Epoxy for scales

D

DougB2

Joined
Jun 6, 2009
Messages
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My question is about the best way to use epoxy with my handle scales. I use two-part epoxy, I get it as close to a 1:1 mixture as possible, and I mix it thoroughly. I coat the scales completely with the epoxy and clamp the scales to the tang. I always have epoxy oozing out the sides, expecting that I've fully secured the scales. (And I always have another mechanical means of holding the scales, like corby bolts, not just epoxy.) Several of my knives have gaps between the scales and tang, even though there was a lot of epoxy in there. When I clamp the scales, I make them as tight as possible.

Should I clamp the scales on really tight? Or is that forcing too much epoxy out, leaving the gaps when the epoxy finally cures? I'd appreciate any thoughts on this!
 
Some epoxies have a slower cure time. Those are the ones that lend themselves better to handle manufacture.
 
DougB2 said:
Thanks for the info! Does it matter how tightly they're clamped?
Click to expand...

Yes, don't clamp too tightly. Not sure why you have gaps between scales and tang? If both are flat you won't have gaps.
I like the Irwin Quick Grip clamps because you can squeeze those and not worry about over tightening; they don't get super tight.
 
If you use mechanical fasteners, I would suggest you don't use clamps at all. If your handle scales are not perfectly flat against the tang and you clamp them tightly against the tang, as soon as you take the clamps off, the scales will start to pull off the tang and there is a chance, the epoxy won't be strong enough to hold them together. If you don't clamp, any voids will be filled out with epoxy and you won't have any gaps.
 
You must start with a flat tang and a flat scale. Get something you know to be flat. I use a granite slab that is the cutout from a sink in a countertop. A piece of glass or even a piece of MDF particle board will work. Use that as a surfacing plate. I make sure my scales are dead flat. To do this I flatten them with 120, then 220 grit sandpaper on the granite, then hold them up back to back with a bright shop light backlighting them. You should not see any light a the faces, all around the edges. The tang needs to be equally flat. Like, really flat. Don't compromise here. You will get a feel for it in the way you hold the scale on the surface plate - concentrate on holding it uniformly with light pressure and not scrubbing off the edges (making them canoe shaped). FLAT!!!

I drill the back sides with 30 or 40 dimples, just about 1/16" to 1/8" deep, 1/8" diameter holes. This gives the epoxy lots more surface area and some place to go instead of squeezing all out. Make sure the edges of the holes are within about 1/8" of the edge of the scale, but don't blow through the front surface.

And DON'T clamp them too hard. Just the "clothesline" style spring clamps is fine. No need for a hard squeeze with C-clamps! Also, do not take the clamps off part way through to check on them. Leave them on for the full curing time, at least 12 hours (assuming you are using a quality epoxy like G Flex, not the 5-minute rapid cure).

If you have to rely on the clamps to take out a bow or something not flat you are not getting them flat enough. Finger pressure will show you if you are going to be successful.

Use enough epoxy to coat the surfaces. I use a popsicle stick to make sure the drilled dimples and any holes in the tang are full. You will see air bubbles in the holes so keep working epoxy down there until the air bubbles pop out.
 
Thanks for all of the guidance! I do have some Irwin Quick Grips, and I'll use them instead of the stronger metal clamps. I've never drilled dimples in the tang side of the scales, although I always take the corner of a file and gouge some grooves into the material. I clean out any dust and debris before attaching them. I'll try the dimples on the next one. Some have turned out very nicely but I'll take your suggestions and be more careful from now on. Thanks again!
 
I hollow out scales up to 1/8~1/16" from the edge. That way only the outer part needs to be flat. In the middle there is a cavaty to fill with epoxy.
Maybe you make thin knives. If so it may be the flex of the blade
 
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