How to operate a lathe？In this blog, I will introduce you to a few common points of lathe machining.
How to process the shape of the ball
1. Machining method
Spherical machining can be achieved by installing a special spherical tool holder, or by manually rotating the tool holder to achieve the circular motion of the tool to cut the sphere. In general, the smooth spherical effect is achieved by gradually turning polygons close to the spherical contour, and finally fine trimming.
2. Required tool
Usually, a round-nose cutter or a special spherical cutter is used for machining to adapt to circular cutting. In addition, the spherical tool holder is a special accessory for spherical turning and can be mounted on the bed to manually adjust the feed path of the tool.
Machining a crankshaft
1. Steps
Find the center: mark the center of the main shaft and eccentric shaft on the workpiece.
Clamping workpiece:the workpiece is clamped on the fixture, and the center of the eccentric shaft of the workpiece is aligned with the spindle center of the lathe.
Processing of the main shaft: The outer circle of the main shaft is turned first.
Processing eccentric shaft part:Adjust the fixture, so that the center of the eccentric shaft and the lathe spindle coaxial, eccentric shaft processing.
Finishing: The use of finishing tools to meet the size and surface finish requirements.
2. Key point
Fixture selection:Eccentric fixture is crucial to ensure that the different coaxial segments of the crankshaft are aligned.
Repeated Clamping Accuracy:Any eccentric machining must accurately adjust the workpiece to prevent eccentric accuracy errors.
Avoid vibration:eccentric rotation will produce unbalanced force, pay attention to adjust the cutting speed to avoid tool vibration affecting the surface quality.
Taper machining method
Center angle adjustment method:By adjusting the position of the tailstock, the lathe spindle and the tailstock form a small angle, so that the tool is fed along the taper angle to machine the taper. Suitable for machining short tapers with high precision.
Center angle fixing method: The centre angle turning device is fixed tothe lathe, and the required taper angle is set directly, so that the turning tool can machine the taper along a fixed path.
Tool holder angle adjustment method:the tool holder is rotated to the required taper angle, so that the tool is fed along the inclined angle and small taper parts can be machined.
Tailstock offset method:the tailstock is offset to one side, suitable for machining long tapered parts, but the angle adjustment must be carefully controlled, suitable for machining longer and less precise workpiece requirements.
Machining parts of specified radius
1. Steps
Determine the radius size:Determine the required radius by the measuring tool, and adjust the tool position according to the radius size.
Use arc templates or gauges:In the process of processing, prefabricated radius gauges can be used to check the processing size to ensure that the processing radius meets the requirements.
Feed Control: Manually adjust the tool holder and gradually cut out the specified radius area.
Finishing and finishing:After rough machining is completed, fine finishing is carried out to achieve the required radius and finish.
2. Tools
Round nose knife, gauge or radius template to help achieve radius accuracy.
Thread Machining
1. Steps
Spindle Speed adjustment:Select a lower spindle speed according to the type of thread to facilitate accurate feed control.
Tool selection and installation:Select the threading tool, install and align the centre of the workpiece.
Feed Adjustment:Adjust the lathe feed mechanism according to the thread specification (e.g. pitch), usually controlled by the gearbox.
Preliminary Cutting:Shallow feed, first cut out the thread contour, then gradually deepen.
Multiple turning:After each cut, the feed is increased slightly until the target depth is reached to complete the thread forming.
Finishing:Use special tools to finish the surface of the thread to achieve a higher finish.
2. Key point
Stable Cutting speed:Maintain a constant spindle speed to avoid uneven threading.
Precise Feed control:Select an appropriate cutting depth according to the workpiece material to reduce tool wear.
Use Lubricants: Reduce cutting heat and tool wear, improve surface finish.
Lathe machining of different materials
1. Hard steel
When machining hardened steel, it is necessary to select high-hardness tool materials, and strictly control the amount of feed and cutting depth to avoid excessive heat and affect the machining quality.
Cutting tools:Carbide cutting tools or ceramic cutting tools are usually used, because of their high hardness and wear resistance, suitable for cutting hardened steel.
Cutting speed:It is recommended to choose low cutting speed to reduce tool wear and control the processing temperature, and the general cutting speed is controlled at 10-20 m/min.
Lubrication and cooling:Use sufficient coolant to reduce heat and avoid heat accumulation causing tool wear or deterioration of workpiece surface quality.
2. Stainless steel
Stainless steel has high strength and toughness, it is easy to produce hardening phenomenon during machining, and the tool surface is easy to adhere, resulting in a decrease in surface quality.
Tool selection:Use tungsten carbide tools with good heat resistance or high-speed steel tools, and the cutting angle should be slightly larger to reduce machining resistance.
Cutting speed:Controlled at 60-90 m/min to avoid hardening due to excessive speed.
Feed amount:Use smaller cutting depth and feed amount, cutting step by step to prevent hardening of materials.
Coolant:Sufficient coolant can effectively reduce the temperature, reduce the sticking phenomenon, to ensure the surface quality.
3. Titanium
Titanium has low thermal conductivity, and the cutting heat is concentrated in the cutting edge of the tool, which is easy to cause tool wear during machining. The Young’s modulus of titanium is low, resulting in large vibration during machining, and the surface quality is not easy to control.
Tool selection:Preferably coated carbide tools, such as TiAlN coated tools, increase heat resistance and wear resistance.
Feed mode: Select smaller feed rate and depth of cut, use slow feed mode to reduce cutting force.
Cooling and lubrication:High pressure coolant is injected directly into the cutting area to help dissipate heat and reduce tool wear.
4. Rubber
Rubber is a flexible material, elastic, easy to stretch and deformation in cutting, and not easy to produce continuous chips, surface processing is difficult.
Tool selection: Use a sharp small front angle tool, the cutting edge should be sharp, and the cutting force should be minimised when cutting.
Cutting speed:The cutting speed of rubber can be appropriately increased to 100-300 m/min to avoid low speed cutting resulting in material stretching.
Cooling and lubrication:Usually do not use coolant when processing rubber, to prevent the coolant from affecting the quality of the rubber surface, may be appropriate to add soapy water as lubrication.
Clamping and feed:Usually do not use coolant when processing rubber, to prevent the coolant from affecting the quality of the rubber surface, may be appropriate to add soapy water as lubrication.
