I don't understand why Spyderco pivots self loosen

[vivi]

Swapped my scales late last night and, this is on me, put off using loc-tite on the pivot.

Left the house with the pivot dialed perfectly. Just barely enough tightness to prevent a free swinging blade.

Use the knife a couple of times and notice it's now free swinging and there's generous side to side play.

Use the knife a few more times and realize I either need to stop carrying it for the day or go buy a torx set for until I get home.

You see, this is exactly how I cut myself on a tip up compression lock before.

Para 2 had the same issue. I had even used loctite on that knife but I guess the seal broke.

Pivot worked itself loose. Compression lock detent depends on the pivot screw tightness to function correctly. Loose pivot meant there was barely any tension on the detent. Knife came open in my pocket and sliced my hand.

I don't understand why this happens. I know I can fix the issue with loctite, which is why I bought some on my lunch break, but I don't run into this issue with any other knife. Not any other brand. Just Spyderco.

I carried a different brand the last few nights. I took it apart, cleaned and lubed it, sharpened it etc. before I carried it those few days. No loctite on the pivot. The pivot tightness is exactly where I set it a few days later.

Why can other brands hold the pivot tightness with no loctite for weeks but Spydercos loosen themselves after 20 openings?

Is this something that could be remedied by using different types of pivot screws?

It just seems silly having to worry about slicing my hand open at work over a pivot screw. There has to be a better way than being forced to loc tite the pivot screw any time an adjustment is made.

This has happened to me with the Military 1, Military 2, Para 2, Police 4 and more.

[Spyderwebs]

I recently had this happen on my 2 Ayoobs - I finally took them apart for a cleaning and tang polishing and upon reassembly I used blue threadlocker.

The blade pivot, lockbar pivot, and clip screws all loosened up within a couple days, 2 separate times (cleaning and reapplying blue locker each time). This is in spite of the blade pivot being a D shape which should prevent any rotation so I'm equally confused how this happens.

I was wary to use Red (permanent) threadlocker but ended up using it and that has held up fine now.

I'll find out if they was a mistake next time I disassemble I guess (mostly worried about the T5 screws).

[Paul Ardbeg]

I lost a body screw of my 940-1 and that one also had a loose pivot. It can happen to any brand from my experience. For this reason I alway use locktite on all screws including the pivot.

[Jesla]

Just a simple fact of physics…. When using a screw to secure a rotating piece at the pivot point, it will loosen as the piece rotates. You can peen the threads or use the preferred method such as a lock washer or thread locker. Lock washers and thread locker hold virtually all mechanical devices, be it a car or simple tool, together.

Once upon a time the lug nuts on the left side wheels on some cars were left hand threads to counter act to loosening of the lug nuts from backing out. At least until they figured out how to use studs that stretch, which uses the stretch of the stud to combat rotational loosening of the lug nuts.

There are self locking screws but they are expensive and hard to produce at the small scale that a knife requires. They also don’t like being removed and reused, much like a nylock nut.

[Skywalker]

I lost a body screw of my 940-1 and that one also had a loose pivot. It can happen to any brand from my experience. For this reason I alway use locktite on all screws including the pivot.

I'll second this - definitely not just a Spyderco issue. For most knives other than CRKs, if I'm adjusting the factory pivot position it's getting loctite or a little bit of teflon tape.

[RustyIron]

Screws remain tight because of the friction between the two thread surfaces. As the screw is tightened, the clamping force between the two surfaces increases, as does the friction. When the screw is not tight, clamping force is diminished, as is the friction between the surfaces. Further loosening is the result. A better question might be, "How is it possible that a loose pivot screw doesn't get looser?

[Evil D]

Did you give it time to set up?

Maybe try plumber's tape. I've used it before but think I prefer loctite. I'm using the blue chapstick loctite. I find it's easier to keep where I want it, I tend to use too much of the liquid and you really don't want that around the pivot. With the stick I hold the screw on the tip of my driver and scrape a little off with the threads and then turn the screw in my fingers so it smashes around into all the threads. You can still use too much and it'll squish out from under the screw.

