Old Lathe (C6140/C620/C630) 20 Common Faults and Rapid Diagnosis & Solution Guide

Published: November 21, 2025
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This article focuses on the series of old horizontal lathes including C6140, C620, and C630, systematically sorting out 20 common faults in core systems such as spindle, feed, braking, lubrication, and electrical systems. It elaborates on the phenomenon, core causes, step-by-step diagnostic steps, and implementable solutions for each fault, and provides key accessory selection suggestions and maintenance points. Targeting engineers, combined with mechanical principles and practical experience, i

Series of old horizontal lathes such as C6140, C620, and C630 still occupy an important position in the mechanical processing field due to their stable structure and strong rigidity. However, frequent failures caused by long-term high-load operation, component aging, and improper maintenance have become a bottleneck restricting production. Targeting engineers, this article sorts out 20 typical faults from core systems such as spindle, feed, and braking, and provides accurate diagnosis methods and implementable solutions combined with mechanical principles and practical experience. It also marks key accessory selection suggestions to help quickly resume production and extend equipment service life.

I. Spindle System Faults (Core Precision Guarantee Zone)

Fault 1: Severe Heating During High-Speed Spindle Operation (Temperature Rise Exceeds 40℃)

  • Fault Phenomenon: After the spindle operates at ≥1000rpm for 30 minutes, the bearing end cover becomes hot to the touch, accompanied by slight abnormal noise, and waviness appears on the machined surface.
  • Core Causes:
    1. Excessive bearing preload (preload of double-row cylindrical roller bearing at the front end of C6140 spindle exceeds 0.03mm);
    2. Grease failure (mismatched model or deterioration);
    3. Bearing wear (rolling element spalling or cage damage).
  • Diagnostic Steps:
    1. After shutting down, touch the front and rear bearing end covers of the spindle by hand to locate the heat source;
    2. Manually rotate the spindle to feel if the resistance is uniform and if there is jamming;
    3. Disassemble the spindle box to check the bearing condition and grease properties.
  • Solutions:
    1. Adjust the preload nut. The preload of the front bearing of C6140 spindle should be controlled at the light preload level, and the idle temperature rise should be stably maintained at 15-25℃;
    2. Replace with P5-class precision bearings (C6140 recommends NN3020K double-row cylindrical roller bearing + 7210 angular contact ball bearing combination);
    3. Fill with NLGI Grade 2 lithium-based grease, with the filling amount being 1/3-1/2 of the internal bearing space.
  • Accessory Suggestion: Prioritize selecting Wuxi Sanli or Renben brand P5-class spindle bearings to ensure rotational precision and load matching.

Fault 2: Excessive Radial Runout of Spindle (Outer Circle Roundness Error > 0.02mm)

  • Fault Phenomenon: When turning a φ50mm cylindrical part, the roundness error detected by a dial indicator reaches 0.05mm, and a concave center appears on the end face.
  • Core Causes:
    1. Excessive spindle bearing clearance (radial clearance > 0.025mm);
    2. Scratched or worn spindle taper hole;
    3. Deformation of the bearing hole in the spindle box body.
  • Diagnostic Steps:
    1. Install a dial indicator on the tool rest, touch the front outer circle of the spindle with the indicator head, and record the runout value while rotating the spindle;
    2. Insert a standard test bar into the spindle taper hole and detect the radial runout of the test bar to judge the taper hole precision.
  • Solutions:
    1. Re-preload the bearing, lock the nut in sequence with a torque wrench, and perform an idle test for 10 minutes to check precision after each adjustment;
    2. For slight wear of the spindle taper hole, grinding repair can be adopted, and 2000# silicon carbide sand strip is selected as the abrasive;
    3. For deformation of the box body hole, scraping repair is required to ensure the coaxiality of the front and rear bearing holes ≤ 0.01mm.
  • Accessory Suggestion: If the spindle taper hole is severely worn, the same model spindle can be replaced, and high-quality castings with quenched and tempered treatment (HRC28-32) are preferred.

