![]() ![]() What is a pilot hole?Ī pilot hole is drilled in the substrate timber slightly smaller than the threads of the screw itself. ![]() You would then drill a pilot hole into the wood. The piece of timber you are fixing (the first piece the screw enters) should not actually be gripped by the screws threads - the screw should pass straight through it into the substrate and the screws head serves to pull the joint up tight and with no gaps.Īlso when drilling a hole through metal to screw it to a piece of timber, it is more likely you would drill a clearance hole through the metal rather than a pilot hole. Without a clearance hole, as you wind the screw in to the two timbers a gap can develop in between them that doesn't get closed up - no matter how deeply you bury the screw head! Winding the screw head deeper wont close the gap, you will always have timber - air - timber. Having a clearance hole ensures the two materials are pulled up tight when they're screwed together. What is a clearance hole?Ī clearance hole is one drilled into the first piece of timber that is slightly larger than the screws flat shank directly under the screw head. Special countersink drill bits are available to cut the shape, although you may just be able to use a larger HSS drill bit instead if you don't have a countersink bit to hand. & don't want to countersink and fill over the screw, you can use screw cups like these instead if you want to tidy them up. If you are using dome head screws for eg. The screw head being the widest part of the screw can often be the part that causes the timber to split as you bury the screw head below the surface of the wood.īy countersinking the hole first prevents this from happening and looks neat enough to leave, or if you drill the countersink deep enough it can be filled over for painting and decorating as well. To countersink a hole is to cut a round, V shaped groove into the surface that will accommodate the tapered bottom of the screw head. But if you are doing 2nd fix carpentry that needs to be neat, drilling pilot/clearance & countersink holes is neater. If you are working with softwood like pine, you can often get away with screwing straight into the wood rather than drilling pilot holes first. You can also drill and countersink holes in wood before hammering nails in for the same reasons as above, just choose a drill bit slightly thinner than the nail itself so it will still have enough friction to hold the join together tight.
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