How to Cut Internal Threads in 3 Steps?

The most common type of connection is still a threaded connection. To screw a screw to a workpiece, you need to have internal threads. In this article, the Internal Thread Cutting Supplier will show you how to cut internal threads on steel, cast iron, aluminum and other materials in just three steps

To cut internal threads, you will need the following tools：

Safety goggles

Twist drill bit

90° sinking hole

Internal taps (hand taps or Machine Taps)

For manual taps. Adjustable tap wrench

For machine taps: Hand drill (if box post drill is applicable)

Machine Taps

Work procedure

1. Drilling core holes (twist drill)

First, you need to drill a core hole with a twist drill.

If you wish, you can use a center punch and hit a center in the right place with a hammer. This simplifies the centering and hot tapping with a twist drill.

If you have cutting spray on hand, you should use it here. Spray the twist drill with cutting fluid. This will increase the life of the drill and improve the surface quality.

2. Sink the core hole.

Then countersink into the core hole with a 90° countersink hole and make a chamfer. The size of the countersink hole should be 10% larger than the diameter of the tap. This will give you better access to the hole when cutting the thread. It will also prevent the first and last threads from being pressed out of the hole.

3. Cutting the internal threads

As a final step, put the tap into a tap wrench (ball tap or tool holder with ratchet) and cut the threads. Carefully turn the tap into the core hole. When using a tap set, you must follow the tap sequence. You can identify the order by the ring on the shank.

In order to cut straight Internal Threads you can use a test tube and place it at right angles to the tap. Here you can use the cutting spray again. The friction between the chip and the tap cutting edge and thus also the necessary torque is reduced. This ensures better chip evacuation.

After cutting the thread, unscrew the tap in the opposite direction. Done. The thread is made.

Note: When tapping by hand, the drill should be turned back a third time after two revolutions to break the chips. This reduces the load on the drill and allows fresh lubricant to reach the cutting edge.