Fault 3: Spindle Braking Failure or Excessively Long Braking Time (> 3 Seconds)

  • Fault Phenomenon: After pressing the stop button, the spindle still rotates inertially for more than 5 seconds, and cannot be quickly locked during emergency braking.
  • Core Causes:
    1. Worn brake band (thickness < 3mm) or oil contamination;
    2. Deteriorated elastic force of the brake spring;
    3. Jammed or improperly adjusted brake lever.
  • Diagnostic Steps:
    1. Observe the contact area between the brake band and the brake wheel (should be ≥80%);
    2. Measure the free length of the brake spring and compare it with the standard value (standard length of C620 brake spring is 120mm).
  • Solutions:
    1. Replace with asbestos-free brake band (width matches the brake wheel, 80mm for C630), and clean the surface of the brake wheel with alcohol before installation;
    2. Replace the spring with attenuated elastic force to ensure the braking pressure reaches 0.3MPa;
    3. Adjust the brake clearance to 0.5-1mm to ensure full contact during braking.
  • Accessory Suggestion: Select oil-resistant and high-temperature-resistant asbestos-free brake bands, whose service life is 60% longer than ordinary asbestos materials.

II. Feed Transmission System Faults (Key Link for Precision Transmission)

Fault 4: Heavy Rotation of Longitudinal Feed Handle and Uneven Feed Rate

  • Fault Phenomenon: Sudden change in resistance when shaking the longitudinal feed handle, uneven rotation of the dial, and taper error when turning long shafts.
  • Core Causes:
    1. Scratched or poorly lubricated bed guideways;
    2. Excessively small meshing clearance of gears in the carriage box;
    3. Wear of lead screw and nut pair (clearance > 0.05mm).
  • Diagnostic Steps:
    1. Remove the carriage box shield and observe if there is gnawing damage on the gear meshing surface;
    2. Measure the lead screw and nut clearance (standard clearance of C6140 is 0.02-0.03mm);
    3. Check the lubricating oil film on the guideways to judge if there is dry friction.
  • Solutions:
    1. For slight scratches on the guideways, repair manually with 400# oilstone; for severe wear, milling followed by scraping is required to ensure the guideway parallelism ≤ 0.02mm/1000mm;
    2. Adjust the gear meshing clearance to 0.03-0.05mm by adding or reducing adjustment gaskets;
    3. Replace the lead screw and nut pair with precision lead screws subjected to quenching treatment (HRC58-62).
  • Accessory Suggestion: Prioritize selecting ball-structured lead screw and nut pairs, whose precision retention is 3 times higher than that of sliding type. The model suitable for C6140 is SFU3205.

Fault 5: "Crawling" Phenomenon in Transverse Feed (Tool Rest Vibration at Low Speed)

  • Fault Phenomenon: When the transverse feed speed is < 50mm/min, the tool rest jumps intermittently, and waviness appears on the machined end face.
  • Core Causes:
    1. Over-tightened gib or lubrication failure;
    2. Bent transverse lead screw (straightness error > 0.03mm/1000mm);
    3. Wear of the feed box clutch.
  • Diagnostic Steps:
    1. Loosen the gib locking screw and observe if the crawling phenomenon is alleviated;
    2. Detect the straightness of the transverse lead screw with a dial indicator;
    3. Disassemble the feed box and check the wear degree of the clutch plate.
  • Solutions:
    1. Adjust the gib clearance to ensure smooth movement of the tool rest without blockage, and control the clearance at 0.01-0.02mm;
    2. Straighten the transverse lead screw by cold straightening with a press, and correct the straightness error to ≤ 0.02mm;
    3. Replace the worn clutch plate and apply MoS₂ grease during assembly.
  • Professional Tip: Regularly fill the gib oil groove with N46 total loss system oil, at least once a week.

Fault 6: Abnormal Noise in Change Gear Box (Especially Obvious During Speed Change)

  • Fault Phenomenon: When the spindle starts or changes speed, the change gear box emits a "click" impact sound, which intensifies when the load increases.
  • Core Causes:
    1. Excessively large gear meshing clearance (> 0.1mm) or damage to the gear tooth surface;
    2. Damaged change gear shaft bearing (6205-2RS is common);
    3. Loose or missing gear positioning key.
  • Diagnostic Steps:
    1. Open the change gear box shield, manually rotate the gear, and observe the contact condition of the meshing surface;
    2. Measure the gear meshing clearance with a feeler gauge;
    3. Check the bearing operation status for jamming or looseness.
  • Solutions:
    1. Replace the damaged gear and adjust the meshing clearance to 0.05-0.08mm;
    2. Replace the 6205-2RS deep groove ball bearing, and prioritize P6-class precision;
    3. Reassemble the positioning key with transition fit (H7/js6) to ensure reliable fixation.
  • Accessory Suggestion: Select 20CrMnTi material for change gears, which are subjected to carburizing and quenching treatment, with tooth surface hardness reaching HRC58-62, significantly improving wear resistance.

