Epoxy issues!

K

KFU

Part Time Knifemaker, Moderator
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Sep 10, 2007
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I sent a couple of knives out to my sheathmaker the ither day. The handles were just roughed out, not finished. When I got them back I noticed both were seperating from the tang and one with ebony had cracked. It was about four days since I sent them out. I drilled the pins out and the scales literally fell off. I looked and saw no remnants of epoxy on the g10 liners, it was only in the drilled oit tang holes . So, what happened? Ive never run across thiss before. I checked and the tang was flat. Too much clamp pressure is all I can think of. I drill small holes in my liners and rough them up and the tang with 80 grit. I also wipe everything with acetone. I do clamp kind of hard with thise small bessey clamps you can hand tighten. Any thoughts? Would wet forming introduce moisture to the infinished wood?
 
You squeezed it all out brother. Then only use "Moderate" clamp pressure. All glue joints have a glue line. If there is no glue line there is not glue. Glue lines can be hard to see but they are there. The pressure from clamping is to compress both parts together and remove the air so the glue can cure. As glue dries it will contract. If you squeeze out to much glue it will contract and any bond that was there will break because there just was not enough to hold onto.
 
Same problem here, also thinking of drilling some extra holes through tang and partway through tang side of scales to give better grab...
 
The whole process has to be correct .Clean with acetone after roughing up the surfaces .Fresh epoxy ,no 5 or 10 minute stuff. Moderate pressure.
For your specifics one clue to me is the cracked ebony .That stuff likes to crack and I wouldn't doubt because of the moisture ! Finish certainly would help but I would also wrap the handle with plastic film to keep out the moisture .
 
Hollow grind a shallow area in the tang under the scales, and do a little relieving on the scales ,too. That will allow a reservoir of epoxy to stay when the clamps are on.
Drilling holes through the tang allows epoxy bridges to form from side to side, making a stronger bond.

Use the smallest power clamps you can get. All they should be doing is keeping the scales in place while the epoxy cures. They should not be squeezing anything down. Ebony will crack badly if heated even the littlest in sanding/grinding. Many people hog off the main excess with a 50 grit and lots of pressure ,then go gentle with the finer grits, thinking that will not cause any problems ..... that is a recipe for a cracked handle in a few days.

Ebony needs to be done bare handed, and touched to the forearm or cheek ever few seconds. If it feels warm, let it rest for a minute or two before going on. If you allow the core to heat up, it will start the cracks from the inside and slowly go toward the surface, showing up in days/weeks/months. Another no-no is to wipe off the handle with acetone or any liquid immediately after sanding. Let it cool off and ease out some of the sanding stress overnight, then wipe off with a tack rag. If it needs more clean-up, use an oil, like linseed or tung, and wipe some on then wipe it all off. This will remove the black "hand stain" that is the fine dust worked into the pores. It will also seal the wood a bit from swelling/shrinking.

Using Corby bolts will assure the scales won't come off, and provide their own clamping pressure. It virtually assures a perfect handle attachment every time.
 
Epoxy was squeezed out.

Drill a bunch of holes in the tang and add "divots" to the side of the scale that will be glued to the handle.
 
Also, Acetone can leave a residue. Always do the final cleaning with alcohol.
 
Thanks guys. I do drill out the tang and divot the scales. The holes were filled with epoxy. Its just never happened to me before so I thought it was odd. I did use epoxy that is usually stored inside but one of my kids pit it in the garage where it has gotten pretty cold lately. Thanks for all the replies
 
Great tips...

Get a few bags of plastic clamps from the hardware store, the yellow tipped ones are weaker than the red and they are what you want.(yes I am serious!) Use the smallest and next smallest ones, they just barely clamp down and will leave a super strong bond. I once tried to knock some drilled out scales with a 3# sledge to no avail.

I ordered some online once for a great price but they were way too strong, you should be able to clamp your finger without it hurting. It sounds funny but you need to be able to judge the strength of the clamp.
 
Here's what I'm talking about...

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