How to calibrate the center rest of a lathe

The core of the calibration of the ‌ lathe center rest is to measure the runout of the workpiece with a dial indicator and eliminate the deviation by adjusting the center rest outriggers. Here are the detailed steps and key points ‌ :

Preparations before calibration

1. Workpiece clamping ‌ : Use a three-jaw chuck to clamp one end of the workpiece, and support the other end with a center rest. Ensure that the machined surfaces (outer circle and end face) at both ends of the workpiece have been precisely machined, and the coaxiality error is less than 0.02mm. ‌ ‌

2. Tool check ‌ :

Adjust the preload of the dial indicator to 1-2mm, gently push the measuring rod three times, and confirm that the pointer can return to zero (otherwise, replace it). ‌ ‌

The watch stand is fixed on the lathe guide rail to prevent shaking. ‌ ‌

Step-by-step meter calibration process

1. Install the dial indicator ‌ :

Radial measurement: The gauge head is vertically pressed against the outer circle of the workpiece, and four points of 0°, 90°, 180°, and 270° are marked on the surface. ‌ ‌

Axial measurement: The gauge head is vertically attached to the end face of the workpiece, and marked at the same position. ‌ ‌

2. Preliminary measurement ‌ :

Rotate the workpiece manually once and record the readings at each point. For example:

Radial runout: 0°=0.01mm, 90°=0.03mm, 180°=0.02mm, 270°=0.04mm.

(2) Axial runout: 0°=0.01mm, 180°=0.02mm. ‌ ‌

3. Adjust the center rest ‌ :

If the reading at a certain point is too high (for example, 0.03mm in the 90° radial direction), gently tap the side leg with a copper hammer to reduce the height of the workpiece (the tapping force should be small to avoid overadjustment). ‌ ‌ ‌

Repeat the measurement until the runout of all points is ≤0.02mm (for precision machining, it should be ≤0.01mm). ‌ ‌

4. Preload verification ‌ :

Remove the tailstock center and check with a dial indicator whether the workpiece has been lifted by 0.05-0.08mm (indicating that the preload is appropriate). ‌ ‌

Press the center frame cover tightly and lock the bolts. ‌ ‌

Key points to note

1. Key points of ‌ measurement ‌ :

The meter head must be perpendicular to the surface of the workpiece. Tilting will cause reading errors. ‌ ‌

Record the data once for each 90° rotation. Rotate at a constant speed to avoid vibration. ‌ ‌

2. Frequently Asked Questions ‌ :

Repeated excessive jumping: Check whether the workpiece is bent or the chuck clamping is too short (> 10mm). ‌ ‌

The dial indicator does not return to zero: Clean the probe or replace the battery (for electronic watches). ‌ ‌