How to Make a Screw Thread With a Tap
Taps make internal screw threads in a pre-drilled hole. The machine screw effectively secures two pieces of material mechanically together. The tap physically removes a small amount of the hole's interior to accept the machine screw. Attention must be paid to the size of the drill bit to make the tapping hole. A drill bit that is too large will make a set of loose threads. A drill bit that is too small will cause the tap to bind and break. Does this Spark an idea?
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Instructions
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Install the correctly sized drill bit into the drill motor. See Resources for a drill bit tap chart.
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2
Drill out the tapping hole with the drill bit. Hold the drill motor as perpendicular to the surface of the material as possible. Remove the drill bit once the hole is to the correct depth.
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3
Install the square neck of the tap into the tapping wrench. Tighten the collar of the tapping wrench around the tap by turning it in a clockwise direction.
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4
Apply 4 to 5 drops of machine oil onto the tap. Squirt the same amount of oil around the interior edge of the drilled hole.
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Hold the end of the tap as perpendicular as possible to the drilled hole. Press downward with gentle pressure and turn the tap three full revolutions in a clockwise direction. Stop revolving the tap.
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Turn the tap in a counterclockwise direction until the tool is free of the hole. Clean the metal debris from the tapping tool. Squirt more machine oil on the threads of the tap.
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Insert the tap into the hole. Turn the tool six times in a clockwise direction. Reverse direction and remove from the hole. Clean the tap. Oil the tool.
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Insert the tap again. Add three more turns to the tap-turning action for every insertion until the tap reaches the correct depth. Failure to remove and clean the tap every three turns will cause the tap to break inside the hole because of accumulated metal particles from the tapping process.
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Continue to tap the hole until the end of the tap exceeds a 1/4-inch on the other side of the metal material or it has reached its full depth.
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Tips & Warnings
For a more accurately drilled hole, mount the drill bit in a drill press. The table on the drill press can be set perpendicular to the work piece.
Always wear safety glasses whenever removing material with a power tool. The action of the power tool will cause small particles to be thrown into the air.
Use the drill bit charts in the Resources section. Drilling holes of the incorrect size will either make poor threads or break the metal tap off inside the hole.