Fault 7: Misthreading in Feed Box (Excessive Pitch Error When Turning Threads)

  • Fault Phenomenon: When turning M16×2 threads, pitch disorder occurs after 3-5 cutting passes, and the thread profile is discontinuous.
  • Core Causes:
    1. Inaccurate positioning of the sliding gear in the feed box;
    2. Poor meshing between the lead screw and the split nut;
    3. Incorrect change gear matching (for non-standard pitches).
  • Diagnostic Steps:
    1. Check whether the change gear ratio matches the pitch according to the lathe manual;
    2. Check if the positioning pin of the sliding gear is inserted into the positioning groove;
    3. Observe the fitting degree between the split nut and the lead screw during meshing.
  • Solutions:
    1. Readjust the change gear to ensure the transmission ratio is consistent with the pitch parameter (e.g., 1:1 for M2 threads);
    2. Replace the worn positioning pin and spring to ensure reliable gear positioning;
    3. Repair the dovetail groove of the split nut and adjust the gib to make the meshing clearance uniform.
  • Data Reference: When C6140 turns standard threads, the lead screw pitch is 12mm, and different lead conversions are realized through change gear combinations.

III. Carriage Box and Tool Rest System Faults (Core of Executive Mechanism)

Fault 8: Excessively Large Idle Stroke of Carriage Box Handwheel (> 15°)

  • Fault Phenomenon: When rotating the feed handwheel, the tool rest has no movement within the first 15°, and the subsequent movement accelerates suddenly, affecting dimensional control precision.
  • Core Causes:
    1. Excessively large clearance of the gear transmission pair;
    2. Loose connection between the handwheel shaft and the bevel gear;
    3. Wear or improper clearance of the clutch.
  • Diagnostic Steps:
    1. Mark the initial position of the handwheel, rotate it, and record the handwheel rotation angle when the tool rest starts to move;
    2. Disassemble the carriage box and check the meshing clearance of each gear.
  • Solutions:
    1. Replace severely worn gears and control the clearance of the transmission pair at 0.03-0.05mm;
    2. Re-tighten the connecting bolt between the handwheel shaft and the bevel gear, and apply thread lockant;
    3. Adjust the clutch clearance to 0.1-0.2mm to ensure stable torque transmission.
  • Accessory Suggestion: Select a scaled and non-slip handwheel with a precision grade of 1 for accurate control of feed rate.

Fault 9: Insufficient Clamping Force of Four-Jaw Tool Rest (Tool Movement During Cutting)

  • Fault Phenomenon: During heavy cutting (depth of cut > 5mm), the tool rest loosens, causing tool offset and excessive machining dimensions.
  • Core Causes:
    1. Deteriorated elastic force of the clamping spring;
    2. Wear of the clamping nut (decreased thread precision);
    3. Scratched tool rest positioning pin.
  • Diagnostic Steps:
    1. Manually toggle the tool rest to check for looseness;
    2. Measure the free length of the clamping spring and compare it with the standard value (standard length of C620 tool rest spring is 85mm);
    3. Check the fit clearance between the positioning pin and the positioning groove.
  • Solutions:
    1. Replace with a high-strength clamping spring to ensure the clamping force reaches more than 15kN;
    2. Replace the clamping nut with fine thread (M36×2) to improve locking performance;
    3. Repair or replace the positioning pin to ensure the fit clearance ≤ 0.02mm.
  • Upgrade Plan: The manual tool rest can be upgraded to a hydraulic clamping tool rest, which has stable clamping force and convenient operation. The suitable model is LD4-80.

Fault 10: Incomplete Indexing of Tool Rest (Positioning Deviation After Tool Change)

  • Fault Phenomenon: After tool rest indexing, the deviation between the tool centerline and the spindle centerline is > 0.1mm, requiring manual tapping correction.
  • Core Causes:
    1. Wear of the indexing mechanism's ratchet and pawl;
    2. Loose positioning key of the tool rest base;
    3. Abnormal speed of the indexing motor (for electric tool rests).
  • Diagnostic Steps:
    1. Observe the tool rest indexing process to judge if there is jamming;
    2. Check the meshing state of the ratchet and pawl for tooth surface wear;
    3. Measure the speed of the indexing motor (standard 1450rpm).
  • Solutions:
    1. Replace the worn ratchet and pawl made of 20Cr material subjected to quenching treatment;
    2. Re-tighten the positioning key and lock it with a set screw;
    3. Replace the indexing motor bearing (6203-2RS) to ensure stable speed.
  • Electrical Check: For electric tool rests, detect the Hall sensor signal to ensure normal output signal when indexing is in place.

