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Corby bolts + epoxy ?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Travis_Wright, Jul 3, 2019.

  1. Travis_Wright

    Travis_Wright

    15
    Jan 27, 2019
    I'm having a terrible time with using epoxy and pins on my knife handles. I keep getting separation between the full tang and the wooden scales after a while. I'm curious to see if anyone has switched to using corby bolts vs. pins to help with this issue or will this even be helped with corbys.
     
  2. weo

    weo KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 21, 2014
    All I use is corbys. Never had a problem and everything I've heard or read says that corbys are the solution to that issue.
     
    Ken H> likes this.
  3. Matt Rochester

    Matt Rochester

    Nov 28, 2014
    It will help but there are other common issues. On issue I see with pins are that you ha e to clamp them. Too tight and you can press out too much epoxy and you have a glue starved joint that can fail. Good quality, slow cure epoxy is a must in my opinion. Unless you are using mosaic pins or some type of carbon fiber/g10 then I don’t know why anyone wouldn’t use Corby bolts. So, get everything flat, clean with a no residue cleaner, apply good epoxy, and just sung up the Corby bolts. This will last a long long time.
     
    Robert Erickson, Ken H> and DanF like this.
  4. seanj

    seanj

    209
    Mar 1, 2010
    Be certain that both your tang and your handle material is absolutely flat. Even if it looks flat to you it may not be. That was my biggest problem when I first started.

    I use a small granite surface table to check for flatness. I also will usually sand both the tang and the handle material on the surface plate as a final preparation before assembly. Do a dry fit and check. If everything looks good then use a good epoxy and don't over clamp. When I use Corby bolts I don't even use clamps. I simply tighten the Corby bolts up until I begin to just see epoxy around the edges. If you feel it's necessary you can tighten them up a bit more after the epoxy has set for a bit.
     
  5. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    As the others have said, Corby bolts are the strongest and most secure handle construction. No gaps, no lift, no failures.

    One trick to assure a strong handle construction is to grind out some metal from the center of the tang, leaving a flat perimeter that will seat flush with the handle scales. The epoxy pools in the recess and makes a strong bond. Altrenatively, drill lots of holes through the tang.
     
    Brian77, robwil, Ken H> and 1 other person like this.
  6. Bill DeShivs

    Bill DeShivs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 6, 2000
    Or, if you peen your pins, you won't have any problem.
    Knives were made for hundreds of years before epoxy was invented, with peened pins.
     
    DanF, allenkey, AVigil and 2 others like this.
  7. john april

    john april KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Feb 27, 2006
    in my experience, if wood is pulling away, twisting or lifting it was too wet or too dry when the scales were applied and shaped. can you post a photo of the problem ? does it happen when you use micarta ?
     
    milkbaby and deepobs like this.
  8. butcher_block

    butcher_block KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 6, 2004
    i use pins but set up like stacy dishing the back of the scale and the tang to make sure good epoxy bond. why i use pins not corbies is if some one ends up with a dishwasher knife and scales pop often times i can save the wood by sanding the pins a hair driving them out then resurface the scale back . epoxy pin and refinish good as new jsut slightly smaller
     
    Brian77 and AVigil like this.
  9. Cushing H.

    Cushing H. Gold Member Gold Member

    432
    Jun 3, 2019
    I can try to add something here ... i have done a lot of adhesion work on difficult to bond materials in medical device design...

    Agreed with what has been said before (dry stock to avoid warpage - critical; dont squeeze out epoxy - should not really be all that important; flat stock - important but critical for appearance; clean with alcohol or acetone - critical; clamp or keep secure until cured - critical).

    I would add the following: flat does NOT mean “smooth”. A roughened surface(s) will absolutely help, and might well end up being THE critical factor in retaining adhesion over time. This, i believe, is especially true when using any plastic or resin containing materials (including stabilized wood), and my guess is also with any highly resinous woods (which of course are the most attractive ones ). So before bonding i would attack those mating surfaces with surprisingly rough sandpaper - like 100 or even 60 grit (a smooth surface is actually really bad for several reasons). Doing this will help retain adhesion over time, and should all but cure the “epoxy squeeze out” problem some have noted (a thinner glue layer should actually be stronger and last longer)

    If you would like, i can give a somewhat longer explanation on the “why” of the above, but am not sure if you want that (and i am on my ipad right now ... and my fingers just do not work well with this keypad (or the other way around....)
     
