- Use a respirator and eye protection. These two protects the most vulnerable parts of your body when handling tungsten carbide. Using a respirator is important especially in situations where there is poor or no ventilation available. Even when a place is well-ventilated, using a respirator is still recommended.
- Full body protection. Wearing protective clothing for the entire body is also important. It helps prevent allergic reactions on the skin when it comes to contacts with tungsten carbide.
- Skin protection. Gloves are a must-wear when handling tungsten carbide. Its also important to apply barrier cream on the skin to add another layer protection against tungsten carbide dust or mist when working.
- Stay away from tungsten carbide work areas. if you have no business being in an area where there's work on tungsten carbide going on, stay out of it.
Sunday, November 14, 2010
How to Safety Handling Tungsten Carbides
Carbide Cutting tools benefits
Toughness - Carbide cutting tools on their own are tough, but with the added coatings available, they become almost indestructible tools for the machine industry to use in their cutting machines. Resistant to abrasions, thermal deformation and other material wear, carbide produces a quality cut and rarely needs repair or replacement.
Value - Because Carbide cutting tools work at high speeds without warping, and cut through even the toughest of materials, it keeps the assembly line working fast and productively. Its value is immense in that productions loads can be increased without extra wear and tear on parts, as well without any damage to the product being produced. Overall, this make carbide cutting tools a preference over high speed steel for machinists and other industry professionals.
Thursday, April 29, 2010
Cutting Speeds & RPM Calculations
Cutting Speed for Milling- Cutting speed is the speed at the outside edge of the milling cutter as it is rotating. This is also known as surface speed. Surface speed, surface footage, and surface area are all directly related. Two wheels can illustrate a nice example of this. Take two wheels, one wheel which is three feet in diameter and the other wheel which is one foot in diameter, roll each wheel one complete turn (Figure 1).
Figure 1
Which wheel traveled farther? The larger wheel traveled farther because it has a larger circumference and has more surface area. Cutting speeds work on the same principle. If two cutters of different sizes are turning at the same revolutions per minute (RPM), the larger cutter has a greater surface speed. Surface speed is measured in surface feet per minute (SFPM). All cutting tools work on the surface footage principal. Cutting speeds depend primarily on the kind of material you are cutting and the kind of cutting tool you are using. The hardness of the work material has a great deal to do with the recommended cutting speed. The harder the work material, the slower the cutting speed. The softer the work material the faster the recommended cutting speed (Figure 2).
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Increasing Cutting Speed |
The hardness of the cutting tool material has a great deal to with the recommended cutting speed. The harder the cutting tool material, the faster the cutting speed (figure 3). The softer the cutting tool material the slower the recommended cutting speed.
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Increasing Cutting Speed |
Figure 3 |
The depth of cut and the feed rate will also affect the cutting speed, but not to as great as an extent as the work hardness. These three factors; cutting speed, feedrate and depth of cut are known as cutting conditions. Cutting conditions are determined by the machinability rating. Machinability is the comparing of materials on their ability to be machined. From machinability ratings we can derive recommended cutting speeds. Recommended cutting speeds are given in charts. These charts can be found in your Machinery’s Handbook, textbook or a chart given to you by your tool salesperson. In Table 4 you will find a typical recommended cutting speed chart.
Milling-Machine Operations
Table 4. Recommended Cutting Speed for Milling in Feet per Minute (fpm)
| Hardness, | Cutting Speed, fpm | |
High-Speed Steel | Carbide | ||
Plain Carbon Steel, AISI | to 150 | 110 | 600 |
The milling machine speed must be set so that the milling cutter will be operating at the correct cutting speed. To set the proper speed we need to calculate the proper revolution per minute or RPM setting. We stated earlier that cutting speed or surface speed would change with the size of the cutter. So to keep the surface speed the same for each size cutter we must use a formula that includes the size of the cutter to calculate the proper RPM to maintain the proper surface footage.
