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Slipjoint bearings?
- Thread starter Ken H>
- Start date
- Joined
- Dec 11, 2000
- Messages
- 1,115
Doesn't make sense to. Slip joints have a spring that is always applying a load to the blade. Well finished and relieved liners of brass or bronze, or washers of a low friction material, offer sufficiently smooth operation that the drag of the back spring is the main thing that one feels. Diminishing returns, bearings would be smoother, but you wouldn't notice the difference. They wouldn't make the difference they do in flipper knives.
Like putting carbon/ceramic brakes on your mom's mini-van...the limiting factor in how fast the van stops isn't going to be the pads/discs, but the tires and your mom's right foot!
The real trick with modern slip joints is shaping the tang and how the back spring interacts with it. The Viper Key is a good example. Very modern, M390, titanium, carbon fiber, bronze washers, very cool looking...but the tang is square, about as modern as a Conestoga wagon, and it is a right pain to open. Real nail buster. Contrast with Boker Plus Slick, or the old Enzo PK70, or the Spyderco PITS all of which have tangs that allow easier opening than closing, so they don't need such a strong spring. Intelligent design over brute strength.
Like putting carbon/ceramic brakes on your mom's mini-van...the limiting factor in how fast the van stops isn't going to be the pads/discs, but the tires and your mom's right foot!
The real trick with modern slip joints is shaping the tang and how the back spring interacts with it. The Viper Key is a good example. Very modern, M390, titanium, carbon fiber, bronze washers, very cool looking...but the tang is square, about as modern as a Conestoga wagon, and it is a right pain to open. Real nail buster. Contrast with Boker Plus Slick, or the old Enzo PK70, or the Spyderco PITS all of which have tangs that allow easier opening than closing, so they don't need such a strong spring. Intelligent design over brute strength.
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Thank you for the response - well explained and makes perfect sense. I've only made slipjoints, and looked at the bearings in liner locks with envy thinking they might make things better on a slipjoint. When the tang is designed correctly (corners with a very slight radius) opening/closing is smooth anyway.
Thank you for taking the time for a good explanation.
Ken H>
Thank you for taking the time for a good explanation.
Ken H>
- Joined
- Dec 11, 2000
- Messages
- 1,115
All you make is slipjoints? Oh man...talk about me telling grandma how to suck eggs! 
If you are set up for the work already, you could give it a try! If you have reduced friction enough with the spring/tang, you might be able to detect a difference between washers and bearings. The other thing that might work better with bearings is if you were going big. Bigger washers stabilize the blade, less chance of lateral wobble, but they also increase friction. I think that Sebenzas used perforated washers to reduce contact and trap grease, but a bearing might be able to act at a bigger diameter without paying the friction price of a bigger washer.
The other thing is market forces. Lock knives is where the US market has been for years, ever faster opening folders. Fast as opposed to merely smooth. Bearings seem to go in flippers and assisted knives so that a quick kick will swing them open. There hasn't been the interest and therefore money in non-locking knives, so they have tended to stay very traditional looking. No real pressure to innovate. Its only been the last few years that laws have tightened enough around the world so that there is enough critical mass of customer interest in modern, high tech non-locking knives to get manufactures (and more makers?) looking at the options available.
Even so, most are still going for the gents EDC size and shape. The Spyderco PITS is a different beast because it was designed as a UK legal hunting knife. Mike Read wanted a knife he could carry for shooting (cleaning small game) that he didn't have to worry about legality if he carried it in town or stopped at the shops. (No need to comment on that situation folks
) Something of a similar radically different style might benefit from bearings. Not for speed, but for size and stability.
All the best
Chris
If you are set up for the work already, you could give it a try! If you have reduced friction enough with the spring/tang, you might be able to detect a difference between washers and bearings. The other thing that might work better with bearings is if you were going big. Bigger washers stabilize the blade, less chance of lateral wobble, but they also increase friction. I think that Sebenzas used perforated washers to reduce contact and trap grease, but a bearing might be able to act at a bigger diameter without paying the friction price of a bigger washer.
The other thing is market forces. Lock knives is where the US market has been for years, ever faster opening folders. Fast as opposed to merely smooth. Bearings seem to go in flippers and assisted knives so that a quick kick will swing them open. There hasn't been the interest and therefore money in non-locking knives, so they have tended to stay very traditional looking. No real pressure to innovate. Its only been the last few years that laws have tightened enough around the world so that there is enough critical mass of customer interest in modern, high tech non-locking knives to get manufactures (and more makers?) looking at the options available.
Even so, most are still going for the gents EDC size and shape. The Spyderco PITS is a different beast because it was designed as a UK legal hunting knife. Mike Read wanted a knife he could carry for shooting (cleaning small game) that he didn't have to worry about legality if he carried it in town or stopped at the shops. (No need to comment on that situation folks
) Something of a similar radically different style might benefit from bearings. Not for speed, but for size and stability. All the best
Chris
Thank you for your responses - they all make good sense. I go for a softer backspring, the ladies don't like breaking nails pulling open {g}
That could well be a big driving force. I'm no expert by any means. I've made 15 or 20 slipjoints, sold 1/2 dozen perhaps with rest given to family 'n friends as gifts. I've been happy with the opening smoothness and "walk 'n talk" action. Here's one I've made. San Mai blade with 416SS cladding & 1095 core, Mammoth ivory scales. Liners milled from 416SS with integral bolsters. I had a delam on the billet and got that much good for a folder blade.
- Joined
- Apr 20, 2005
- Messages
- 2,356
About 10 ish years ago I was making slipjoints "full time" and after making a couple hundred of them I see no reason
to try even doing the bushing thing. As has been said above if the spring tension is good and the slight corner radius good
the girls won't break their nails.
Ken.
to try even doing the bushing thing. As has been said above if the spring tension is good and the slight corner radius good
the girls won't break their nails.
Ken.
- Joined
- Dec 23, 2018
- Messages
- 43
Fascinating thread, thank you all for the education.
I’m in a “no lock-back” locale, and wish I could afford a custom, medium to heavy weight slip joint with a robust 3.9” blade, a swing guard, and a look and name that doesn’t scream “tactical death/dealer!”
As it is, the look of my Boker Plus Chad Los Banos scares my wife, and now the tip is bent.
I’m in a “no lock-back” locale, and wish I could afford a custom, medium to heavy weight slip joint with a robust 3.9” blade, a swing guard, and a look and name that doesn’t scream “tactical death/dealer!”
As it is, the look of my Boker Plus Chad Los Banos scares my wife, and now the tip is bent.
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- Joined
- Apr 3, 2009
- Messages
- 3,283
The bushing in a slip joint isn't necessarily designed in there to make the knife smoother or easier to open. Its main function if done correctly is to reduce wear to the pivot pin and keep it hidden over time after blending it into the bolster material.