PSI to open a folder

[Tommy W]

This is my first post,
Has anyone done any research on the topic of how much force it takes to open a folder. I saw a video awhile back of a guy measuring the poundage it takes to open slipjoints, If I remember right he just attached a small scale to a blade pulled it open and took note of the psi. from there he could sand down the spring to whatever he thought was a good pull weight. I can not find the video anymore. I am new to making folders ( I have made only one folder )

 

[KenH]

I'd not thought of using a scale to measure - I might try that. Have to make a clamp to attach to blade at the nail nick and check for opening pressure. That's just "P" (pounds), NOT PSI (Pounds per Square Inch) you're looking for.

 

[TimGinMN]

If you break your thumbnail opening it... it's too much. (Kind of a trial and error process that takes a long time since you have to wait for the nail to grow back after each test...)

 

[jaxxas]

If you use a thumb stud you could easily attach a fish scale to determine the how many pounds it requires to open.

 

[Drew Riley]

Even if you know the exact "weight" of the pull, it's such a subjective thing from one knife (and user) to the next. I guess it's not a bad idea for consistency between models, but even then there will be changes as the knife breaks in. Size of the knife makes a big difference, as does the geometry around the nail nick, it's location away from the pivot, etc....

 

[KenH]

I rigged up a test setup for this. A fairly easy opening slipjoint was around 1.5 lbs pull at nail nick. A heavier pull slipjoint was 2.5 lb at nail nick. The actual lb pull would change over time, but I wouldn't expect it to be but an ounce or 3 at most. The attachment point must be at center of nail nick. The lb pull from tip of blade has little to do with it, if the nick is close to tip the nick value will be closer to tip lb pull. If the nick is located closer to pivot point the nick value will be a good bit higher than tip value.

Different folks want different lb pull to open blade, some folks like a heavy pull so the blade really "snaps" in each position. Other folks (especially ladies like my wife and granddaughters) prefer a lighter softer pull so there's no danger of precious fingernail damage.

 

[Tommy W]

I rigged up a test setup for this. A fairly easy opening slipjoint was around 1.5 lbs pull at nail nick. A heavier pull slipjoint was 2.5 lb at nail nick. The actual lb pull would change over time, but I wouldn't expect it to be but an ounce or 3 at most. The attachment point must be at center of nail nick. The lb pull from tip of blade has little to do with it, if the nick is close to tip the nick value will be closer to tip lb pull. If the nick is located closer to pivot point the nick value will be a good bit higher than tip value.

Different folks want different lb pull to open blade, some folks like a heavy pull so the blade really "snaps" in each position. Other folks (especially ladies like my wife and granddaughters) prefer a lighter softer pull so there's no danger of precious fingernail damage.

Thanks good info,Tommy

 

[Calvin Robinson]

If you break your thumbnail opening it... it's too much. (Kind of a trial and error process that takes a long time since you have to wait for the nail to grow back after each test...)