Why do some blades not align with the springs?

JB in SC said:
Jack Black Jack Black ugh that's awful..
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And a very good example of what I was talking about. The question is, is that what the OP was talking about?

I have a few that were worse than that when I got them. After correcting them they look much better, but the springs are sunken in the open position.
 
I think this is another example of the "cant" the OP seems to me to be describing:
4fTe8cj.jpg

I do NOT think this example was intentional. (Notice how the line on the tang - don't know the technical term - is not parallel to front of bolster. Looks like the "face" of the tang where it meets the spring wasn't ground adequately.)

BUT, I've looked at quite a few of my knives this morning, and some cant is not at all unusual, at least as I've tried to detect it. I tried placing a knife on its back spring on a flat surface (cutting board in the kitchen that I could pick up to eye level) and checking if the blade spine was also flat on the surface. Because many of my knives have some curvature to their backs, I decided to position each knife so the back of the pivot bolster was flat on the board and then check the blade spine's alignment. I found that MANY of my knives had spines that did NOT contact the board (and the gap between spine and board increased with distance from the bolster). And I don't think these are all defective; most of them seem to me to be by design.

An interesting case is the canoe pattern, of which I have many. Both spear and pen blade appear to "droop" significantly on every one I've checked, and I think that's the maker's intention. But much of the "droop" is an illusion caused by the handle curvature. If I position a canoe so the back of a bolster is flush with my board, the spine of the corresponding blade is actually quite well-aligned!

- GT
 
5K Qs 5K Qs
I have a hilarious image in my mind of a wife walking in as you check for blade cant and muttering " What the heck is he doing now?"

I have an Old Timer stockman that the sort blade is quite off. However, I find it advantageous in furbearer skinning and it gives a perfect angle in relation to the upsweep of the belly. It may very well be intentional on this knife.
 
black mamba said:
The trouble with that is, that it's very difficult to reach the surfaces that need to be filed without filing something you don't want to touch.
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The other thing to be aware of is, the backspring may drop below flush as well, with blade opened, if either the rear of the blade tang or the end of the spring is filed to compensate for the 'droop' ('cant') in the open position. It has the same potential impact on spring height as filing the kick on some blades, though at the other end of travel.

I filed the rear of the tang on a Case Peanut's clip blade, to fix just such a 'droop' in it's appearance when open. I'd seen another thread (link below) posted by member 'Gary W. Graley' mentioning the issue, also with a Case Peanut, which is what inspired me to look at my own. If I recall correctly, I used one of my DMT credit card hones to get in the narrow space behind the tang, with the blade propped to about ~1/3rd open for best access to the tang. I used a wine cork wedged in between the blade's edge and the handle, to keep it from snapping shut (Case Peanut's tangs are half-stopped, so they want to slam shut if not opened to at least the half-stop position). The spring did drop noticeably after filing, though I was more willing to live with that, than with the drooping blade. So, one has to choose whether it's worthwhile or not.

https://www.bladeforums.com/threads/case-peanut-blade-angle-adjustment.1173862/
 
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Jack is correct in his remarks about the terms under-bladed and over-bladed.
These conditions are determined with the blade in question open.
If the spring sits higher than the blade tang, this is called "under-bladed".
If the tang sits higher than the spring, this is called over-bladed (too much blade tang!).
Excessive wear on the rubbing surfaces of the tang or spring can cause this appearance.

As to the other condition, blade sag, cant or droop, it is actually hard to determine sometimes.
First glance on this Sowbelly, creates the impression of blade droop/cant.Droop 1.jpg Droop 2.jpg But if you consider the first inch or less of the handle adjacent, you can see the blade is fit correctly!
If this blade was raised at all, the blade would look awkwardly bent back, and frankly, clumsy and ugly! The benefits of this particular pattern are; semi-sunk joints, easily gripped handle, and minimal "hot-spots"! To my eye, it's a beauty!!
 
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In my opinion the joint should be in line, ever! If by design some drop might be required it has to be obtained otherwise.
Just have a look at some Bose's example, you'll find the drop but the joint is flat.
It stands true even with fixed blade knives, if the spine of the blade doesn't meet the handle at 180° it looks like odd/crooked.
Don't misunderstand me, the whole knife might be curved (i.e. swayback) as well but the junction should be 180° tangent....no broken backs!!!
 
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