Fixing loose backspring on NEW Case Barlow

[hsherzfeld]

My new Case Barlow (62009 1/2) arrived a few days ago with great walk and talk (although I'm not a huge fan of the half-stops). I've just finished dyeing the natural bone scales with leather dye. In the process of which, I opened and closed the blades a lot to flush out excess dye, etc. I did run the knife under hot water in an attempt to make the scales absorb more of the dye. I also used a jeweler's file to slightly round the corners of the tangs that are exposed when the blades are folded, to make the transition from half-stop to full open more smooth. This did not affect the surfaces of the tangs that engage the springs (those surfaces still have the factory toolmarks that they came with).

But now, suddenly, the clip blade is slightly loose in the full-open position and very loose in the full-closed position, so much so that it rattles if I shake the knife while it's closed. It's only solid at the half-stop. It's as if the spring suddenly lost some of its tension and isn't engaging the tang surfaces. Meanwhile, the pen blade is still solid in both positions. I doubt that I can return the knife now that I've dyed the scales.

Any suggestions as to how to fix this issue? Is there a way to re-stiffen the spring?

 

[Bill DeShivs]

Not without removing the spring from the knife.

 

[Goose 7279]

My new Case Barlow (62009 1/2) arrived a few days ago with great walk and talk (although I'm not a huge fan of the half-stops). I've just finished dyeing the natural bone scales with leather dye. In the process of which, I opened and closed the blades a lot to flush out excess dye, etc. I did run the knife under hot water in an attempt to make the scales absorb more of the dye. I also used a jeweler's file to slightly round the corners of the tangs that are exposed when the blades are folded, to make the transition from half-stop to full open more smooth. This did not affect the surfaces of the tangs that engage the springs (those surfaces still have the factory toolmarks that they came with).

But now, suddenly, the clip blade is slightly loose in the full-open position and very loose in the full-closed position, so much so that it rattles if I shake the knife while it's closed. It's only solid at the half-stop. It's as if the spring suddenly lost some of its tension and isn't engaging the tang surfaces. Meanwhile, the pen blade is still solid in both positions. I doubt that I can return the knife now that I've dyed the scales.

Any suggestions as to how to fix this issue? Is there a way to re-stiffen the spring?

Which way is it loose? Side to side or up and down. If its side to side you can peen the pivot pin or maybe put it in a vise to tighten it up some you will just have to polish it up some afterwards

 

[Obsessed with Edges]

The corners of the 'square' tangs in folding knives with half-stops are important. They're essentially the most important part influencing the opening pull or closing pull of the blades, i.e., the pull which makes the blade firmly snap open or closed. I'd be willing to bet, rounding off the corners of the square tangs, even a little bit, is what's making it feel loose all of a sudden. Probably nothing wrong with the spring itself. Nothing about the dying or cleaning process should influence the strength of the spring.

The link below is a glossary of the anatomy of folding knives. Take a look at the explanation for the 'torque point' (opening and closing) line items in particular.

https://agrussell.com/knife-terms/blade-parts-slipjoint-knives

 

[hsherzfeld]

Which way is it loose? Side to side or up and down. If its side to side you can peen the pivot pin or maybe put it in a vise to tighten it up some you will just have to polish it up some afterwards

It's loose up and down.

The corners of the 'square' tangs in folding knives with half-stops are important. They're essentially the most important part influencing the opening pull or closing pull of the blades, i.e., the pull which makes the blade firmly snap open or closed. I'd be willing to bet, rounding off the corners of the square tangs, even a little bit, is what's making it feel loose all of a sudden. Probably nothing wrong with the spring itself. Nothing about the dying or cleaning process should influence the strength of the spring.

The link below is a glossary of the anatomy of folding knives. Take a look at the explanation for the 'torque point' (opening and closing) line items in particular.

https://agrussell.com/knife-terms/blade-parts-slipjoint-knives

That's what I'm worried about, but if it's the rounded torque points that are making it loose, it shouldn't be loose in the full-closed position because I didn't mess with the closing torque points, only the opening ones. The end of the spring is also no longer flush with the back of the knife like it used to be.

 

[Obsessed with Edges]

Regarding the spring no longer being flush, is that with blades open or closed (or both)?

Did you file the kick on the clip blade at all? Some will do this to adjust the height of blades in the handle, when closed. If so, that might also influence the tension keeping the blade closed, and also the backspring position (flush, sunk or proud) when the blade is closed.

