worn down, leading to weak spring tension. In theory, the "bend the spring" method may add some tension, but does require taking the knife apart. I'd investigate further, comparing the two blade tangs that are on the same end, to see if they look about the same height, or if the clip has obvious excessive wear.
 
I did already compare a well working 34OT to this one and it does seem there is a good amount of wear on the tang. Especially the "closing corner", if that makes sense. The backspring hardly moves when opening and closing. I thought, perhaps, that with a bit more spring tension it might work better or well enough. But, your statement does make me wonder if the only real fix might be to replace the clip to get a fresh tang. It seems, and rightfully so, that you are pointing out that the issue may not be with the backspring at all; which honestly makes a lot of sense.

I almost always carry my knives in slips. So, I'm not worried about cutting myself or anything. Just thought, especially since this knife was free, that I'd take it as an opportunity to further my ability to work on knives. Maybe I'll just have to wait until I get another junk 34OT and use the parts from both to make a working knife 😅
 
The correct way to bend the spring a bit is to take it out of the knife, prop the working end up on something and give the spring a whack near the center pin. That'd give it a bit of a bend just before the center pin since that's usually the thinnest part. You could attempt to prop the knife up in a similar way and use a punch between the center pin and the blade, but I don't think that would work as the spring is pretty much locked in place in that position. I think all you'd wind up doing is bend the center pin and crack the covers. On a conventional pinned knife you wouldn't have to completely take it apart to make the bend in the spring, just remove the center pin and pivot the spring away from the knife. With the swinden key, removing the center pin will allow you to take the knife apart without any additional effort, which is a good thing. They're easy to reassemble as all you really have to deal with is putting in a new center pin. Since it's a junker give it a try. BTW if you've got tang wear you also have spring wear, so the cost of having someone replace both would probably equal the cost of getting a similar knife in better shape.


Eric
 
Wow... such a very informative post!! Thank you very much!

I agree that trying to use a flat punch to bend the spring without removing any pins sounds like trouble. That's kind of why I asked because I wasn't exactly sure what the poster in the linked thread was talking about.

I may try to remove the center pin on this one and see if I can bend the spring without replacing the clip. Worst case scenario, I end up with a parts knife. Best case scenario, there's at least a little bit more tension with the clip. I'm afraid the clip tang might be too worn to see any improvement, however. I feel like I have seen people "mod" the swinden key with a pivot pin on these schrades. If all else fails and I can manage to get another 34OT parts knife, maybe I can try to swap a better clip for this overly worn one and put a pin through the bolsters and pivot. It sounds like a fun project at least! hahahh

Edit: I just realized that unless there is blade play there is no need to put a pin through the bolster. The swinden key makes it very easy to disassemble and reassemble by only replacing the center pin. I might have to give this little project a shot!
 
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ea42 said:
The correct way to bend the spring a bit is to take it out of the knife, prop the working end up on something and give the spring a whack near the center pin. That'd give it a bit of a bend just before the center pin since that's usually the thinnest part. You could attempt to prop the knife up in a similar way and use a punch between the center pin and the blade, but I don't think that would work as the spring is pretty much locked in place in that position. I think all you'd wind up doing is bend the center pin and crack the covers. On a conventional pinned knife you wouldn't have to completely take it apart to make the bend in the spring, just remove the center pin and pivot the spring away from the knife. With the swinden key, removing the center pin will allow you to take the knife apart without any additional effort, which is a good thing. They're easy to reassemble as all you really have to deal with is putting in a new center pin. Since it's a junker give it a try. BTW if you've got tang wear you also have spring wear, so the cost of having someone replace both would probably equal the cost of getting a similar knife in better shape.


Eric
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It's really cool to have someone, such as yourself, that has this experience to guide us. 🤠 :thumbsup:
 
I think it’s possible to see some improvement by using a punch, if you supported the spring at the pin and at the end. I don’t have any experience though. If it was supported at the pin, it wouldn’t put any stress on the pin.
 
JM2 said:
I think it’s possible to see some improvement by using a punch, if you supported the spring at the pin and at the end. I don’t have any experience though. If it was supported at the pin, it wouldn’t put any stress on the pin.
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Yea, this was the only thing I could think the poster from that thread meant in the link I mentioned. And it certainly is a hack and not the right way to do it.

I'd think you'd want a punch that is sized roughly 1/2 the distance between the center pin and the pivot. Maybe a little less. Center the punch in the blade well between the center pin and the pivot and make sure everything is well supported. Hit it until the spring has more tension.

But as I'm thinking about it, this would likely make the spring proud in between the center pin and the pivot. Filing it back down flush would weaken the spring, undoing at least some of the work you just did.

It's an interesting thought, idea, or experiment, but I'm not sure how well it would actually work in practice.
 
i haven’t considered the spring would be proud on the back. I’d say you’re correct.
 
lithicus said:
Yea, this was the only thing I could think the poster from that thread meant in the link I mentioned. And it certainly is a hack and not the right way to do it.

I'd think you'd want a punch that is sized roughly 1/2 the distance between the center pin and the pivot. Maybe a little less. Center the punch in the blade well between the center pin and the pivot and make sure everything is well supported. Hit it until the spring has more tension.

But as I'm thinking about it, this would likely make the spring proud in between the center pin and the pivot. Filing it back down flush would weaken the spring, undoing at least some of the work you just did.

It's an interesting thought, idea, or experiment, but I'm not sure how well it would actually work in practice.
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You want the spring to bend toward the center of the bolster. With the blade in place it can't move in that direction no matter where you hit it. What'll happen if you do it as you describe is you'll just put a bump in the spring that'll stick out beyond the liners, and at the same time not add any tension to the spring. That's if you don't wind up breaking the spring first.

Eric
 
ea42 said:
You want the spring to bend toward the center of the bolster. With the blade in place it can't move in that direction no matter where you hit it. What'll happen if you do it as you describe is you'll just put a bump in the spring that'll stick out beyond the liners, and at the same time not add any tension to the spring. That's if you don't wind up breaking the spring first.

Eric
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After reading it worded that way, I agree totally.
 
ea42 said:
You want the spring to bend toward the center of the bolster. With the blade in place it can't move in that direction no matter where you hit it. What'll happen if you do it as you describe is you'll just put a bump in the spring that'll stick out beyond the liners, and at the same time not add any tension to the spring. That's if you don't wind up breaking the spring first.

Eric
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Why didn't I realize this 😂 It's almost too obvious and makes too much sense! Thank you for pointing this out!

I think it's safe to say now that you simply cannot fix a weak spring without taking the knife at least partially apart; even if you try to "hack" it.
 
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