It's also really important to try to remove all the old stuff between takedowns.

https://a.co/d/dGvOjID

[CDEP]

Did you give it time to set up?

Maybe try plumber's tape. I've used it before but think I prefer loctite. I'm using the blue chapstick loctite. I find it's easier to keep where I want it, I tend to use too much of the liquid and you really don't want that around the pivot. With the stick I hold the screw on the tip of my driver and scrape a little off with the threads and then turn the screw in my fingers so it smashes around into all the threads. You can still use too much and it'll squish out from under the screw.

It's also really important to try to remove all the old stuff between takedowns.

https://a.co/d/dGvOjID

Plus 1 on Evil D above.

Additionally, I usually wait until after a break in period to tweak the pivot and dab the blue chapstick loctite in there. Once adjusted with loctite I don't touch it for at least 48 hours.

Never had a problem this way, although I never flick open knives, so perhaps I'm not putting the same level of shock through the lock and pivot that fidgeters do.

I'm running the Military 2 BBB 15V as it came right now, because the action and edge bevel were perfect out of the box, and I haven't seen the pivot loosening. Will keep an eye on it because it will be months before I need to do my reprofile on it.

[ejames13]

What's even more irking is that many times they fail to apply loctite correctly at the factory, and this is especially true of Seki City. Golden models are usually better.

I've just accepted the fact that with every new knife, I'm going to have to remove at least the pivot screw and sometimes the stop pin / lock bar screw, apply loctite, and let it dry before the knife is ready to use.

In the grand scheme, it's a minor inconvenience I'm willing to tolerate.

[yablanowitz]

Screws remain tight because of the friction between the two thread surfaces. As the screw is tightened, the clamping force between the two surfaces increases, as does the friction. When the screw is not tight, clamping force is diminished, as is the friction between the surfaces. Further loosening is the result. A better question might be, "How is it possible that a loose pivot screw doesn't get looser?

Nice to see someone understands threaded fasteners.

[Halfneck]

I noticed this on my Brown FRN Delica recently. I noticed it dropped shut very easily when I depressed the lock compared to my newer Superblue Delica. There was also some *slight* side to side play. Tightened up the pivot & all is good. Could not even begin to tell you when the last time was that I tightened it.

Re: Other Brands - I have a Benchmade 531 Pardue that the pivot loosens up on quite a bit. Part of the reason being in how I open & close it. I never use the thumbstuds, instead I pull back on the axis-lock & flip it open & closed. Pretty sure that accelerates the pivot loosening up. I've also noticed it on an Emerson CQC7 with a wave device.

[VashHash]

I use Teflon tape most of the time. If that doesn't work then I use blue loctite and give it at least 24hrs to set. Almost every knife I own gets this treatment. Not just pivot screws either. Most of the time the Teflon tape works for the body screws. Loctite for clip screws and sometimes for pivot screws.

[N. Brian Huegel]

Over the last 30 or so years that I have been repairing Spyderco knives for customers (replaced a pocket clip or screw, tightened a screw, taken apart and reassembled for cleaning, adjust a pivot, etc.) I have always used red Loctite Threadlocker. Based on the hundreds of Spyderco, Benchmade, CRKT, Kershaw, Zero Tolerance, Buck, Gerber, etc. knives that we have worked on (an average 3+ per week) with loose or lost screws, they either have no Loctite (60%) or have blue (40%). This is why we always use red. Very, very rarely does a knife come back that we have worked on (and we see quite a few repeats especially for bent clips) that the screws have loosened with red Loctite. What seems most important when adjusting screws is to use a quality Torx bit (we prefer Wiha) and make sure it is properly seated in the screw head by tapping on the end of the driver with a light hammer (I have a 1”x1”x4” piece of bronze) as this helps to prevent the driver from camming out and damaging the screw head. If the screw will not budge with a moderate amount of force, we then apply heat via a soldering iron to break the hold of any Loctite. Two Cents!

nb

[Evil D]

Screws remain tight because of the friction between the two thread surfaces. As the screw is tightened, the clamping force between the two surfaces increases, as does the friction. When the screw is not tight, clamping force is diminished, as is the friction between the surfaces. Further loosening is the result. A better question might be, "How is it possible that a loose pivot screw doesn't get looser?