Calculating RPM- The RPM setting depends on the cutting speed and the size of the cutter. The RPM setting will change with the size of the cutter. As the milling cutter gets smaller the RPM must increase to maintain the recommended surface footage. Again, take the case of the wheel. Think of the cutter as a wheel and the cutting speed as a distance. A larger wheel (cutter) will need to turn fewer revolutions per minute to cover the same distance in the same amount of time than a smaller wheel (cutter). Therefore, to maintain the recommended cutting speed, larger cutters must be run at slower speeds than smaller cutters.
The milling machine must be set so that the milling cutter will be operating at the proper surface speed. Spindle speed settings on the milling machine are done in RPMs. To calculate the proper RPM for the tool we must use the following formula:
Cutting speed (CS) X 4
Diameter of cutter (D)
This simplified version of the RPM formula is the most common formula used in machine shops. This RPM formula can be used for other machining operation as well.
Lets put this formula to work in calculating the RPM for the machining example below. Use the recommended cutting speed charts in Table 5.
Milling-Machine Operations
Table 5. Recommended Cutting Speed for Milling in Feet per Minute (fpm)
| Hardness, | Cutting Speed, fpm | |
High-Speed Steel | Carbide | ||
Plain Carbon Steel, AISI | to 150 | 110 | 600 |
AISI B1111, AISI B1112, AISI B1113, Steel | 140 to 180 | 140 110 to 200 | 650 400 to 1200 |
Plain Carbon Steel, AISI 1040 to 1095 | 120 to 180 180 to 220 220 to 300 | 195 | 600 |
All Alloy Steels Having .3% or Less Carbon Content: | 180 to 220 220 to 300 300 to 400 | 80 | 350 |
All Alloy Steels Having More Than .3% Carbon Content: | 180 to 220 220 to 300 300 to 400 | 80 | 325 |
A milling cut is to be taken with a 0.500 inch high speed steel (HSS) endmill on a piece of 1018 steel with a brinnel hardness of 200. Calculate the RPM setting to perform this cut.
Cutting Speed = 90 (fpm)
Diameter of Cutter = 0.500
Since the available spindle speed settings are generally not infinitely variable, the machine cannot be set precisely to the calculated RPM setting. Some judgment must be made in selecting the speed to use. Try to get to the speed which is nearest to the calculated RPM, but if you can’t consider these conditions. Are you roughing or finishing? If you are roughing, go slower. If you are finishing go faster. What is your depth of cut? If it is a deep cut, go to the slower RPM setting. Is the setup very rigid? Go slower for setups that lack a great deal of rigidity. Are you using coolant? You may be able to go to the faster of the two settings if you are using coolant. The greatest indicator of cutting speed is the color of the chip. When using a high-speed steel cutter the chips should never be turning brown or blue. Straw colored chips indicate that you are on the maximum edge of the cutting speed for your cutting conditions. When using Carbide, chip colors can range from amber to blue, but never black. A dark purple color will indicate that you are on the maximum edge of your cutting conditions. Carbide cutting tools are covered in much greater detail in other section of your learning materials.
Let’s try some more examples.
A milling cut is to be taken with a 6.00 inch (HSS) side milling cutter on a piece of 1045 steel with a brinnel hardness of 300. Calculate the RPM setting to perform this cut.
Cutting Speed = 55 (fpm)
Diameter of Cutter = 6.00
A 1-inch (HSS) drill is used on a piece of 1010 steel with a brinnel hardness of 100. Calculate the RPM setting to perform this drilling operation.
Cutting Speed = 140 (fpm)
Diameter of Cutter = 1.00
A milling cut is to be taken with a 3.00 inch carbide face milling cutter using coated inserts on a piece of 4140 alloy steel with a brinnel hardness of 200. Calculate the RPM setting to perform this cut.
Cutting Speed = 400 (avg. fpm)
Diameter of Cutter = 3.00