Everyone here seems to be omitting the importance of surface prep. In addition to all that's being said, make sure you're following the instructions that come with the epoxy.
Quoted directly from BladeBond's technical data website, for example:
Surface Preparation
Probably the most misunderstood and incorrectly practiced routine in proper use of epoxy. It is VITALLY important that when gluing two things together that both mating surfaces are extremely clean and free of contaminants. and properly abraded to provide adequate "tooth" for everything to stick. However...and this is where most folks get it wrong...there is a VERY specific sequence in which this must happen, and its totally backwards from what most everyone thinks! The first step in proper surface prep is to degrease and decontaminate, which is best done with a Acetone or Denatured alcohol. Degreasing should be done in 2 stages. First thoroughly wipe the mating surfaces with a cloth dampened with the solvent, then do a second wipe down with a CLEAN DRY cloth to remove any contaminants that may have settled with the remaining solvent. Think of this as a 2 part "wash and rinse" cycle. Allow to dry thoroughly. Next we must abrade the mating surfaces to provide adequate tooth for the epoxy. Here's where I may leave most of you scratching your heads. If you can help it, do not use sandpaper to surface prep metal. Sandpaper is fine to prep wood, and even synthetics, but is not the most efficient of the abrasives to properly prep a steel surface. There are two really good methods of prepping metal; abrasive blasting using aluminum oxide and Scotchbrite abrasive surface prep pads. For knife making I prefer abrasive blasting with 80-120 grit aluminum oxide, as I feel it provides the optimum surface of totally clean fresh metal with the proper surface pattern. Scotchbrite is a close second, and I prefer the 7447 maroon pads. The key here is that your abrading CLEAN metal...not cleaning abraded metal!!! This is essential to understand, as most folks get it the other way around. The reason being is that it is much harder to remove surface contaminants that have settled into an abraded surface than it is to remove them from a smooth one.The second thing to understand is that once the metal is cleaned and abraded...DO NOT UNDER ANY CIRCUMSTANCES re-wipe with a solvent. At this point there is absolutely nothing you can do to improve the condition of the surface. Applying more solvent will only increase the chance of contamination, because most readily available solvents contain some level of impurities. If you must clean the surface of the residual sanding dust, use an air compressor to blow off the residual debris...but DO NOT apply anymore solvent! Now you may go about the business of applying the mixed epoxy and clamping the mating surfaces for the allotted cure cycle.
