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For milling operations, it is very important to choose the correct milling bits size for both precision and efficiency. If the bits are the wrong size, this can cause problems like tool wear, surface imperfections, or poor machining outcomes. In this guide, we will talk about how to choose the right size for a universal milling bit. We will explain the important things to consider, how to measure them correctly, and the things that can affect your choice. So, you’ll get better quality, longer-lasting tools and a more efficient production process.
How well a milling bit works depends on its size. To choose the right milling bit size, you need to think about the following things:
Milling bits come in different diameters, which determine the size of the cuts they can make. The larger diameters mean that more material can be removed in one go, which is great for roughing or removing large amounts of material. But it can put more strain on the machine and tool, especially when it is running very quickly.
Impact on Performance:
Bigger drill bits are better for removing a lot of material and making rough holes.
Smaller diameters are better for detailed work like fine milling and finishing.
‘Cutting length’ refers to the part of the bit that actually does the cutting. For effective machining, the cutting length should be no more than a certain amount of the tool’s diameter. Otherwise, there could be vibration, which can affect how precise the machining is.
Recommended Range:
For best results, use a cutting length between 1.5D and 3D.
If the cutting length is too long, the tool might become unstable, which could affect the surface finish and the quality of the part.
So, the total length is the overall length of the milling bits, which includes the cutting length and the shank. This affects how deep the tool can go into the workpiece and how stiff the bit will be when it’s being used.
Considerations:
To give it more stability, the total length should be no more than four times the diameter. Longer tools can make it harder to be precise.
In other words, the shank diameter is important because it affects how well the bit works with the machine’s spindle and the amount of twisting force the tool can handle. The shank diameter must match the spindle size to ensure it fits well and the torque is transmitted effectively.
Typical Sizes:
Shank diameters are often available in sizes ranging from 6mm to 12mm. Larger sizes are better for heavy-duty milling tasks because they provide more rigidity.
A universal milling bit’s teeth affect how quickly it removes material and how smooth the surface is. Milling bits with more teeth usually provide a finer finish and higher cutting efficiency, while bits with fewer teeth are better suited for rough cutting and removing larger volumes of material.
Optimal Range:
2-4 teeth are perfect for rough cutting and removing material.
6 or more teeth are better for finishing and precision milling.
You must measure the milling bit correctly so that it fits the machine and works well. Here’s how you can measure the size of it:
1. Diameter Measurement
Use a digital calliper that can measure to the nearest 0.01 mm to measure the diameter of the milling bits. The most important thing is to measure the outer edge of the cutting edges. Make sure you do not include any areas that show signs of wear or damage. If it has spiral cutting edges, measure the effective cutting diameter, which may be different from the overall tool diameter.
2. Cutting Length Measurement (L1)
Then, to measure the cutting length, place the tool vertically on a flat surface and use a depth gauge to measure the distance from the tip of the tool to the point where it changes shape.
Step 1: Put the tool on a flat surface to use as a reference.
Step 2: Measure from the cutting edge to the end of the tool, making sure that the measurement is at a right angle.
3. Total Length Measurement (L)
Use a ruler or a depth gauge to measure the total length of the milling bits. The total length includes the cutting length and the shank. This measurement makes sure that the tool is not too long for the job.
4. Teeth Count
Count the number of effective cutting teeth on the milling bits. Don’t forget to leave out any teeth that won’t fit. When milling bits with different tooth arrangements (like uneven tooth spacing), only count the effective cutting teeth.
When choosing a universal milling bit, there are a few extra things to think about to make sure it’s the right fit for your milling machine and the job you need to do.
1. Material to be Cut
Material hardness is an important factor in choosing the right milling bit size. For softer materials like aluminium, smaller bits with more teeth are best, while larger bits with fewer teeth are better for harder materials like steel or titanium.
2. Cutting Speed and Power
Make sure the size of the milling bit matches the machine’s highest RPM and power levels. If you use too large a bit, the machine might struggle to handle it, which can lead to reduced performance and tool wear.
3. Type of Operation
Think about the type of milling operation being carried out:
Rough Milling: For rough cuts, use bits that are bigger and have fewer teeth. This will let you cut through the material quickly.
Finishing Milling: For finishing cuts, choose smaller bits with more teeth to achieve a smoother finish.
4. Machine Compatibility
Make sure the milling bit fits properly in your CNC machine’s spindle and tool holder. The shank (the part that the cutter fits into) needs to be the same diameter as the spindle (the part that the cutter moves along) to make sure that the cut is stable and efficient.
| Application | Recommended Diameter (D) | Recommended Cutting Length (L1) | Recommended Teeth (Z) | Shank Diameter (d) |
|---|---|---|---|---|
| General Milling | 6mm – 50mm | 1.5D – 2D | 2-4 teeth | 6mm – 12mm |
| Precision Milling | 3mm – 16mm | 1.5D – 3D | 4-6 teeth | 6mm – 10mm |
| Rough Milling | 10mm – 50mm | 1.2D – 2D | 2-3 teeth | 10mm – 12mm |
| Finishing Milling | 3mm – 16mm | 2D – 3D | 6-8 teeth | 6mm – 10mm |
| Heavy-Duty Milling | 20mm – 50mm | 2D – 3D | 2-3 teeth | 12mm – 16mm |
Choosing the right size for your universal milling bit is essential for getting the best results. To make sure your tool is right for the job, you need to know the diameter, cutting length, total length, shank diameter and the number of teeth. For an informed decision, it’s important to measure these parameters accurately and consider factors like material hardness, cutting speed, and machine compatibility.
Following these best practices will make your work better and longer-lasting, reduce times when you can’t work, and increase how much you can produce.
