Vickers hardness HV (mainly for surface hardness measurement)
Use a diamond square cone indenter with a maximum load of 120 kg and a top angle of 136° to press into the material’s surface and measure the diagonal length of the indentation. This method is suitable for assessing the hardness of larger workpieces and deeper surface layers.
Leeb hardness HL (portable hardness tester)
The Leeb hardness method is used to test the hardness of materials. The Leeb hardness value is determined by measuring the rebound velocity of the impact body of the hardness sensor in relation to the impact velocity at a distance of 1mm from the surface of the workpiece during the impact process, and then multiplying this ratio by 1000.
Advantages: The Leeb hardness tester, based on the Leeb hardness theory, has revolutionized traditional hardness testing methods. The small size of the hardness sensor, similar to that of a pen, allows for handheld hardness testing on workpieces in various directions at the production site. This capability is difficult for other desktop hardness testers to match.
There are various tools for machining, depending on the type of material being worked with. The most commonly used tools are left-leaning, right-leaning, and middle-leaning, as illustrated in the figure below, based on the type of boss being machined. Additionally, tungsten carbide tools with high-temperature coatings can be used to cut iron or wear-resistant materials.
2. Tool inspection
Carefully inspect the cutoff knife before use. If using high-speed steel (HSS) cutting blades, sharpen the knife to ensure it is sharp. If using a carbide parting knife, check that the blade is in good condition.
3. Maximize the installation rigidity of the cutting knife
Tool stiffness is maximized by minimizing the length of the tool protruding outside the turret. Larger diameters or stronger workpieces need to be adjusted several times when the tool cuts into the material during parting off.
For the same reason, the parting is always done as close to the chuck as possible (usually around 3mm) in order to maximize the stiffness of the part during the separation, as shown in the figure.
4. Align the tool
The tool must be aligned perfectly with the x-axis on the lathe. Two common methods for achieving this are using a tool setting block or a dial gauge, as shown in the image.
To ensure that the cutting knife is perpendicular to the front of the chuck, you can use a gauge block with a parallel surface. First, loosen the turret, then align the edge of the turret with the gauge block, and finally, retighten the screws. Take care not to let the gauge fall off.
To ensure that the tool is perpendicular to the chuck, you can also use a dial gauge. Attach the dial gauge to the connecting rod and place it on the rail (do not slide along the rail; fix it in place). Point the contact at the tool and move it along the x-axis while checking for changes on the dial gauge. An error of +/-0.02mm is acceptable.
5. Check the height of the tool
When using tools on lathes, it’s important to check and adjust the height of the parting knife so that it is as close to the centerline of the spindle as possible. If the parting tool is not on the vertical centerline, it will not cut properly and may be damaged during machining.
Just like other knives, parting knives must use a lathe level or ruler so that the tip is on the vertical centerline.
6. Add cutting oil
When using a regular car, do not use automatic feeding, and be sure to use a lot of cutting oil, because the cutting process generates a lot of heat. So, it gets very hot after cutting. Apply more cutting oil to the tip of the cutting knife.
7. Surface velocity
When cutting off on a general car, the cutter should usually be cut at 60% of the speed found in the manual.
Example: Custom precision machining with a carbide cutter calculates the speed of a 25.4mm diameter aluminum and 25.4mm diameter mild steel workpiece.
First, look for the recommended speed, High Speed Steel (HSS) Parting Cutter (V-Aluminum ≈ 250 ft/min, V-Steel ≈ 100 ft/min).
Next, calculate:
N Aluminum [rpm] = 12 × V / (π × D)
=12 in/ft × 250 ft/min / ( π × 1 in/rpm )
≈ 950 revolutions per minute
N steel [rpm] = 12 × V / (π × D)
=12 in/ft × 100 ft/min / ( π × 1 in/rpm )
≈ 380 revolutions per minute
Note: N aluminum ≈ 570 rpm and N steel ≈ 230 rpm due to the manual addition of cutting oil, which reduces the speed to 60%. Please note that these are maximums and security must be considered; So smaller workpieces, regardless of the calculation results, cannot exceed 600RPM.
If you wanna know more, please feel free to contact info@anebon.com.
At Anebon, we firmly believe in “Customer First, High-Quality Always”. With over 12 years of experience in the industry, we have been working closely with our clients to provide them with efficient and specialized services for cnc turning components, CNC machined aluminum parts, and die-casting parts. We take pride in our effective supplier support system that ensures excellent quality and cost-effectiveness. We have also eliminated suppliers with poor quality, and now several OEM factories have cooperated with us as well.
Post time: Jul-29-2024