Which is the stronger stop pin?

[Charlie Mike]

Stop pin is the thumbstud.

or...

Stop pin is mounted in the frame.

 

[stabman]

Depends on the diameter of the stop pin.
The blade mounted stop pin will help eliminate lateral wiggle if it contacts both sides of the frame; that's a cool feature.

 

[Tony8179]

What about the stop pin that is built into the handle near the pivot like Galyean's JYD?

 

[THG]

Stop pin is the thumbstud.

or...

Stop pin is mounted in the frame.

I think it's about the same as long as the stop pin (as in the 2nd picture) runs all the way through the handle. If it's just a nipple held in place by notches in the liners, then I think those have a better chance of breaking off.

Also, if the thumb studs as in the 1st picture were separate parts later attached to the blade, then I think they would have a higher chance of breaking off. If they are integrated into the blade (they are from the same piece of steel), then they are strong.

As for which is definitely stronger than the other, I don't know.

 

[Cotherion]

Thumbstud.

1) the total area contacted is larger for the thumbstud stop pin. Area resting is curved to match the curved stop pin.

2) For the stop pin (not thumb stud version) the contact area is small and pressure is large. Deformation of the pin occurs regularly in cases of small stop pins.

 

[pwet]

If they are integrated into the blade (they are from the same piece of steel), then they are strong.

who would bother machining such a thing ? do you imagine the loss of premium steel from making integral thumb stud ?

 

[wongKI]

I'd always thought that for the integral mounted stop pin it would still be equally possible to either machine it so that the pin face is flat, or the blade contact face is rounded. Don't think I've ever seen that though.

Here's another consideration: How about a full back spacer?

 

[THG]

Thumbstud.

1) the total area contacted is larger for the thumbstud stop pin. Area resting is curved to match the curved stop pin.

2) For the stop pin (not thumb stud version) the contact area is small and pressure is large. Deformation of the pin occurs regularly in cases of small stop pins.

Well in the case of a stop pin (not stud), and assuming it goes all the way through the liners, then the liners enclose the pin, so the contact area is greater than or equal to that of the "stup studs."

who would bother machining such a thing ? do you imagine the loss of premium steel from making integral thumb stud ?

I've heard it said that one certain custom maker does this. I don't think it's something widely done, is it? Either way, if it's not integral, then I doubt it could be as strong as a stop pin (not stud).

 

[Cotherion]

Yeah THG you got a point but I was referring to the contact between blade and stop pin. Mine get's flattened after I flick open (not anymore, older/wiser/poorer ).

Effective contact area refers to the area being under load. Basically means in your example of the pins in liners, the first half of the contact surface is not contributing to load carrying capacity. Under load the pin moves away from contact (the half I mentioned). Not too important but since we are on the subject you see.

Whereas in the Stud stop, the contact area at any point/section is not small (like for stop pin to blade tang). It is theoretically stronger (still depends on the stud's design) but subject to other stuff like material type/design/dimensions/etc.

 

[Cotherion]

If one were to assume that the rough shapes/materials are the same, also generally stud stops (like for ZT30x) are thicker, then it is about the shear area.

Resolving the bending moment as being equal (distance and vector component of pivot and stop-pin/stud-stop) then the higher the shearing capacity = higher strength (OP's original question). Assuming again the Stud Stop is of thick material slotted into blade, then compared to stop pin (which normally has a screw-hole/screw) it is clear the Stud version is stronger.

 

[Daniel]

I would think that it would depend on the actual strength of the screw inside the thumb stud. Most are much smaller than a frame mounted stop pin and would not be as strong. I would also think that it would depend on the strength of the steel used in the construction of each method.

 

[Joshua J.]

You would have to be pretty silly to use a screw together stud as the stop pin.

Generally stop pins in the handle contact a flat section of blade tang, where the stud stop contacts a curved receptacle in the handle.

Regardless of strength, the stud stops have the advantage of not trapping pocket lint.
You would be surprised at how many times that's been an issue.

 

[Superfuzz]

CM,

I really like the Sharktooth Lanyard you got there...does it snag? Or are these just axamples and not your blades?

'Fuzz

 

[Cotherion]

Regardless of strength, the stud stops have the advantage of not trapping pocket lint.
You would be surprised at how many times that's been an issue.

Definite issue for me in my pocket lint infested pockets

Lockbacks, BB locks, Framelocks and Linerlocks folders all fail to open properly cause of lint.

 

[Cotherion]

I would think that it would depend on the actual strength of the screw inside the thumb stud. Most are much smaller than a frame mounted stop pin and would not be as strong. I would also think that it would depend on the strength of the steel used in the construction of each method.

You got a point. However when the stud doubles as a stop pin, then makers/designers generally beef em up considerably. At this point it must be differentiated the two different "typical thumb-stud" and the "stop-pin thumb-stud".

Wonder what's the shear capacity of different steel? Would be interesting to get some data on this. Steel experts where art thou?

 

[philwar]

In theory the stop pin would suffer less stress when it is mounted on the blade. The stress would be divided over the outer ends of the stop pin (the parts sticking out of the blade), and over the frame of the knife. The ends of the stop pin are short, limiting the leverage applied.

When the stop pin is mounted in the frame, the stress gets applies to its center, allowing for greater leverage. Think of a stick placed on two bricks, it will break in the center.

But I think it's all theory. In practice, I don't think it matters much because in both cases the pin will be able to take a lot more pressure than will ever be asked of it.

 

[wwells20]

Adding, the thumb/blade stop pin's "screw threads" will only be used to hold together the stud. This design usually has shoulders which make contact with the hole in the blade. This set-up also benefits from more surface contact area and can depending on design, can utillize the handle scale for additional support. The only way to be stronger is to press in the stud as in Kershaw. (kershaw is the first ex. that comes to mind) This would IMO be the strongest of all. One other benefit of using studs to stop the blade, it places the stud up and more out of the way. I hate to see a thumb stud placed an inch down the blade

 

[FlaMtnBkr]

I think it depends on the diameter of the stop pin and how strong it is compared to the thumb stud. If the thumb stud is screwed together I would think a solid stop pin is always going to be stronger.

If you think about it, a stop pin is rounded and sticks in a curved hole to transfer forces to the liners. Just like the rounded thumb stud and the curved section it rests against in the liners. Yes the contact area is pretty small between blade tang and stop pin. But the contact area between the blade and the thumb stud is also going to be fairly small, at least in the thumb studs that I have seen that screw together. If it is pressed in then it will increase the surface area quite a bit.

I wonder why makers don't put a curved section in the tang to wrap around the stop pin a little and increase surface area? I bet it would drastically decrease the amount of 'peening' of the stop pin that puts a flat spot in the stop pin and can increase lock engagement on a frame lock.

 

[stabman]

I wonder why makers don't put a curved section in the tang to wrap around the stop pin a little and increase surface area?

My custom CK&T karambit has that curved section.
A very nice feature.:thumbup:
My Benchmade 755 has flats to the stop pin, so the tang of the blade mates to a flat area. Also a cool design feature.

 

[pwet]

I wonder why makers don't put a curved section in the tang to wrap around the stop pin a little and increase surface area? I bet it would drastically decrease the amount of 'peening' of the stop pin that puts a flat spot in the stop pin and can increase lock engagement on a frame lock.

like that ?

this is a custom PPT made by Sasha Thiel. french custom knifemaker who makes some really incredible work. i believe that it may be a bit more complicated for an industrial to make such a refined detail. it may cost too much.

photo credit, midnight@neoczen.