Bent backspring?

MarkPinTx said:
In the grand scheme the number of cycles a backspring undergoes is relatively low, although I suspect the loading is medium to high. It isn't a super critical spring, but fundamentals of machine design should be observed, which, in addition to cost, means you don't see super steel springs.
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Thanks for the response. I love the geek side of metal working, but when I try to discuss it with anyone around here their eyes glass over. I agree that surface finish plays a large role in crack propagation, but given your last paragraph I wonder if it isn't a bit overkill.

Let's say you open or close a knife three times a day for twenty years. That's 6 cycles a day, 43,800 cycles over the lifetime of the knife. That doesn't seem a lot to me. Especially if the spring isn't exceeding the yield limit.

I just wonder if all this is just over kill in the cases of pocket knives. Do the stresses of a big spring also show up in a little sorting, like a back spring?

Feel free to email me if you'd like. I'd enjoy learning.
 
Well if a spring exceeds the yield stress of the material it's sprung so to speak. A million cycles is frequently used as a test of the fatigue strength of the material, that is if it survives a million it has effectively infinite life. But I suspect the stress on a backspring is relatively high, plus it stays relatively highly stressed constantly. Cracks form where there is a large enough defect in the material to let one get started. Stress causes small defects to migrate together to form a large enough defect to start a crack.
 
Also I have seen backsprings not crack, but just "go soft" and yield. Although with much handling the soft section will just break too. I'm not surewhat that failure is. Maybe an internal crack.
 
Right before Christmas I got my knife back. The spring was replaced or fixed, but the pull on the knife is about a 1, if that, now. I want to hang it upside down and see if the blades will fall open! I've seen old worn out knives with better pull than this. If it came back to me like this, then it is acceptable from the shop like this. Sending it back or contacting them would be pointless. Do I put it on the side as a letter opener, do I contact them? I'm in a quandary about this. They are still some of the prettiest made knives out there, often times prettier than other companies offerings, though not as well made. What do you think?
 
For starters, perhaps send an email directing someone from the company here, if only to note the 743 views this thread has already received...?

And counting. ;)


-- I would send it back (again), not because I had hope that whomever okayed the knife the first time(s) would do a better job next time, but to make it clear that this is not acceptable.

~ P.
 
silenthunterstudios said:
Right before Christmas I got my knife back. The spring was replaced or fixed, but the pull on the knife is about a 1, if that, now. I want to hang it upside down and see if the blades will fall open! I've seen old worn out knives with better pull than this. If it came back to me like this, then it is acceptable from the shop like this. Sending it back or contacting them would be pointless. Do I put it on the side as a letter opener, do I contact them? I'm in a quandary about this. They are still some of the prettiest made knives out there, often times prettier than other companies offerings, though not as well made. What do you think?
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pertinux said:
For starters, perhaps send an email directing someone from the company here, if only to note the 743 views this thread has already received...?

And counting. ;)


-- I would send it back (again), not because I had hope that whomever okayed the knife the first time(s) would do a better job next time, but to make it clear that this is not acceptable.

~ P.
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Exactly this^^. :thumbup:

Queen needs to make this right, and they also need to be made fully aware it shouldn't happen at all, in a 'repaired' knife. If, for some reason, they can't repair it correctly, they should at least replace it with a new one that's up to par.


David
 
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I'm not a proponent of sending knives back Dan but in this case I would simply to make a point as Sarah and David have said above. I would even go so far as to contact Ken Daniels to bring this sub-par repair to his attention.
 
Yes, it's really poor, no excuses for this it has to go back. Unless of course you want to go from slipjoint to friction folder....Three blade friction folder:eek::mad:
 
I'm surprised that no one has told you that your expectations are just too high, that perfection is not attainable or to be expected in a production knife, and that people like you will be the death of America's last great cutlery companies. It still cuts - don't it ? ;) :D
 
I just know that Queen can do better than this. I'm going to talk with Ryan Daniels, see if I can send them to him directly for his determination.
 
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