Nice to see someone understands threaded fasteners.

It's a good point and makes sense when you think about how bushing pivots work, you almost never completely tighten them down all the way or else you can't move the blade, so by definition the pivot screws are never actually "tight". I think this is why they always used red loctite, so the average user that doesn't fiddle with their knife never has to worry about this.

I don't recall ever having a loose body screw when I use loctite and it's most likely because those do get tightened all the way tight.

[Fastidiotus]

Even if they were tighted all the way the screws in a knife are experiencing torsional forces which would cause any nut/bolt/screw to loosen. The pivot also carries an extra force of shear stress every time the knife is used.

Loctite and locking nuts/washers exist because all threaded fasteners will succumb to these forces, and usually very quickly. If fastners didn't loosen frequently there wouldn't be such a huge market for trying to stop it from happening.

[Mushroom]

This makes me wonder if a torque wrench might be useful to help actually quantify knife pivot tightness.

I'm surprised knife enthusiasts haven't adopted torque wrenches yet. Maybe some have but they're not that common from what I've seen. They're much more common place in the bicycle industry by comparison.

There may not be a standardized torque setting that can be applied to all knife pivots but knowing the most appropriate torque settings for the screws on our own respective knives during assembly might prove beneficial.

With a torque wrench, for example, we can determine if 3Nm is too loose and results in blade play or maybe 6Nm is too tight and makes the action too stiff. Once we determine what the most appropriate torque setting for our respective knife is, we can use that as a repeatable value to aim for when doing maintenance. Might also provide a good baseline for body and clip screws to reliably avoid the risk of over-torquing and potentially damaging them.

[yablanowitz]

Believe it or not, the factory does use torque limiting drivers during assembly. But it seems most people around here don't believe in torque specifications or sequences. They'd rather pretend such things don't exist so they can do things any way they want and complain about the results.

[Scandi Grind]

I don't use a torque wrench because the tension I want is determined by how the blade moves, not by a torque spec. I just use Loctite in order to keep it where I want it and have never had an issue. I think letting the Loctite set, and cleaning old Loctite off before re-applying may solve most instances where blue Loctite was unsuccessful, however, if you can get red Loctite screws out consistently, I imagine the red should be more than enough to maintain the desired tightness.

[Evil D]

This makes me wonder if a torque wrench might be useful to help actually quantify knife pivot tightness.

There's a video out there somewhere of a Spyderco employee assembling knives using a torque driver.

[Mushroom]

Believe it or not, the factory does use torque limiting drivers during assembly. But it seems most people around here don't believe in torque specifications or sequences. They'd rather pretend such things don't exist so they can do things any way they want and complain about the results.

I definitely believe it's done that way from factory - I would actually expect it - but I can't recall ever reading recommendations for using them from individuals doing their own knife maintenance.

I wonder if Spyderco would be willing to publish the torque specs they use during assembly even though they also tend to discourage disassembly. Maybe publishing those numbers would send a conflicting message about disassembly. They're not exactly numbers that need to be safeguarded as some sort of proprietary trade secret though. Who knows maybe Spyderco introducing those numbers to the general public would be the catalyst for a shift in the mentality of how people maintain their knives.

I don't use a torque wrench because the tension I want is determined by how the blade moves, not by a torque spec. I just use Loctite in order to keep it where I want it and have never had an issue. I think letting the Loctite set, and cleaning old Loctite off before re-applying may solve most instances where blue Loctite was unsuccessful, however, if you can get red Loctite screws out consistently, I imagine the red should be more than enough to maintain the desired tightness.

That's why I question if actually knowing the particular torque spec of your desired "blade movement" would help to be able to repeat that action during future maintenance. If judging by feel alone is sufficient enough for our personal needs, that's fine, it clearly works but I also don't see a disadvantage to the capability of quantifying it.

This makes me wonder if a torque wrench might be useful to help actually quantify knife pivot tightness.

There's a video out there somewhere of a Spyderco employee assembling knives using a torque driver.

I believe it! I'd be interested to learn the torque numbers that they're using.