seeking advice on what went wrong

meako

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I took a treated stick tang stainless blade and nickel silver guard,knife kit making components,
epoxied them to a piece of antler and a block of Gidgee wood. Hidden tang type construction.
3 days later I pulled the wood off the tang as the epoxy had not cured .
The antler has stuck fast despite not having as much epoxy in the core as I would have liked.
The wood has cracked and split anyway because of a hidden knot I think but why is the epoxy from inside the wood still a gluey mess?
I note also that the antler did not adhere to the wood well.
all advice and thoughts welcome and appreciated.
 

Stacy E. Apelt - Bladesmith

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Sounds like you had a mix issue. Just an FYI, but the ratio is fixed, any variation will affect either curing or strength ... of both.

Mix in a shallow wide cup and stir well. DO NOT USE 5 MINUTE or similar epoxies. Use only slow cure resins. 24 hour cure is best, but 1 hour curs is the absolute minimum. Mix well for at least 60 seconds. If you use a slow cure structural resin like System Three T-88 or West System G-flex, you can pretty much guarantee a good bond.
 
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They do have a shelf life .Cheaper types ,5 or 10 min types epecially. That may prevent curing. On this forum IIRC there was a long discussion and many tests of epoxies If that still exists it might be educational.
 
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Stacy,

Are you suggesting 1 hour as a minimum because it's a hidden tang? I have been using the Bob Smith's slow cure (30 minutes it states) to good success on my full tang knives. Just curious. BTW, I hope all is well, and that it cools off down there soon, it's been brutal up here.
 
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Nope, Stacy is recommending the 1 hour min cure time for epoxy because it's about the shortest cure time that will still provide a good bond. I always use the 24 hr cure time epoxy which allows me to epoxy something today, then tomorrow it's ready to use. Epoxy cures by chemical reaction not "drying" so epoxy on a hidden tang would tend to cure faster because epoxy curing reaction is an exothermic chemical reaction which means it's creating heat causing a faster cure. The epoxy being inside the hidden tang would tend to hold the heat inside causing a faster cure.

Oh, if the epoxy is still soft - you didn't get any harder mixed with resin.

Ken
 

Darrin Sanders

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Just a little tip. Leave the leftover epoxy in the mixing cup and check it to see if it got hard before you finish the knife. That way you have no doubt about whether it was mixed properly.
 
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I have wondered about cure times for epoxies. I'm not sure how the cure times could really be comparing apples to apples, especially with the slower curing types. For instance, the Bob Smith I referenced is called Slow Cure 30 minute. However I think that is the working time, as the Full cure time is listed as 6-8 hours. Working time seems kind of subjective and can vary with temperature and the application (stick tangs contain the heat). Either way, I'm confident in it.
 
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Yep, Kevin is correct, the "working time" is MUCH different - and shorter time - than the "cure time" When we talk about a slow cure or 24 hr epoxy we're talking about the cure time. If you keep the epoxy spread in a thin layer when using the working time will be extended vs having the epoxy sitting in a cut with a thick layer due to the extra heat created when in thick layer.

Yep, I've always kept the excess epoxy laying around to watch to have a good idea the mixing was good.

Ken H>
 

AVigil

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Spend 1 minute stirring and mixing your epoxy until it is completely mixed.
 

Stacy E. Apelt - Bladesmith

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This is just an approximate:
5 minute epoxy has about 60-100 seconds work time before it starts to react and gel. It is foolish to try and put a knife together in that time.
30 minute epoxy has about 5-7 minutes pot life. This is OK for some single knife stick tang jobs, but still will not be as strong as a slower cure resin.
1 hour epoxy has about 10 minutes work time. This is sufficient for general knife work.
2 hour has about 15 - 20 minutes. Even better.
24 hour has about 25- 45 minutes pot life. By far the best choice for permanent and high quality joints and assembly.

To extend pot life have the resin in a wide container so it has only a shallow depth. This slows the exothermic reaction. Setting the pan on a bed of ice isn't a good idea, as it may cause condensation to form on the resin. Setting the mix pot in a bowl of cool water is OK in hot weather.

Keep the mix pot sitting by the knives after glue up and check the pot to see how the cure is going ( not the knife). Once it gels, there should be no movement or adjustment made on the knife. When it is solid, but sticky, you can safely wipe the blade down for the last time, and then let it sit undisturbed for at least 12 hours. 24 is even better. When fully cured the resin in the pot should be like solid plastic.

If something goes wrong in assembly, just heat the whole knife up to about 200-250F and the handle will pull off. Clean everything up and repeat with slower cure resin. You can stick the whole knife in the oven or just heat the blade and handle with a heat gun ( best way).
 
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Thanks Stacy. I think the stuff I'm using would actually fall into your one hour definition. I get around ten minutes of work time at around 70 degrees.
 

meako

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Sounds like you had a mix issue. Just an FYI, but the ratio is fixed, any variation will affect either curing or strength ... of both.

Mix in a shallow wide cup and stir well. DO NOT USE 5 MINUTE or similar epoxies. Use only slow cure resins. 24 hour cure is best, but 1 hour curs is the absolute minimum. Mix well for at least 60 seconds. If you use a slow cure structural resin like System Three T-88 or West System G-flex, you can pretty much guarantee a good bond.

I think you nailed it Stacey.
I used 5 min epoxy - nb it came in a tube that premixes as as you squeeze it out.
I mixed the 2 parts together with a match as suggested.
What intrigues me is the antler is stuck fast to the metal which is good -but the the exact same glue in the gidgee hole didnt even set.
Thanks for all the advice and tips.
cheers.
Next attempt will be 24hr cure 2pack super strength.
 
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Mixing the epoxy very well with the correct ratio of resin to hardened is important. But surface prep is also vital. Clean all parts well. Cleaning is important with oily woods like Gidgee which can make adhesion a challenge. Make sure mating surfaces are FLAT. It's not enough that each individual component has flat surfaces. In addition, the fitment of all those surfaces together must have zero gaps. The mating surfaces (and pins) should be roughed up with a low grit abrasive like 80 grit paper. This will give the epoxy plenty of surface area and purchase. And when the epoxy is applied and parts assembled, do not clamp too hard or you will get a glue starved joint.
 

meako

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Well it all turned out OK in the end.
I used longer setting epoxy,a piece of old leather belt and a piece of scrap timber out of the firewood bin at a local joinery-could be Spotted gum but not sure. It certainly had none of the "issues" that my $20dollar piece of Gidgee had:grumpy:
Its all stuck fast and although the blade is a tad small for the size of the handle it rides well in hand and is comfortable.Quite happy with the result as it was a first attempt with the leather bit.
Cheers all for the good info.
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20160906_144100_zpsjt62citm.jpg
 

Stacy E. Apelt - Bladesmith

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I missed one thing in the OP. The wood that had the problem was gidgee. Gidgee gets really HOT when grinding, especially if you don't have VS. That could easily heat the wood up above 200F and make the glue joint fail. The softer wood on the new handle would not have had that problem.


Gidgee is a beautiful wood, but not the easiest to shape and finish.
 

meako

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Thanks Stacey.
I was using hand tools mainly a rasp to do the shaping -I also feel there may not have been enough glue in there. Alls well that ends well.
cheers.
 
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