Epoxy question

[Kms399]

Hi I'm new here just joined. My son loves making handles for knives and we've had some success but the knife I'm making for my wife caused me some issues. I shaped the handle, epoxied and set the pins. Next day while shaping I noticed the handle had started separating from the tang. Question is what epoxy is best for attaching scales? I'm using Bob Smith epoxy. I tried gently separating the scale from the blade and using the air compressor to drive more epoxy between. Hopefully that works.

 

[Hengelo_77]

Did you let the epoxy set somwhere cold?
I made that mistake once.
Epoxy needs warmth when setting. The warmer the better.

 

[Kms399]

Did you let the epoxy set somwhere cold?
I made that mistake once.
Epoxy needs warmth when setting. The wormer the better.

My shop is heated but it was only around 50 over night

 

[Hengelo_77]

That is to cold.
I let epoxy set in the bathroom with the heating on max.

Heating epoxy while mixing and aplying also works better

 

[john april]

sounds like the handle material curled. what is it? the best epoxy in the world will not hold if that happens. how were the surfaces prepared before the glue up?

 

[Kms399]

sounds like the handle material curled. what is it? the best epoxy in the world will not hold if that happens. how were the surfaces prepared before the glue up?

The epoxy curled? I'm new to epoxy. The handle is walnut and the blade is a 5" fillet knife I sanded the mating surfaces with 120 grit before applying the epoxy. Thanks for your reply!

 

[Cushing H.]

Overnight is too quick for wood to curl. My bet would be on the low temperatures not allowing the epoxy to harden. Think 80-100f for 24 hours

 

[Horsewright]

Glue up is done in the shop and then generally brought inside the colder months. Regardless of what it is:

 

[Natlek]

Overnight is too quick for wood to curl. My bet would be on the low temperatures not allowing the epoxy to harden. Think 80-100f for 24 hours

One hour in oven on 120F , let it cool to room temperature after that and you are ready to finish handle .

 

[Kms399]

Overnight is too quick for wood to curl. My bet would be on the low temperatures not allowing the epoxy to harden. Think 80-100f for 24 hours

Ok thank you! Hopefully I can salvage this one and I'll keep that in mind going forward

 

[velegski]

Second time in a week people(another forum)had problems with Bob Smith expoxies and handle Failures. the other was the 5 minute type.
Suggestions were
1. Better tang prep. Several guys suggested sanding tang with 120 grit. I go with 60 grit or sandblasting. 60 grit was what I was taught.
2. Over clamping. Squeezes the epoxy out of joint leaving little to nothing for it to hold with. Trying to set pins flush "could have same result.
3. Curing room temps. Most every expoxy data sheet I've read likes warm. Lower the temp longer the cure time. 70 degrees, 20 plus hours for me.
4. Scale prep. Sand back at 60 grit, then decrease with acetone followed by isopropyl alcohol cleaning. I've had some acetone leave a film that reason for following with alcohol.
5. 5 min. expoxy might be starting to set before you get scales fully attached.
As far as recommendations, I use Acraglas. Some guys like the system expixies other like West one series expoxy.
If you've got the time check out an old thread over on Knife network called glue wars. Couple guy spent month's testing out common expoxies used by knifemakers. Long but interesting read
Didn't mean to go this long but these are take aways from the other threads and my experiences.

 

[john april]

The epoxy curled? I'm new to epoxy. The handle is walnut and the blade is a 5" fillet knife I sanded the mating surfaces with 120 grit before applying the epoxy. Thanks for your reply!

i stated the handle material must have curled. the handle material must have curled if it was flat when applied and there was a space between the tang and handle material the next day?

 

[john april]

Overnight is too quick for wood to curl. My bet would be on the low temperatures not allowing the epoxy to harden. Think 80-100f for 24 hours

that is incorrect. i can curl wood on the handle by overheating it while shaping. i did it again last year with snakewood. the scales must have changed shape regardless of wether the epoxy hardened or not, if they were flat to begin with.

 

[Stacy E. Apelt - Bladesmith]

Several things are possible here:
1) improperly cured epoxy. It can be mixed wrong, too cold, too old, or not cured long enough.
2) Pins/rivets set too tight. This places pressure on the handle material making it lift at the ends.
3) Over-clamping. Clamping hard with either too tight spring clamps or mechanical clamps will both curl the wood as well as squeeze out all the resin.
4) Wood not cured enough (too green). Wood that is too moist (above 10% moisture content.
5) Wood that was cut to size and not allowed enough time for the stress of cutting to relax before sanding. Wood that was sanded flat and got hot during the sanding. Handles that were sanded to shape too soon after glue-up.

 

[Cushing H.]

that is incorrect. i can curl wood on the handle by overheating it while shaping. i did it again last year with snakewood. the scales must have changed shape regardless of wether the epoxy hardened or not, if they were flat to begin with.

Fair enough john. When i made my statement i was not thinking about the scales just sitting around - not what could happen while sanding

 

[i4Marc]

I use System Three epoxies. I used their T-88 for a long time but they have a new improved formula called Blade Pro which I am transitioning to. You can read about it here:

Blade Pro

Blade Pro epoxy adhesive is a two-component, high-performance glue designed specifically for the knife maker. This state-of-the-art adhesive forms super tough, flexible bonds to wood, Micarta, G10, and other composites.

www.systemthree.com

 

[Sando]

I use System Three epoxies. I used their T-88 for a long time but they have a new improved formula called Blade Pro which I am transitioning to. You can read about it here:

Blade Pro

Blade Pro epoxy adhesive is a two-component, high-performance glue designed specifically for the knife maker. This state-of-the-art adhesive forms super tough, flexible bonds to wood, Micarta, G10, and other composites.

www.systemthree.com

Cool. I'm going to try some.

 

[Crag the Brewer]

I use System Three epoxies. I used their T-88 for a long time but they have a new improved formula called Blade Pro which I am transitioning to. You can read about it here:

Blade Pro

Blade Pro epoxy adhesive is a two-component, high-performance glue designed specifically for the knife maker. This state-of-the-art adhesive forms super tough, flexible bonds to wood, Micarta, G10, and other composites.

www.systemthree.com

I'll admit idk much about epoxies.....
I looked up there specs on their data sheet.
It said service max temp of 160F..... is that normal temp for epoxies? (seems a hot car could be more than that in the summer, or no?)

what do the experts think?

 

[A.McPherson]

Do you leave your knives in a hot car in the summer?

They arrest people for that you know!?

Oh wait... that's children huh?

 

[john april]

west systems g flex epoxy repeatedly handles 200F according to their info. popular with knifemakers.