Proper Handle Prep and Epoxy Fillers

Daniel Rohde

Daniel Rohde

Knifemaker / Craftsman / Service Provider
Joined
Jul 22, 2014
Messages
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I have heard many things about proper handle prep for glue up handles(I'm principly talking about full tang knives) what I am currently doing ti roughing the tang with 80 Grit paper then simply blowing any particles off and NOT using any acetone or fluids on it, basically glueing up off the abrasive so the steel is rough and sharp to accept the epoxy..is this the best way to go about it? I'm mainly interested what condition the steel should be in for glue up.

Also I have been looking around the West Systems website and found epoxy fillers http://www.westsystem.com/ss/fillers has anyone played with these? Specifically 404 High-Density Filler

Any help would be great!
DR....
 
You do some very nice work, I have seen your knives for sale on FB. What I do is hollow grind the tang a little to lighten it and give room for epoxy to sit (I don't have to drill a bunch of holes in the tang this way, either), and if its a stainless knife I blast the tang. I don't blast carbon steel as I don't want to contaminate my blast cabinet.

Then I wipe it down with denatured alcohol. This doesn't leave a residue, and dries very quickly. Then the secret ingredient is Corby bolts. They simply aren't coming off there. Also, removing some of the wood or micarta from the tang side of the handle with a Dremel bit makes it easier to get a perfectly flat fit. Hope that helps, although from what I've seen of your work, you know what you're doing pretty well.

Sam :thumbup:
 
I drill extra holes in the tang and then grind the inside the perimeter(leaving about 1/8in around the perimeter) with a carbide Dremel cutter. Then I'll drill shallow holes in the inside of the handle scales, through the liners. When I use pins I'll use my band saw to cut multiple shallow rings around the center of them as channels for the epoxy. All these areas will allow for more surface area for the epoxy to bond to. Also, I don't feel bad clamping everything tighter as the epoxy will squish into the cavities and not out of the handle.

Oh, and I will sand then inside of the scales with 60grit and then make some scratches in the middle with the carbide cutter, like on the tang. I'm a little more conservative the the scratches though on the scales. I wipe down everything with acetone after it's done, and prior to glue up.
 
Drill holes and leave the tang at 50 grit. I also flatten the scales with a fresh 50. Windex both and use corby bolts I taper my screw holes so its easier to lineup.
 
I always drill "Epoxy Bridges" and grove the tang as well....I guess what I was wondering do you wipe down your tangs before glueing to do you just rough them up and glue right out of that?
 
Ive been doing surface prep with regular alcohol on a clean rag after light sanding of the inner part of the scales, then I use Clear JB Weld brand two part epoxy, stuff works awesome. I also add a few holes in between my pin holes to let a little glue squeeze through, also lightens up the tang.
 
you want what is referred to in the paint industry as a "break free surface". If you run water across your metal and it beads or breaks, there is oil, wax or other things in the metal that will affect the adhesion of the epoxy. For something as small as a knife handle, I used wet dry sand paper and hot water with dawn. I scrub until the metal is clean then dry it and wipe with either 90% rubbing alcohol or lacquer thinner. For the wood side, I rough sand it unless it is an oily wood then I might wipe it with lacquer thinner to remove some of the oils to aid in adhesion. Epoxy by itself or in large voids does not add to the strength of the bond.bond. In order to have more surface area you would have to make the voids in the tang have matching bumps or rises in the handle material. Kind of a lot of work for very little gain IMO. Unless someone is just beating the living tar out of thier knives, the epoxy should last for years, especially if they were pinned or bolted properly.
 
Something I tried once was drilling opposing angled holes in each scale and used a thin hidden pin (finishing nail). It's hard to explain but instead of the pin going perpendicular through the tang it went through at an angle into each scale. The regular pins went through like normal and kind of locked everything in if that makes sense.

Back on topic, I use hot water and dish soap, dry it, hit it with a heat gun and then alcohol before attaching.
 
Just seen your post. I actually just started a thread about this. I found a great video on YouTube about cleaning surfaces and testing for cleanliness. It's a but lengthy but worth it. Here's the thread with the YouTube link.http://www.bladeforums.com/forums/s...d-information-about-surface-prep-for-adhesion He explains why pure acetone, alcohol, etc will never remove all oil, and shows a simple water break test to really show if oil remains. Basically you just squirt water on it and if it beads there's oil, if it sheets there isn't. It's so sensitive that just leaving the cleaned part in open air for a day will cause it to fail the test because of oil in the air. Good stuff. He explains it better than I can on here.
 
Ryan, thanks for that post as well. Regarding Acetone.....the acetone I have leaves a film behind. I've scrubbed blades clean and then put acetone on it just to verify....yep....film present. I still use acetone, but always finish off with Windex. I may just start using the comet!
 
I remember reading in the paperwork that came with Gflex that sanding the steel after applying the epoxy would greatly increase adhesion.
 
I usually sand the tang, pins, and back side of scales or spacers to get them all scratched up. I always drill extra holes in my tangs and then drill holes into the spacer material going into the scale material just a bit. I like to make sure the holes in the scales and tang match up so I get bridges of epoxy that can go from one scale in one side into the other scale. I then wash the tang with dawn in super hot water then wipe everything down with acetone before assembling.

Jay
 
I read a NASA post on surface prep and they said that simple exposure to air allows corrosion to start. So they said after sanding for surface prep, leave the sanding dust, apply epoxy, lightly sand again as no air will come in contact with it. Squeeze out excess. The metal sanding metal dust mixes with the epoxy and improves its adhesion.
 
I make mostly Stainless full tang knives.

I have my blade finished and taped up. I taper the drilled tang on the platen down to 120 grit and then on to the bench where I have Loveless style bolts read.

I have finished the scales to 120 g as well. I use G-Flex only. The mechanical Loveless are really what holds the scales. The G-Flex does give a strong bond, but its really to seal the scales, tang & liners all together so moisture doesn't get under the scales.'

I also butter up the bolts and put a few drops into the counter sunk holes for the Loveless screws & Nuts of the G-flex. I only had one handle seperate since I started almost 20 years and its was Devcon epoxy.

The man I made it for would let the knife sit next to the open flame burner on his stove. There were burns marks on the scales.:rolleyes:

I don't really blame the Devcon. I just know its not as long lasting as G-flex which is used to put boats & planes together.
 
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