When should you use thread milling instead of tap machining?

With the development of cnc thread milling process, especially the advent of three-axis machining center, CNC thread milling process has gradually been widely recognized by the machining industry.

In addition, it is well known that threads can be obtained through traditional thread machining methods that we are familiar with, of which tapping is most similar to thread milling. Because they all form threads through the relative rotational motion between the tool and the workpiece. So when faced with different working conditions, how to choose the right way? This article tells you exactly what they mean.

CNC thread milling conditions:

1. Three-axis linkage (or more) machining center

2. The thread length shall not exceed 3 times the cutting edge of the tool

Advantages of CNC thread milling

1. Thread milling cutter can process threads of different diameters and the same shape.

For example, machining M15x1.0, M18x1.0, M20x1.0 threads by changing the interpolation radius with the thread milling cutter can reduce the number of tools, save tool change time, improve efficiency and simplify tool management.

2. Improved thread accuracy and finish.

Thread milling is accomplished by high-speed rotation of the tool and spindle interpolation. The cutting mode is milling, the cutting speed is fast, and the thread processed is beautiful; Tap cutting speed is low, chip is long, easy to damage the surface of the inner hole.

3. Easy discharge of internal thread.

The milling thread is chip breaking, the chip is short, and the diameter of the machining tool is less than the diameter of the machining thread hole, so the chip removal is smooth; When the tap is continuously cut, the chip is long, and the diameter of the tap is as large as the machining hole, so the chip is difficult to remove.

4. If you use a tap, of course, you can use an electric spark to break the broken part, but the process will be very complicated, and there will be losses if the parts are damaged.

If the thread milling cutter is used, first of all, it is not easy to break because of the small force; Even if broken, because the diameter of the machining hole is larger than the diameter of the tool, the broken part can be easily removed. In terms of product yield, thread milling is much higher than tapping.

5. Forming sticky chips is not easy.

For softer materials, it is easy to produce viscous chips during processing, but thread milling will rotate at high speed and break chips. Tap cutting speed is low, full thread and machining surface work, easy to cause sticky chips.

6. Require low machine power.

7. Due to thread milling chip breaking, tool part contact, cutting force is small, tap completely thread contact, force is large, the machine needs high power.

8. Tool breakage is easy to deal with.

First of all, the thread milling cutter has a small force and rarely breaks. If this happens, because the machining aperture is larger than the tool, the broken part is easy to take out; Tap force is large, chip removal is not smooth, easy to break, and large hole after breaking. It's a little easier to handle, but a lot more troublesome if it's a small hole, such as:

When machining common threads, thread milling is not cost-effective considering the cost per piece. Ordinary threads are classified as threads with a general hardness of less than 50HRC and a diameter of less than 38 mm, although this is not a clear dividing line. Ordinary taps are generally high-speed steel materials, the market price is tens of dollars, but the price of thread milling cutter is more than 10 times its price, and the life of a single piece can not exceed 10 times.

Secondly, the aspect ratio cannot be too large, usually L/D <3. Because the thread milling cutter has a unilateral force, when the thread is too long, the length-to-diameter ratio will produce a taper, and the tool can easily break.

CNC thread milling is used

1. High hardness material processing (hardness > 50HRC), suitable for thread milling, because milling chip breaking, local contact tool is small, the blade is made of cemented carbide, small wear, long service life; The general high-speed steel tap can not be processed at all, such as the use of integral carbide tap, the price is not cheap, and the price of thread milling cutter is similar. According to our existing machining experience, the efficiency and economy of thread milling is definitely higher than that of tap.

2. Compound hole (with chamfer) machining is also suitable for thread milling. Thread milling cutters have many features that can be integrated into threads and chamferes.

3. Thin wall processing, suitable for thread milling, thread milling cutter processing force is small, so small deformation. In addition, the bottom hole can be made flat, and the thread can be close to the bottom hole, so the required space is small.

4. For processing with high thread accuracy, thread milling has higher thread speed, good chip removal performance, higher thread accuracy and higher finish, which is more suitable for thread milling.

5. Soft material, titanium alloy processing, suitable for thread milling, because the thread milling cutter is not easy to produce viscous debris.

For unstable cutting, thread milling cutter can fully adapt to this situation, because its cutting principle is itself intermittent milling.



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