I am wondering if anybody can advise me on an epoxy that will harden to grindable hardness in a short period of time......I am using JB weld 5 min at the time and it is not hardening fast enough....I am teaching classes on knifemaking and i would like to glue up a handle before stopping for lunch and have it set hard enough to grind the handle after an hour.....if it doesn't harden good enough it ruins the belt by plugging it up......when i am making knives for myself it is not a problem as i leave them overnight to cure....or is there an alternative glue that will work.....I realize that full cure takes some time but I need to install these handles on a one day class
5 min epoxy
- Thread starter tmr
- Start date
JB Kwik Weld sets up pretty quickly. It's a bit more than 5 minutes, but I usually start shaping the handles around 30 minutes later. It will set up quicker if it's warmer, so I often put the knives in the bathroom with the bathroom heat running to help it harden up faster. Even without the heater, I can usually shape in 30 minutes, but it may be a bit gummier. The heater helps harden it more fully and in less time. I try to clean off the excess as it's curing so there is less on the handle to gum up the blade or belt. Q tips, Popsicle sticks, etc all help with this.
Devcon and JB have a Plastic Welder epoxy that was pretty quick; around a 30 minute cure time, I could work the handle in about 30 minutes, so I would epoxy before dinner and then shape the handle out after dinner. Again, some heat helps the curing speed along, and clearing the squeeze out really helps.
If you take some time to clean up the squeeze out before it cures, it will save the gumminess on the belts. Just make sure you still go slow and don't overheat the epoxy. It takes a full 24 hours to set up fully, but the JB Kwik Weld and Devcon Plastic Welder have both let me shape handles around 30 minutes after the epoxy is applied.
I do not like the JB Clear Weld 5 minute stuff. The Plastic Welder is much better.
Devcon and JB have a Plastic Welder epoxy that was pretty quick; around a 30 minute cure time, I could work the handle in about 30 minutes, so I would epoxy before dinner and then shape the handle out after dinner. Again, some heat helps the curing speed along, and clearing the squeeze out really helps.
If you take some time to clean up the squeeze out before it cures, it will save the gumminess on the belts. Just make sure you still go slow and don't overheat the epoxy. It takes a full 24 hours to set up fully, but the JB Kwik Weld and Devcon Plastic Welder have both let me shape handles around 30 minutes after the epoxy is applied.
I do not like the JB Clear Weld 5 minute stuff. The Plastic Welder is much better.
Sometimes adding hardener doesn't speed up the cure time, depending on the epoxy. If adding heat, I would not go over 100 degrees. I have had epoxy fail when I got it too warm before. Most epoxies are 150-212 max temperature, so 120 degrees is pretty close to the lower end.
MTBob
Well-Known Member
I typically place my epoxy glued handles, both 5 minute and 24 hr, under a moderate temperature heat lamp for a couple of hours. While epoxy curing time is reduced with moderately increased heat, I've also found 5 minute epoxy is gummy after an hour. I've taught a number of people how to make a knife. The epoxy drying cycle is always a scheduling issue in a teaching situation, it's preferably done at the end of the day. But, even with the best plans, it seems things change to block doing the glue-up then.
Have you thought of using CA glue. It's an imperfect solution, but it is fast! Or, how about using screw on scales - but, that leads to some additional level of complexity that may not be desirable for a first-time knife.
The other alternative is to simply set aside a number of coarse, old, throw-away belts to be used for the initial contouring.
Let us know what you decide to do.
Have you thought of using CA glue. It's an imperfect solution, but it is fast! Or, how about using screw on scales - but, that leads to some additional level of complexity that may not be desirable for a first-time knife.
The other alternative is to simply set aside a number of coarse, old, throw-away belts to be used for the initial contouring.
Let us know what you decide to do.
When I was doing Boy Scouts back in the day and was part of a living history program we helped the boys make knives. I took my traveling forge and a bunch of file steel and we forged and filed the blades then put on slab handles. In order to avoid the problems you are having we used contact cement (not really period appropriate but it was Boy Scouts. You have to know how to use contact cement but it is pretty much waterproof, heat proof, kid proof and pretty much permanent. In your application I think it could work well. It does have to air dry some before assembly but once it is together it is not going anywhere. (Full disclosure, I had annealed the blanks and taken the teeth off the section that would end up being the handle so it was ready for slabs). Good luck.
I am going to due a trial blade today using CA glue and activator and see how it works out......I can always knock the handle off and redo.....I just think that MAYBE the ca type glues get too hard and react to cold exposure by shrinking away from the metal on a full tang....roughing up the tang and the handle slabs a bit may help......Old Rock.....I would need to have the handle slabs dry fit and polished at the ricasso and make contact with the pins installed....it could work....i will also try.....i am hoping that this is a seasonal problem for me as it is still cold here in thunder bay and i think the epoxy always worked better for me in the warm weather....I am heating my shop with electric and it is always a little cooler than i would like....last months electric bill was over $500....
S obsessed
New Member
How about a methacrylate adhesive. Something like Lord 406/19 would be really fast. These are structural bonding adhesives and unlike epoxies their properties don't really change with set times. I have not used the 406/19 itself but I have used Lord 108b which is the exact same thing but in a slower setting time that is used and approved for automotive panel bonding in the same way as 3m 8115 epoxy. These both in my testing are similar in strength and toughness to g/flex but they are rated for much higher temperatures then g/flex. Sometimes the Lord one can be hard to get a hold of but if you search for methacrylate adhesive you can find some other brands. They have a shorter shelf life, like 6 months to a year than epoxies. They are kind of like urethanes in that way cause they use a catalyst instead of a hardener like epoxies. Also with epoxies you should never alter the mix ratio more than a few percent. It will always give negative properties if you do. If anything it is best to be slightly lean with the hardener so there are not excess amines in the cured product which can leave more of a blush or film on it and possibly cause interference with coatings that might go over the cured epoxy.
S obsessed
New Member
I should add that I haven't used the methacrylate adhesive for knives. Only for automotive and other fabricated assemblies. I usually use g/flex for knife scales since glue up is typically the last thing of the day so they can cure over night. This being said I am not sure how the acrylic adhesive would finish out but I think it would be worth a try and perhaps just the ticket for anyone doing something like you are. There is an automotive fast version also that may be available at a local auto body supply store but it isn't as fast as the 406/19 and not available in black. The automotive ones are more of a grey or greenish color. Also they can just be squeezed out and mixed with a stick instead of going through a bunch of mixing nozzles.