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extra strong detent ball?

Discussion in 'Maintenance, Tinkering & Embellishment' started by nc527, Aug 1, 2010.

  1. nc527

    nc527

    Mar 22, 2009
    I just recieved a new sanrenmu 710. The knife is very high quality, but I have a problem with the detent ball. It is so strong, it hurts my thumb to open it. Will this get better after use?


    Also, no "hating on the sebbie clone" comments please
     
  2. The Sun

    The Sun Banned

    168
    Mar 29, 2009
    your thumb will break in with use! ;)

    it will get easier with time. there are a few things you can do to help it along, but that would probably void the warranty. also, i would rather see a detent be too strong, than too week.

    give it a little time, if you use it everyday, you won't notice it before too long.
     
  3. spyken

    spyken Gold Member Gold Member

    Apr 29, 2002
    no it wont....at least not until you've rather flattened the ball. sorry for the bad news.
     
  4. nc527

    nc527

    Mar 22, 2009
    by all means, help me along. This is a chinease made, $8 dollar knife with a 3 month warrenty

    It does have alot going for it though. 8cr13mov steel, framelock, and this strong detent.
     
  5. The Sun

    The Sun Banned

    168
    Mar 29, 2009
    see spyken's comment above ;)

    and my comment was referring to the fact, that after a while you won't notice it because you'll have a "new" thumb :)

    you can also VERY lightly countersink the detent hole to give the bearing a "ramp" of sorts. don't go very deep with it though!
     
  6. jekostas

    jekostas Banned

    72
    May 10, 2010
    Give it a few weeks of use - it may be that you've just not got quite the right angle to open the knife down. Same thing happened to me with a few SRMs. Once you get it, though, it becomes automatic.

    What worked for me is instead of pushing the knife straight up from the thumbstud, use the finger cutout as a guide for your thumb - it should be off slightly to the side.
     
  7. wongKI

    wongKI

    Jul 9, 2009
    Rather than pushing against the thumb stud itself, try sliding your thumb between stud and handle, which should ease the knife open, after which you can either flip it open with your wrist (gently does it, no need to whip-crack) or actuate it all the way with your thumb. I find it easier on some knives, although I've never tried the model of which you speak.
     
  8. spyken

    spyken Gold Member Gold Member

    Apr 29, 2002
    sanrenmus are actually quite well made. you may consider bending the lock-bar outwards just a little bit to help lessen the pressure. and grease the detent ball.
     
  9. I'd say give it some time. It may be that you just need to develop the 'muscle memory' to make opening feel more natural, as well as a nice, tough callous on your thumb.

    A very stiff detent is more a good thing than not. Especially on an 'inexpensive' knife. It'll help to keep the blade closed when it's in your pocket. Better off to leave it be. It'll probably loosen up a bit with use anyway.
     
  10. nc527

    nc527

    Mar 22, 2009
    Thanks everyone. I lubed up the detent, and tryed what wong said. Now, I start with my thumb low at the other end of the fingercutout, and slide it up against the thumbstud, flicking it out. Getting better now. I am really impressed so far with this knife. Takes a really sharp edge, no bladeplay, and 60% lockup.

    The one thing I plan to do on this knife, is round of the edge of the lockbar where I press to unlock it. They left it kinda sharp, and it kinda hurts the finger to do it alot. But hey, thats a small hinderence for an $8 knife.
     
  11. nc527

    nc527

    Mar 22, 2009
    Alright, after my "tuning" I have this knife locking up perfectly, opens and closes as smooth as buhta, and is perfectly centered when closed. Heres what I did to it.

    Took the blade out and polished the tang with 1000grit wet n dry, then 2000.
    flushed out all the crappy factory lube
    rounded off the lockbar, where you push with your thumb
    tweaked the pivot screw to get the blade centered
    lubed with mineral oil.

    side note- for some reason, it seems that on one side, the screws are allen head, and on the other side, they are torx. any1 else noticed this?
     
