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How to Drill and Tap Metal

Tapping a hole in a metal part can often remove the need for a nut. Rather than passing the bolt through the metal part and putting a nut on the back side, you can sometimes tap the threads right into the metal part and simply tighten down the fastener. Tapping metal creates threads in the metal. You can then put a threaded fastener into these threads.

To create proper threads in metal, you need to drill the correct size hole in the metal. To determine the correct size hole to drill into the metal, you will need to reference a drill and tap chart such as the one at this link:

DRILLING AND TAPPING CHART

Basic Tapping Instructions

Locate the size of the fastener you need to install in the metal. Identify the thread size and pitch on the drill and tap chart. (The fastener size is generally displayed on the left-hand side of the chart.)

Place the piece of metal on a stable work surface. Keep in mind that a properly secured work piece is a safe work piece.  When drilling and tapping, pieces can spin, move or even rise up on the tooling causing damage or worse – personal injury!

Select the “drill bit” from the set that matches the size recommended on the chart we have provided. Secure the tooling in the drill motor and put on your safety glasses and other safety equipment.

Drill the hole into or through the metal, depending on the type of metal and the application. Liberally apply cutting and tapping fluid to the “drill bit” while you drill to lubricate and cool the drill bit. Remember that slower RPM rates are better than faster ones.  Too fast and you will damage the “drill bit” or maybe even your part.

Select the tap from the tap set that matches the size of the fastener you will be installing into the metal and secure the tap in the tee-handle tap wrench.

Coat the tap with cutting and tapping fluid. Place a bit of fluid on / in the hole to be tapped. Align the tap with the drilled hole in the metal. Start threading the hole in the metal by turning the tee-handle tap wrench clockwise for a right-hand threaded hole or counter-clockwise for a left-hand threaded hole. Make sure that the tap is straight with the hole to ensure that your fastener will seat correctly.

Reverse the direction you are turning the tee-handle tap wrench if and when you feel the resistance from the tap increase. This will break the shavings and chips coming from the metal. This makes the process of threading the metal easier.

IMPORTANT: Make sure to keep any and all pressure on the tap to a minimum. you only want to press down when starting the tap.  From that point forward, you want to make sure you are only turning the tap and not leaning it from side to side or pressing down.  Some taps are hard and brittle to cut difficult metals. This means that they will snap very easily – especially smaller diameter taps.

The smaller the t-handle tap holder, the better.  Using a larger one causes broken taps often.  As long as you can comfortably turn the tap, you are good.  Look for flexing or twisting in the tap while you go.  If this happens, add more fluid, reverse the rotation for a turn or two to remove chips and continue down.

Remove the tap from the metal, wipe the cutting and tapping fluid from the surface of the metal and turn the threaded fastener into the newly threaded hole in the metal to ensure that the threads are cut correctly.

If the threaded fastener will not thread into the hole, look for debris or metal shavings in the hole and clean them out. It is almost never necessary to re-cut the threads unless your tap is the wrong size or extremely damaged.

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