Operating skills of manual lathes

Ⅰ. Advanced Basic Operations: Precise Control and Efficiency Enhancement

1. Precise matching of rotational speed and feed

The matching of the rotational speed and feed rate of a manual lathe directly affects the processing quality and efficiency. During rough machining, to quickly remove excess material, a low rotational speed (such as 200-300 revolutions per minute) combined with a large feed rate (0.2-0.3 millimeters per revolution) can be selected. However, attention should be paid to the tool's load-bearing capacity to avoid chipping. During finish machining, the tool should be switched to high speed (500-800 revolutions per minute) and low feed rate (0.05-0.1 millimeters per revolution) to ensure smooth cutting and achieve a smoother surface. When adjusting the rotational speed, if it is difficult to move the handle, you can gently turn the chuck to adjust the meshing position of the gears. Do not force yourself to damage the transmission.

2. Precise operation of tool setting and trial cutting

Tool setting is a crucial step to ensure dimensional accuracy. Move the tool to the end face of the workpiece, gently shake the handle to make the tool tip just touch the workpiece, and at this time, reset the scale of the middle slide plate to zero. Move the tool laterally again, turn the outer circle by 1-2 millimeters, then withdraw the tool longitudinally. Stop the machine to measure the diameter of the workpiece. Based on the difference between the measured value and the target size, precisely adjust the scale of the middle slide plate. During the trial cutting, the first cut should be "polished" cutting, that is, turning the outer circle at a small depth. The accuracy of the tool position should be confirmed through measurement to avoid workpiece scrapping due to tool setting errors.

3. The coordinated application of multiple tool rests

Ordinary lathes are usually equipped with square or hexagonal tool rests, allowing for the simultaneous installation of multiple different tools. When processing complex parts, the external cylindrical tool, internal hole tool, thread tool, etc. should be clamped and aligned in sequence in advance. During the processing, the tool rest only needs to be rotated to switch tools, reducing the tool changing time. When clamping the cutting tool, it is necessary to ensure that the height of the tool tip is consistent with the center of the spindle. This can be achieved by adjusting the tool rest gasket to avoid processing errors caused by the height of the tool tip.

Ⅱ. Special Working Conditions Response: Processing Techniques for Complex Parts

1.Anti-vibration processing of slender shafts

When processing slender shafts with a length-to-diameter ratio greater than 20, vibration is prone to occur due to insufficient rigidity, resulting in ripples on the surface. At this point, a tool rest or center rest should be used to support the workpiece. The tool rest needs to be adjusted to have a slight contact with the workpiece, providing support without hindering rotation. When cutting, reverse feed is adopted, that is, turning from the chuck towards the tailstock. The feed force is used to counteract the bending deformation of the workpiece. At the same time, sharp tools and small cutting depths are selected to reduce the influence of cutting force on the workpiece.

2. Balanced clamping of eccentric workpieces

When processing parts such as eccentric shafts and eccentric sleeves, balance irons need to be installed on the chucks to counteract the centrifugal force generated by the eccentric mass. Calculate the weight and installation position of the balance iron based on the eccentricity to ensure the stability of the workpiece during rotation. When clamping, first use a dial indicator to align the center of the eccentric circle, then slowly tighten the jaws to prevent the workpiece from shifting due to excessive clamping force. When processing, appropriately reduce the rotational speed to prevent excessive centrifugal force from causing safety accidents.

3. Efficient processing of inner holes and threads

When drilling the inner hole, due to the long overhang of the tool, vibration is prone to occur. Therefore, a thick inner hole tool holder should be selected, and the cutting depth and feed rate should be reduced. When processing blind holes, a tool withdrawal groove should be reserved at the bottom of the hole to prevent the tool from colliding with the bottom of the hole. Before turning the thread, first adjust the position of the feed box handle according to the pitch. During the trial cutting, draw a shallow thread line on the surface of the workpiece. Use a thread gauge to check if the pitch is correct. After confirming that there are no errors, proceed with the formal cutting. During the cutting process, maintain a uniform feed rate to avoid pauses in the middle that may cause the threads to become tangled.

Ⅲ. Fault Prediction and Emergency Response

1. Troubleshooting of common processing issues

If rough lines appear on the machined surface, first check whether the cutting tool is blunt and replace or resharpen it in time. If the patterns are distributed periodically, it may be that the clearance of the main shaft bearing is too large, and the preload force of the bearing needs to be adjusted. When the dimensional accuracy is unstable, first confirm whether the guide rail clearance exceeds the standard. Use a dial indicator to check the straightness of the slide movement. If necessary, adjust the gap of the insert strip. Check again if the cutting tool is loose and re-tighten the bolts of the tool rest.

2. Emergency handling of sudden malfunctions

If the spindle suddenly stops rotating during processing, the power supply should be immediately turned off. Check whether the friction clutch is slipping due to excessive cutting force. Adjusting the gap of the clutch friction plate can restore it. If the slide box cannot be moved, it may be due to the incorrect position of the feed handle or the disengagement of the hanging wheel. First, confirm the gear position of the handle, then check the meshing condition of the gears on the hanging wheel frame, readjust the hanging wheel and tighten it.

Ⅳ. Daily Maintenance and Precision Preservation

1. Pre-shift and post-shift maintenance procedures

Before starting up, check the oil levels in each lubricating oil tank, manually add grease to the lubrication points, and run the machine idle at low speed for 2 to 3 minutes to confirm that all components are operating normally. After the work is completed, clean the chips and oil stains on the bed and guide rails, wipe the tool rest, chuck and other components with a clean cloth, move the slide box to the end of the bed, turn off the power and keep a record of the equipment cleaning.

2. Regularly calibrate the accuracy

Check the levelness of the bed guide rails with a level every month. The longitudinal error should not exceed 0.02mm / 1000mm, and the transverse error should not exceed 0.04mm / 1000mm. Calibrate by adjusting the anchor bolts. Check the radial runout and end face runout of the main shaft every quarter. If they exceed the standards, adjust the bearing clearance of the main shaft to ensure stable processing accuracy.