IV. Braking and Lubrication System Faults (Key for Equipment Protection)

Fault 11: Poor Engagement of Electromagnetic Brake (Accompanied by "Buzzing" Sound)

  • Fault Phenomenon: When the spindle starts, the brake cannot be fully released, increasing the motor load, and the motor cannot start in severe cases.
  • Core Causes:
    1. Insufficient voltage of the brake coil (standard AC220V, measured < 190V);
    2. Excessively large gap between the armature and the iron core (> 1.5mm);
    3. Burned or short-circuited coil.
  • Diagnostic Steps:
    1. Measure the voltage and resistance of the brake coil with a multimeter (standard resistance 1.5-2kΩ);
    2. Measure the gap between the armature and the iron core;
    3. Observe if the coil has a burnt smell or external damage.
  • Solutions:
    1. Check the power supply line, replace aging wires, and ensure stable voltage;
    2. Adjust the gap to 0.5-1mm by adding or reducing adjustment gaskets;
    3. Replace the burned coil with a copper core coil of the same model (180W suitable for C6140).
  • Accessory Suggestion: Prioritize selecting full-copper coils for electromagnetic brakes, which have good heat dissipation performance and a service life more than twice that of aluminum core coils.

Fault 12: Lubricating Pump Fails to Supply Oil or Insufficient Oil Supply Pressure (Pressure < 0.1MPa)

  • Fault Phenomenon: After starting the lubricating pump, no lubricating oil flows out of the guideways, and the lubricating pressure gauge pointer shows no reading.
  • Core Causes:
    1. Low oil level in the oil tank or contaminated oil;
    2. Worn or jammed pump gear;
    3. Blocked or leaking oil supply pipeline.
  • Diagnostic Steps:
    1. Check the oil level in the oil tank and observe if the oil is turbid;
    2. Disassemble the oil pump and check the gear meshing state;
    3. Conduct segmental inspection of the pipeline and blow through the blocked part with compressed air.
  • Solutions:
    1. Supplement N46 total loss system oil to the standard oil level, and thoroughly clean the oil tank when replacing contaminated oil;
    2. Replace the worn oil pump gear to ensure the meshing clearance ≤ 0.02mm;
    3. Replace the damaged pipeline and seal the joint with sealant to prevent leakage.
  • Maintenance Points: Clean the lubricating filter weekly and replace the lubricating oil every 3 months to ensure the oil cleanliness reaches NAS8 grade.

Fault 13: Excessive Oil Temperature of Lubricating Oil in Spindle Box (> 60℃)

  • Fault Phenomenon: After the spindle operates for 1 hour, the oil temperature in the spindle box exceeds 60℃, the oil becomes thin, and the lubrication effect decreases.
  • Core Causes:
    1. Mismatched lubricating oil model (selection of N68 oil with excessively high viscosity);
    2. Blocked or poorly heat-dissipating cooler;
    3. Excessively small gear meshing clearance leading to increased friction.
  • Diagnostic Steps:
    1. Check the lubricating oil model and viscosity;
    2. Touch the surface of the cooler to judge if there is a temperature difference (should be cold under normal conditions);
    3. Detect the gear meshing clearance in the spindle box.
  • Solutions:
    1. Replace with N46 total loss system oil to ensure the viscosity is suitable for medium and low-speed working conditions;
    2. Disassemble and clean the cooler, and remove internal impurities with a descaling agent;
    3. Adjust the gear meshing clearance to 0.05-0.08mm to reduce frictional heating.
  • Upgrade Suggestion: Install an oil temperature alarm device that automatically alarms when the oil temperature exceeds 55℃ to avoid fault expansion.

V. Electrical and Auxiliary System Faults (Core of Power Guarantee)

Fault 14: Spindle Motor Fails to Start (Control Circuit Normal)

  • Fault Phenomenon: After pressing the start button, the contactor pulls in, but the motor has no movement, accompanied by a slight "buzzing" sound.
  • Core Causes:
    1. Motor phase loss (disconnection of one phase of the three-phase power supply);
    2. Jammed motor bearing;
    3. Short circuit or grounding of the rotor winding.
  • Diagnostic Steps:
    1. Measure the three-phase voltage at the motor input end with a multimeter (standard 380V±5%);
    2. Manually rotate the motor fan to judge if the bearing is jammed;
    3. Measure the motor winding insulation resistance (standard ≥ 0.5MΩ).
  • Solutions:
    1. Inspect the power supply line, replace the disconnected wire or loose joint;
    2. Replace the motor bearing (6308-2RS commonly used for C6140 motor) and fill with lithium-based grease;
    3. Replace the burned motor with a Y-series asynchronous motor (7.5kW/1450rpm suitable for C6140).
  • Electrical Tip: Detect the insulation resistance before starting the motor, and dry it in humid environments.