  12. STR

    STR Knifemaker/Moderator Moderator

    Aug 27, 2004
    Typically if the ball sticks out a bit too far and consequently falls into the hole in the blade deeper than it maybe could it will hold quite well. I've handled three of the 710 Sanrenmu folders and all three were consistent in build, thickness and the way the ball gripped. I found the Sanrenmu detents that actually work to be refreshing since most knives of this type are made and sold as gravity knives technically speaking for the most part even from so called reputable companies. I say this because I can't count on all my fingers and toes and yours too the amount of liner and frame locks I see here with ineffective detent balls that simply do not meet the legal requirement in most states. Its nice to know someone out there still knows how to do it right but in the event your model is holding a bit too much and could use a tweak what I normally do is take the knife apart and use one of the washers or one from my stock that is just a bit thinner than the height the ball sticks out. Then I surround the ball with that washer and use it as a physical block/spacer to keep from tapping the ball in so deep it no longer works at all. Basically what you will do is you use a flat end punch and a small ball peen hammer like you would use to do copper crafts or something like that. Tap the punch after placing it over the ball and the washer will stop you from taking the ball any further in than that washer thickness. So you end up with the ball bearing in the lock sticking out to the thickness of that washer.

    It may help to measure the washer or washers on the ball side of the pivot with a digital caliper so you get an idea of what those are for thickness together or by itself. If you can use one of those great but I'd at least use one to see if that is the distance the ball sticks out now or not. If say two washers together on one side was how high the ball was out there then I'd drop that down just a bit more. For example if the two washers together are .020 thickness then find a .015 washer from another knife and tap the ball in .005 more for depth and it should help a lot in how much it grabs but not knock it in there so deep that it really changes a lot. Some of the Sanrenmu folders do have two washers on one side based on the pictures I've seen of them taken apart. Also, it appears that the detent ball in the three I've are 2mm size balls. I'm just guessing but I tell you this because in the event you tweak one too deep and need it to come back out it is possible to pop that ball out of the lock by coming in from the outside with an upside down drill bit placed in your chuck and simply pressing it out of there using your drill press but of course not turned on. Just be careful to place the lock ball side down in a spot where the ball can fall into a shallow hole so you can retrieve it. A small block of wood with a small hole should be all you need to catch that ball once you pop it out of there. Hope that makes sense. I spit things out fast sometimes and have been accused of losing people in the translation. ;) I try though.

    STR
     
    Last edited: Aug 3, 2010
  13. beluga

    beluga

    Nov 17, 2001
    I didn't know what sarenmu was, so I googled it, and it kinda looks like a sebenza, doesn't it ?
     
  14. STR

    STR Knifemaker/Moderator Moderator

    Aug 27, 2004
  15. nc527

    nc527

    Mar 22, 2009
    WOW. All this is a little too complicated for me STR. Making a new washer? lol its not that bad man. You have way too much time on your hands if you did that. :D

    Also, I viewed your thread, I like the way you incorparated the clip into the knife. If they came like that from the factory, I would buy them all.
     
  16. STR

    STR Knifemaker/Moderator Moderator

    Aug 27, 2004
    I never said make a new washer. Read it again. Find a new washer from another knife is a lot different than making one. No you just need to borrow one long enough to do the job then put it back in the knife it came out of. No biggie though. If its way out there for you thats fine.

    STR
     
  17. beluga

    beluga

    Nov 17, 2001
    thx for the link str. i'm gonna have to get me one of those. only $7 ?? Damn ! :thumbup:
     
  18. knarfeng

    knarfeng senex morosus moderator Staff Member Super Mod Moderator

    Jul 30, 2006
    OK, so it's an inexpensive knife. If you are willing to risk it, you might try doing what I did to a Kershaw Salvo that had just too strong a detente. If you get it wrong, you end up with a non-locking knife or one that won't stay shut, but you don't have to take it apart and it did work for me. I did it on the Salvo because I wasn't willing to send it to be fixed and it wasn't any good to me the way it was. Little sucker actually wore a hole in my thumb from trying to open it repeatedly.

    I slipped a small screwdriver under the lock bar and bent it out away from the blade just a little so that it would exert less pressure on the ball. Just bend it a little! Not even enough to see with your eyes. If you over bend it, the detente does not engage and the blade won't stay shut. If you bend it way too much, the lock bar will no longer engage the back of the blade and you no longer have a locking knife. So be bloody careful.
     
  19. nc527

    nc527

    Mar 22, 2009
    after my tuning, Its not as bad, and my thumb is developing a callus. The clip caught on my friends pants pocket while sitting on the couch today, and bent it out when I got up, so I decided to do what I planned to do anyway, convert it to tip up carry. I broke the clip off where it seperated to the 2 prongs, ground those flush, then I had a good clip. I made a stainless backing plate to bring the thickness up, and the jb weld is drying as we speak. time will tell as to wheather it will hold. I did the same as below, but instead of the tape, I just used jb weld.


    I got my idea from this:http://forum.multitool.org/index.php?topic=12106.0
     

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