Does the spring have to be flush?

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    • Does the spring have to be flush?

      I cant imagine anyone not appreciating a well made traditional slipjoint and I am no different, I think they look fantastic and though I only own one (Case Stockman) and have never made one, I always look at the ones posted with admiration - one day!

      I have made sketches of several designs but have never got as far as making one. The reason being that I always get stuck with the spring design - why does it have to be flush?

      It makes sense to have the spring nice and flush in the open position but why when it is closed?

      If you could have the spring sitting a mm or so low in the closed position, the knife will be easier to open and could be made to close in a safer more controllable manner. Both without sacrificing security in the open position.

      Would this still be a traditional slipjoint?
    • Because it's seen as a mark of quality, skill and attention to detail by the maker.

      If a maker says it's not flush for the purposes of easier opening, then it could be seen (by some cynical folk) to be a retrospective justification for the maker's eff-up. But if it's coming from you, I think your customers would know you'd done it intentionally!

      You could always just shield the back spring under another layer of something (a bit like what I think Vagnino did with his Zip Slip line)?
    • "Would this still be a traditional slipjoint? "

      By the masses probably not ...but for most of the guys who are in "deep" with this genre of loveliness ....I would hope they see that thru the history of slipjoint's there have been loads of variations on similar patterns and to deni another variation would be just wrong ...in my opinion anyway

      I'm with Hugh ,as to the "why" it's done and if I'm honest I do like to see it myself ....A little like the flush in all 3 positions kick ,is it neccesry ,nope ,is it a show of talent yes ....Would it stop me from buying a knife because it wasnt flush in the half stop ,nope :)

      Can I ask why it would be a safer lock if it was sunken in the closed position ,...just trying to get me head round it

      Though ...Again like Hugh said ,If it was to come from your workshop ....I don't think you'd have trouble getting orders ;) :thumbsup:

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    • @mason knives will give you a good answer I'm sure

      For me, it has to be flush, both open and closed.

      Open - so it doesn't get in the way as it will have sharpish edges

      Closed - so the backspring (the spine) is protected and doesn't get knocked about, so possibly impeding its smooth action
      ..





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    • pieinthesky wrote:



      If you could have the spring sitting a mm or so low in the closed position, the knife will be easier to open and could be made to close in a safer more controllable manner. Both without sacrificing security in the open position.
      Could you please elaborate as to why the blade would be easier to open if the spring is lower than the frame. The shape and thickness of the spring really determines the pull, not the shape of the tang so much.
      The spring should rise by half its width on operation, this ensures a smooth pull and does not put undue strain on the spring.
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    • I'm with the flush open and closed brigade I am afraid. I cannot say with any authority whether your idea would be an improvement or not, so I won't attempt to. I sure would love to see a traditional pattern folder from your hands though. Picture a no.8 gents folder but with a PITS back spring and solid Ti scales. No pocket clip or holes in the handle ala the Mk3. A traditional folder with a modern slant, they would fly out.
    • mason knives wrote:

      pieinthesky wrote:

      If you could have the spring sitting a mm or so low in the closed position, the knife will be easier to open and could be made to close in a safer more controllable manner. Both without sacrificing security in the open position.
      Could you please elaborate as to why the blade would be easier to open if the spring is lower than the frame. The shape and thickness of the spring really determines the pull, not the shape of the tang so much.The spring should rise by half its width on operation, this ensures a smooth pull and does not put undue strain on the spring.
      When I first designed the PITS folder the spring bar was lower when the knife was closed than when open. The reason being that the spring force needed to hold the blade closed didn't need to be as much as to hold it open. Another advantage of this arrangement was that the effort needed to start the blade opening was much reduced. Obviously when the spring is lower it exerts less pressure on the tang and hence generates less friction.

      I would expect exactly the same to apply to a slipjoint. Maybe the benefit is not significant - until I try it I will not know for sure.

      If I built a slipjoint I would want the blade to drop into the closed position similar to the way lockers do - rather than snapping shut like a trap. It may be possible to do this and keep the spring flush but, having the spring lower in the closed position and carefully shaping the tang would definitely work.

      Hope that makes sense.

      I guess I am putting function before form
    • Putting a slight radius between the half stop & closed position on the tang should weaken the closing "snap" & make it easier to pull open as well.
      As long as the spring still exerts some force on the correct side of the pivot the half stop & close will still work just a lot weaker.

      Or don't have a half stop just a semi-circular tang with a open & closed stop, no snap then.

      To have the spring flush in all positions it seems like there is only so much can be tweeked with tang shape, it' s a bit of a compromise.

      If you want different spring levels, why does the spring have to show at all? A Douk-douks spring is hidden.
      ;) OK it could be done a bit smarter.

      I'm certainly no expert & you probably know all this already.........
      :)

      The post was edited 2 times, last by Navaja ().

    • Firstly excuse the dodgy drawing but computer stuff is way out of my abilities.

      I've tried to draw an exaggerated example of what I think should work as an easy open & close with no snap, while keeping the spring flush open/closed.





      A relitavely weak shaped spring uses the angle of A to gain an advantage in keeping it open. In my drawing the angle is too steep & wouldn't close but playing with A & B or making them much rounder should make it more difficult to close compared to a flat spring.
      It should open easy due to the contact C being close to the pivot, then slowly ramp up as opened. A half stop could be cut but probably not needed.

      OK folks, pick it to bits :) what do I not see.
    • Remember the spring also acts against the blade as a stop to support when open and cutting. If the spring is made too weak pressure is applied to the blade the spring will fail catastrophically...... Not a good thing.....

      The suggestion above has the potential for the blade to slide under the spring. A stop pin could be incorporated to prevent this but then we are moving further away from the "simple" spring back or slipjoint.......

      ......And yes, everything must be flush.
    • Polardiver wrote:

      Remember the spring also acts against the blade as a stop to support when open and cutting. If the spring is made too weak pressure is applied to the blade the spring will fail catastrophically....
      The end of the spring buts up against the blade as normal, excuse my drawing it's the gist of the shape, not accurate. I don't mean the spring should be exceptionally weak, just relative to an easy opening spring with the shaped end making a sort of detent to help keep it open.

      Chui wrote:

      @Navaja - think these kind of things are great to explore, good for you :thumbup:

      Perhaps, make those shapes in simple perspex and see how they work........you could be onto something, man :)
      Like just about anything the easiest way to know if it'll work is just to look around & see if it's been done :)

      All my slipjoints have a squarish tangs, just curious if anyone has another shape?

      Pivots, tangs & springs are really simple...... with about a million ways of doing them!