 

[Goose 7279]

The corners of the 'square' tangs in folding knives with half-stops are important. They're essentially the most important part influencing the opening pull or closing pull of the blades, i.e., the pull which makes the blade firmly snap open or closed. I'd be willing to bet, rounding off the corners of the square tangs, even a little bit, is what's making it feel loose all of a sudden. Probably nothing wrong with the spring itself. Nothing about the dying or cleaning process should influence the strength of the spring.

The link below is a glossary of the anatomy of folding knives. Take a look at the explanation for the 'torque point' (opening and closing) line items in particular.

https://agrussell.com/knife-terms/blade-parts-slipjoint-knives

It's loose up and down.



That's what I'm worried about, but if it's the rounded torque points that are making it loose, it shouldn't be loose in the full-closed position because I didn't mess with the closing torque points, only the opening ones. The end of the spring is also no longer flush with the back of the knife like it used to be.

Im sorry to say Peening and using the vice will not help that type of play then. Obsessed with edges is right on the money. The squared edges of the spring are what engage the squared tang in the open and closed position. Its a learning experience im just sorry it happened to you bud.

 

[hsherzfeld]

Regarding the spring no longer being flush, is that with blades open or closed (or both)?

Did you file the kick on the clip blade at all? Some will do this to adjust the height of blades in the handle, when closed. If so, that might also influence the tension keeping the blade closed, and also the backspring position (flush, sunk or proud) when the blade is closed.

I have not filed the kick at all. The end of the spring is slightly proud (by a tiny bit, maybe a mm) in both the open and closed position. There doesn't appear to be anything in the way of the spring to prevent it from returning to the flush position: I just tried using pliers to force the spring flush (with blade full open) and managed to do so, at which point the blade no longer wobbled. But it won't stay flush after opening and closing.

 

[WValtakis]

Sounds like some rust may have formed after the dyeing process causing the spring to bind...I'd give it a good flush with WD-40 and work the joints.

 

[Obsessed with Edges]

Another thought...

Wondering if the filing left any bits of swarf (metal particles) to get embedded or wedged between the liner & backspring. If something's in there, it might be preventing the spring from moving through it's normal range of travel. Might be what's keeping it a bit proud of the handle, AND also why the blade action seems a bit loose now. Just speculating..., but it might explain a lot of this.

 

[hsherzfeld]

Another thought...

Wondering if the filing left any bits of swarf (metal particles) to get embedded or wedged between the liner & backspring. If something's in there, it might be preventing the spring from moving through it's normal range of travel. Might be what's keeping it a bit proud of the handle, AND also why the blade action seems a bit loose now. Just speculating..., but it might explain a lot of this.

That's my hypothesis as well. I might just be grasping at straws and hoping I didn't ruin a brand-new knife.

 

[Obsessed with Edges]

If there is some grit or swarf bound up in there, I'd just keep working the action open & closed, perhaps also while submerged in some water & dish soap (it'll be slippery, so be careful). Working the action might eventually dislodge the particle(s) and the soap & water will help flush that out if it comes loose. With dirt or grit in the action, that's about all that can be done, short of completely taking it all apart.

 

[jpm2]

I agree the spring is in a bind not fully engaging the tang in the open/closed positions. Sitting proud is an indication of this. Could be rust, grit, gummed up from dye, or whatever.

Does the spring raise and lower at all when opening/closing?
If not, it could be cracked/broke.

 

[hsherzfeld]

It does raise and lower. It holds the blade at half-stop just fine.

 

[hsherzfeld]

Just for kicks, here's the knife in question.

 

[hsherzfeld]

Update: I have managed to tighten the spring so that the blade only has very minor play in the open position. How did I do this? I put the knife in a padded vise (springs facing up), placed a flathead screwdriver tip against the proud end of the spring, and persuaded the spring to lie flush with taps from a rubber mallet on the screwdriver handle. The remaining blade play in the open position might very well be due to my rounding of the torque point, but I still can't account for the blade play in the closed position even with the spring flush. Anyway, the knife is usable again as far as I'm concerned.

 

[Obsessed with Edges]

I wonder if there was a burr left on the edge of the tang after filing. If so, it might keep the spring from seating fully flush against the tang when the blade is open. The tapping treatment with the mallet, to get the spring to seat more flush, sounds like it might've flattened or mashed the burr, if it was there.