    Bamph, Alex Topfer, robwil and 2 others like this.
  10. Natlek

    Natlek

    Jun 9, 2015
    For hidden tang I will use epoxy .For full tang and scale I will use epoxy but I will peen pins . Epoxy do not hold very much on steel and that is fact .Even with rough prepared surface.This tang was ground with angle grinder ...still no sign of epoxy there after separation . When you flex thin blade you will hear sound how scale peel in in front of the first pin....You can try this ...glue some wood /scale/ on steel without pins and try to separate ....you will be surprised how easy it will be to separate them .Pins are what hold all in the place . I found that polyurethane sealant is better for gluing scale on steel if pin was not secured .Wood is another story ...this handle on picture is from two part....glued part is stronger then wood

    [​IMG]
     
  11. Cushing H.

    Cushing H. Gold Member Gold Member

    432
    Jun 3, 2019
    You can certainly make almost any joint fail. Flexure from side is the absolute worse (concentrates stresses on one very small edge .. then the rest of the thing just zips apart)
     
  12. Travis_Wright

    Travis_Wright

    15
    Jan 27, 2019
    I already popped the scales off the handle so no pics. I think it was a combination of a few things with moisture being the biggest problem but I'm still not convinced that Corbys aren't the way to go in the future. Cleaning up epoxy around clamps is for the birds.
     
    john april likes this.
  13. Cushing H.

    Cushing H. Gold Member Gold Member

    432
    Jun 3, 2019
    I think Corbys are cool (I have several sets and plan to use them) - however, my concern is that if you have a bad joint, the Corbys might keep the think from falling apart ... but they wont stop a fissure from developing between the tang and handle ... which then becomes a grime/dirt haven, ultimately having an impact on the appearance of the knife (also, many argue that getting the dimensions / depth of the holes correct for Corbys is harder than just drilling holes for pins. Plus, for small knives Corbys are just too big.... Better in the long run to understand how to operate without them (corbys)????
     
    allenkey likes this.
  14. allenkey

    allenkey Gold Member Gold Member

    101
    May 19, 2018
    I really love your no bull/ no frills advice. It's so refreshing to read and just reminds me to keep it simple. Respect, sir.
     
    Brian77 and Bill DeShivs like this.
  15. allenkey

    allenkey Gold Member Gold Member

    101
    May 19, 2018
    Edit: nevermind
     
    Last edited: Jul 4, 2019
  16. Hengelo_77

    Hengelo_77 Basic Member Basic Member

    Mar 2, 2006
    Crushing H, please do explain more in depth. I find this very interesting.

    I usualy rough up a tang with cut off disks in a Foredom, have extra holes and hollow out scales.
     
  17. milkbaby

    milkbaby

    579
    Aug 1, 2016
    Wut John says above... If your wood isn't dry then even if you use mechanical fasteners/peening, it could still pull up and/or split. Even stabilized wood I'm paranoid and like to have it equilibrate a year or two in my shop before using, and I've heard one maker even say that he waits five years after receiving the wood back from the stabilizer! :eek:
     
    john april likes this.
  18. weo

    weo KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 21, 2014
    How small a knife are we talking about?
    They've got 1/8" corbys.
    [​IMG]
     
    Last edited: Jul 4, 2019
  19. Cushing H.

    Cushing H. Gold Member Gold Member

    432
    Jun 3, 2019
    Huh, my mistake. Mine are 1/4 inch ... but i bought them so many years ago i guess i forgot (or never knew) they come in smaller sizes. Good to know - thank you
     
  20. weo

    weo KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 21, 2014
    That's what I thought and why I posted. I wasn't questioning you aesthetic tastes.
     
    Brian77 likes this.

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