Metal-to-Metal
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Drill a hole through the materials you want to join. Drill the appropriate size hole for the screw.
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Apply an anaerobic screw thread locking sealant evenly onto the threads of the screw if screwing metal or metal alloys together. There are a variety of thread locking sealants on the market at most hardware stores. Read the description on each label to see which best fits your needs. Use a small brush if necessary to evenly coat the threads.
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Give the thread locking sealant at least 8 hours to partially cure and 24 hours to fully cure. This will both lock the screw in place when fully cured and protect against vibration since the sealant will not only glue the screw in place but act as a shock absorber between the metal screw and the metal to which it is attached. The better locking sealants will require at least 30 foot-pounds of torque to break the seal, often more when fully set.
Wood-to-Wood
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Drill a hole through the materials you want to join, making certain to use the correct size drill bit for the size screw you will be using.
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Mix the epoxy resin with the hardener on a piece of cardboard or small disposable plastic container using a scrap piece of wood.
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Fill the holes in both pieces of wood with flexible epoxy sealant. There are many brands available at hardware stores so read the labels to make certain you get the best type for your application.
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Apply the epoxy sealant to the threads of the screw and screw it into place, securely seating the screw. There will likely be seepage of the epoxy sealant from the drilled holes. Use a putty knife to scrape away any excess and a dry clean cloth for whatever epoxy remains on the surface.
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Apply a bead of epoxy sealant around the edges of the screw head if it is a round screw head. Apply the sealant over the top and around the edges of flat head screws. If the wood is sufficiently heavy, turn the screw into the wood an extra 1/32 of an inch and then cover with epoxy and smooth even with the wood surface using the putty knife.