Fault 15: Cooling Pump Motor Burnout (Tripping or Fuse Blowing)

  • Fault Phenomenon: After starting the cooling pump, the circuit breaker trips immediately, and the motor housing becomes hot.
  • Core Causes:
    1. Jammed cooling pump impeller (blocked by cutting fluid impurities);
    2. Water ingress and short circuit of the motor winding;
    3. Excessively high power supply voltage (> 418V).
  • Diagnostic Steps:
    1. Disassemble the cooling pump and clean the chips and impurities in the impeller;
    2. Measure the winding resistance with a multimeter to judge if there is a short circuit;
    3. Detect the power supply voltage.
  • Solutions:
    1. Thoroughly clean the cooling pump impeller and pump body, and replace the contaminated cutting fluid;
    2. Replace the burned motor with a cooling pump motor with IP54 protection class;
    3. Install a voltage stabilizer to ensure the voltage is stably within the range of 380V±5%.
  • Accessory Suggestion: Select a cooling pump with a stainless steel impeller, which has strong corrosion resistance. The model suitable for C6140 is DB-12.

Fault 16: Travel Switch Failure (No Protection for Carriage Box Overtravel)

  • Fault Phenomenon: When the carriage box runs to the limit position, the travel switch does not act, causing the lead screw to jam.
  • Core Causes:
    1. Oxidation or ablation of the travel switch contact;
    2. Offset of the collision block position;
    3. Failure of the switch spring.
  • Diagnostic Steps:
    1. Manually trigger the travel switch and observe if the contactor disconnects;
    2. Check the relative position between the collision block and the switch;
    3. Disassemble the switch and check the contact state.
  • Solutions:
    1. Polish the oxidized contact with fine sandpaper, and replace the travel switch (commonly used model LX19-111) if severely ablated;
    2. Adjust the collision block position to ensure the switch is triggered 10mm before the carriage box reaches the limit;
    3. Replace the failed spring to ensure sensitive switch action.
  • Safety Tip: Inspect the travel switch monthly to ensure the protection function is effective and avoid mechanical collision accidents.

VI. Other Typical Faults (Factors Affecting Comprehensive Performance)

Fault 17: Insufficient Chuck Clamping Force (Workpiece Loosening During Rotation)

  • Fault Phenomenon: After clamping the workpiece, there is slight looseness when rotating the chuck, and workpiece displacement occurs during cutting.
  • Core Causes:
    1. Wear of chuck jaws (decreased jaw surface precision);
    2. Excessively large clearance of the chuck pull rod;
    3. Insufficient oil pressure of the hydraulic chuck (for hydraulic chucks).
  • Diagnostic Steps:
    1. Measure the roundness error of the chuck jaw clamping surface;
    2. Check the connection state between the pull rod and the chuck;
    3. Measure the hydraulic chuck system pressure (standard 0.6-0.8MPa).
  • Solutions:
    1. Repair or replace the jaws, which are subjected to quenching and grinding treatment to ensure the clamping surface roundness ≤ 0.02mm;
    2. Replace the worn pull rod bushing to reduce the clearance to 0.01-0.02mm;
    3. Adjust the hydraulic system pressure and replace the leaking seal ring.
  • Accessory Suggestion: Prioritize selecting K11 series three-jaw chucks. The model suitable for C6140 is K11-250 with a precision grade of IT6.

Fault 18: Excessive Runout of Tailstock Center (Insufficient Precision When Machining Long Shafts)

  • Fault Phenomenon: When turning a φ20×500mm long shaft supported by the tailstock center, the workpiece roundness error is > 0.03mm.
  • Core Causes:
    1. Wear or damage of the center;
    2. Excessively large clearance between the tailstock sleeve and the tailstock hole (> 0.04mm);
    3. Offset of the tailstock position (misalignment with the spindle centerline).
  • Diagnostic Steps:
    1. Detect the radial runout of the center with a dial indicator;
    2. Measure the fit clearance between the tailstock sleeve and the hole;
    3. Judge if the tailstock position is offset by the trial cutting method.
  • Solutions:
    1. Replace with a Morse No.4 high-precision center (runout ≤ 0.005mm);
    2. Repair the tailstock hole or replace the sleeve to ensure the fit clearance ≤ 0.02mm;
    3. Adjust the tailstock position to make the coaxiality between the center and the spindle centerline ≤ 0.01mm/1000mm.
  • Precision Detection: The tailstock adjustment precision can be judged by turning a test bar and measuring the roundness error at both ends of the test bar.

