Adjustment of the bearing clearance of the lathe spindle

The adjustment of the bearing clearance of the lathe spindle is a key maintenance operation to ensure the machining accuracy and smooth operation of the machine tool. It mainly changes the preload of the bearing by ‌‌ adjusting the nut, ‌ spacer sleeve or ‌ gasket ‌, thereby controlling the clearance size. The following will explain the adjustment methods and precautions step by step. ‌ ‌

Preparatory work before adjustment

Before starting the adjustment, make sure the lathe is powered off and have the following tools and materials ready:

1.  measuring tools ‌ : ‌ dial indicator, dial indicator or ‌ feeler gauge, used for precisely measuring bearing clearance. ‌ ‌

2. Reference standard ‌ : Consult the ‌ equipment manual to obtain the standard clearance values specified by the ‌ manufacturer (typically the radial clearance is 0.006-0.01mm and the axial clearance is 0.01-0.02mm). ‌ ‌

3. Cleaning inspection ‌ : Before disassembling the ‌ main shaft end cover, clean the bearings and the surrounding area to ensure there are no worn or damaged parts. ‌ ‌

Radial clearance adjustment method

Excessive radial clearance may cause spindle runout and affect the quality of the machined surface. When making adjustments, special attention should be paid to the front bearing (taking a common lathe as an example) :

1.Loosen the locking device ‌ : Loosen the support screw or top screw of the front nut. ‌ ‌

2. Adjust the preload ‌ :

For the ‌ tapered roller bearing: Rotate the front nut to the right to move the inner ring of the bearing along the axial direction, gradually eliminating the clearance. ‌ ‌

For ‌ sliding bearings: the position of the bimetallic bearing is controlled by adjusting the front nut to keep the clearance within the range of 0.02-0.03mm. ‌ ‌

3. Verification and fixation ‌ : Manually rotate the main shaft to ensure smooth rotation without any lag. Conduct a short-term idling test and monitor the temperature rise and noise. If everything is normal, tighten the locking screw. ‌ ‌

Axial clearance adjustment method

Excessive axial clearance can cause the main shaft to run. When adjusting, the main focus should be on the rear bearing

1. Loosen the ‌ bearing lock screw ‌ : to provide space for the adjustment of the rear nut. ‌ ‌

2. Adjust the axial position ‌ : Rotate the rear nut to the right to push the inner ring of the ‌ tapered roller bearing to move axially, reducing the clearance between the main shaft shoulder and the ‌ thrust bearing. ‌ ‌

3. Control clearance range ‌ : ‌ The axial clearance should be controlled within 0.01mm to avoid overheating due to excessive tightness. ‌ ‌