epoxy handle falure

T

thatsaknife

Joined
Mar 27, 2015
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247
hello knife people:)

Had my purpleheart handles pop away from knife while shaping them today.
wood came away from metal.The metal had no epoxy all was stuck to wood
Used 2 tonne epoxy from hardware devcon?
set overnight in clamps. pretty tight.
surface prep was sandpaper.
Used BRAKE CLEANER to clean surfaces. I usually clean surfaces with PVC pipe cleaner.

Anyway they came off clean with a little wiggle.
I resanded surface cleaned with PVC Pipe cleaner and tried again with an old set of epoxy.
Clamped tight. Maybe I clamped too tight?
Thanks
 
I would suggest making sure your surfaces are roughed up. The cleaner itself might be good for brakes and pvc but could be leaving a film. I would finish cleaning them with denatured alcohol as that will evaporate without residue.

Did you use pins as well as epoxy?
 
Some pictures may help. What does the epoxy have to grab on to? Does your tang have holes or dimples? Did you use any mechanical fasteners, or just epoxy? I just wipe my tangs down with a clean cloth and denatured alcohol. I'm not sure if brake cleaner will work also.
 
I am using the Devcon stuff myself, and am liking it well enough. Make sure the tang is roughed up...not smooth. I always have weight reduction holes in the tang as well to act as areas to form an epoxy bridge. Also the underside of my handles (wood, G10, etc) are roughed up, and using the dremel, I will carve a few gouges for additional areas for the epoxy to set into. Also, the pin holes are chamfered on the tang and handles as well. Lastly, Acetone followed by Windex. 4 clamps 24 hour set.
 
Yes I made stainless pins from a 1/4inch hex bolt. Usually use brass. I use the pipe cleaner as I figured if its good for pipe cement cleaning it should be good for epoxy. Maybe I am wrong. It has worked well on 3 other knives so I thought that maybe the Brake cleaner was the variable that caused the failure? I also tighten the clamps fairly tight. I read that some people use only spring clamp pressure
 
In my opinion, hardware store epoxy has no place on a knife. There are several good epoxies available, but none are consumer grade. I use the hardware store Devcon and Loctite epoxy for fixturing etc where the fast set is helpful, but never on a knife.

Also important is very good surface prep, and very through mixing of the epoxy.
 
I consider epoxy to be mostly a gap filler/sealant, and rely on mechanical fasteners for strength. Peened pins or Corby's..........flared tubes......and for sure some holes thru the tang for the epoxy to fill.
Darcy:)
 
set overnight in clamps. pretty tight.
Click to expand...

It is possible to squeeze all of the epoxy out with clamps. I use rubber bands after squeezing the scales by hand. Concave tangs with a few holes to bridge the epoxy and no clamps should help.
 
Too tight clamping could be a problem, you starve the joint. I typically only use spring clamps and blue masking tape, learned after making the same mistake a few times. Also I'd stick with acetone and denatured alcohol to clean blade and prep handles, even rubbing alcohol can leave a film.
 
lessismore said:
It is possible to squeeze all of the epoxy out with clamps. I use rubber bands after squeezing the scales by hand. Concave tangs with a few holes to bridge the epoxy and no clamps should help.
Click to expand...

As I stated in my post, if you have weight reduction holes, or holes specifically milled in for epoxy to migrate into....it will not be possible to squeeze ALL the epoxy out with clamps.
 
samuraistuart said:
As I stated in my post, if you have weight reduction holes, or holes specifically milled in for epoxy to migrate into....it will not be possible to squeeze ALL the epoxy out with clamps.
Click to expand...

Agreed, but until we know if there were any holes drilled to "bridge", do you think it's possible to have it clamped so tight that only a very thin layer remained? I can see that popping off like nothing.
 
I feel the same. I use devcon and Corby's.
DEllis said:
I consider epoxy to be mostly a gap filler/sealant, and rely on mechanical fasteners for strength. Peened pins or Corby's..........flared tubes......and for sure some holes thru the tang for the epoxy to fill.
Darcy:)
Click to expand...
 
All the above, plus:
-Brake cleaner is something you should never have in a shop where there's heat applied to what you've cleaned. It's well documented that when heated it can convert to EXTREMELY toxic compounds. Look it up. Not toxic when dry, leaves no hazardous residue, but I'd about as soon have uranium in my shop.
-Heat. It's possible to generate enough heat during shaping purpleheart on belt sanders that the epoxy would be compromised. (The wierd thing about PHeart is that it gets prettier when you heat it, it restores the purple)

I used Devcon when I started out, and had some failures despite good application practice. There are MUCH better epoxies out there...Nathan said it best.
 
I'm surprised by the number of knifemakers using Devcon Epoxy. It has poor shelf life and about a 5 year bond life. G/flex and Acraglas are much better epoxies.

When I spoke to West Systems they said maximum bond strength was at .007" and thicker. Make sure to leave space for the epoxy to do its job.

Chuck
 
I have to agree that G/flex is much better bond accompanied by mechanical fasteners. I have used enough brake fluid on brakes to know there is an oily residue to help fend off oxidation/rust you can feel the slick surface once it has mostly evaporated. A good rough sanding followed by either acetone or denatured alcohol (be sure to wear nitrile gloves so you don't leave oily finger prints) will improve your retention.
 
Nathan the Machinist said:
In my opinion, hardware store epoxy has no place on a knife.
Click to expand...


Agreed.

I'm a fan of having redundant methods of fastening (pins, bolts, adhesives, etc. used in combination), but at the end of the day ANY ONE should be enough. The others are simply insurance. Pick each type properly and you're good to go! Despite one type having the balls to do the job, you should always use two.

Nathan, have I told you how cool you are lately, bud? Cuz you are, man, you are... :D
 
Alpha Knife Supply said:
I'm surprised by the number of knifemakers using Devcon Epoxy. It has poor shelf life and about a 5 year bond life. G/flex and Acraglas are much better epoxies.

When I spoke to West Systems they said maximum bond strength was at .007" and thicker. Make sure to leave space for the epoxy to do its job.

Chuck
Click to expand...

".....set overnight in clamps. pretty tight....."

Chuck had all the answers. If you clamp flat sanded wood and metal surfaces together tightly, the epoxy will enter the wood a slight bit and squeeze out of the joint. This is called a glue starved joint, and has almost no strength. Strong and long life resins and proper gap or void to allow for enough resin to make a joint are how to avoid the problem.

I relieve the tang and often the handle scales about .010" ( each) leaving a .10 perimeter that is still flat. This insures a perfect fit when clamped.
 
I think i am clamping too tight and squeezing out the glue. I realize that glue doea not soak into metal like wood. Sanding the metal more also helped. Thanks its really nitpicking however as the pins will ensure the knife wont fall apart. Even when the glue line failed the handle wasn't going anyware
 
Please try Loctite Speedbonder. The only way to break the bond is with torch. I have put a scale and liner bonded with this into a container of lacquer thinner, acetone and naptha for a week and nothing affects this stuff. I have never had a failure.
 
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