Fault 19: Severe Vibration of Spindle Box Body (During Heavy-Load Cutting)

  • Fault Phenomenon: During heavy cutting (cutting force > 5kN), obvious vibration occurs in the spindle box, and the machined surface roughness decreases (Ra > 1.6μm).
  • Core Causes:
    1. Loose fixing bolts of the box body;
    2. Wear of the mating surface between the box body and the bed;
    3. Unbalanced gears inside the spindle box.
  • Diagnostic Steps:
    1. Check the locking state of the box body fixing bolts;
    2. Observe if there is a gap on the mating surface (detected with a feeler gauge);
    3. Idle the spindle to judge the vibration source.
  • Solutions:
    1. Re-tighten the fixing bolts in a diagonal sequence with a torque of 200N·m;
    2. Repair the mating surface and scrape until the number of contact points is ≥ 12 points/25mm²;
    3. Perform dynamic balance treatment on the gears with an unbalance ≤ 5g·cm.
  • Structural Optimization: A shock absorption pad can be installed at the bottom of the spindle box to reduce vibration transmission. The suitable model is JB-80.

Fault 20: Lathe Bed Deformation (Precision Attenuation After Long-Term Use)

  • Fault Phenomenon: Taper error occurs when turning long shafts (> 0.05mm/1000mm), which cannot be eliminated after multiple adjustments.
  • Core Causes:
    1. Uneven bed placement (levelness error > 0.05mm/1000mm);
    2. Bed bending caused by long-term unilateral force;
    3. Insufficient aging treatment of the bed material.
  • Diagnostic Steps:
    1. Detect the bed guideway levelness with a level (evenly arrange points along the full length of the guideway);
    2. Measure the straightness and parallelism of the bed guideway;
    3. Check if the bottom support of the bed is uniform.
  • Solutions:
    1. Adjust the bed feet to ensure the levelness error ≤ 0.02mm/1000mm (longitudinal and transverse);
    2. Repair the bed bending by flame straightening and perform aging treatment after straightening;
    3. Perform grinding repair on the bed guideway to restore precision.
  • Long-Term Maintenance: When the lathe is idle, apply anti-rust oil on the guideway surface and fix the carriage box in the middle of the bed with pressure plates to avoid local force deformation.

VII. Accessory Selection and Procurement Suggestions

The effect of troubleshooting old lathes mainly depends on the quality and model matching of accessories. The following are the selection principles for key accessories:

  • Spindle bearings: Prioritize P5-class precision. C6140 uses NN3020K double-row cylindrical roller bearing at the front end and 7210 angular contact ball bearing at the rear end; C630 is suitable for NN3024K+7214 combination. Recommended brands: Renben, Wuxi Sanli.
  • Transmission gears: Select 20CrMnTi material subjected to carburizing and quenching treatment (tooth surface HRC58-62) to ensure wear resistance and impact resistance. Avoid ordinary 45 steel.
  • Braking system: Select asbestos-free brake bands with high temperature resistance (≥300℃); prioritize full-copper coils for electromagnetic brakes with insulation class F.
  • Lubrication and cooling: Select N46 total loss system oil for lubricating oil; select cooling pump with IP54 protection class to avoid motor burnout due to water ingress.

After replacing all accessories, perform an idle test (spindle idle for 1 hour, full-stroke operation of the feed system) and a load test (cutting standard test pieces) to ensure the fault is completely resolved and the precision meets the requirements.

VIII. Summary

The fault diagnosis of old lathes such as C6140, C620, and C630 should follow the logic of "first observe the phenomenon, then accurately locate, and finally solve the problem". The core is to combine mechanical structure principles with measured data to avoid blind replacement of accessories. Through the 20 typical fault solutions sorted out in this article, engineers can quickly troubleshoot problems. At the same time, by selecting high-quality and suitable accessories, not only can the fault be completely solved, but also the equipment stability and service life can be improved.

If you encounter special circumstances during fault handling or need accurate accessory matching suggestions, you can contact our technical team at any time for one-on-one professional support.