On-Car Lathe

Use the following procedure to calibrate an On-Car brake lathe:

1. Connect the lathe to a vehicle using the appropriate adapter.

2. Attach a vise-grip dial indicator to a fixed point in the wheel well and bring the dial indicator to a flat surface on the cutting head.

3. Turn on the lathe and press the "start" button so the lathe begins to compensate.

4. Once compensation is complete, note the runout as measured by the dial indicator. Measured runout at this point is overstated given that it is outside the rotor diameter.

5. If runout is in excess of 0.1016 mm (0.004 in) (0.050 mm (0.002 in) as measured within the rotor diameter), calibration must be tightened. Follow manufacturer's instructions for tightening the calibration of the lathe. This information is found in the manual supplied with the lathe.

Important:
If the machine is taking a long time to compensate during normal use, prior to checking the lathe calibration it is recommended that the machine be disconnected from the adapter and the adapter (still connected to the vehicle) is rotated 180 degrees and the machine reattached. This will accomplish two things:

- It will re-verify the machine is properly attached to the adapter.

- It will change the location of the runout (phase) relative to the machine and thus possibly allow for quick compensation as a result of the position change.

The following information has been added as a reference to ensure your Pro-Cut PFM lathe provides a consistent smooth surface finish over long term usage.

Cutting Tips/Depth of Cut/Tip Life

The cutting tips must be right side up. Reference marks always face up. The cutting tips may not have chips or dings in the surface of the points. Cuts of 0.1016-0.381 mm (0.004-0.015 in) will provide the best surface finish and the optimal tip life.

When cleaning or rotating the cutting bits, make sure that the seat area for the tip on the tool is free and clear of debris.

Cutting Head

On each brake job, the technician must center the cutting head for that particular vehicle using one of the mounting bolt holes on the slide plate. Once the head is centered, it is vital that the technician use one hand to push the head firmly and squarely back into the dovetail on the slide plate while using the other hand to tighten the Allen-Hex bolt that secures the head. Failure to do this could result in chatter occurring during the cut.

Tool Holder Plate (Cutting Head)

The tool holder plate is the plate that the cutting arms are attached to. It can bend or break if a technician accidently runs the cuffing arms into the hub of the rotor while the rotor is turning. Cuts of more than 0.508 mm (0.020 in) can also bend this plate. Once bent, the lathe will most likely not cut properly until the tool holder plate is replaced. In order to verify the condition of the tool holder plate on a machine that will not cut right, remove the mounting bolt and remove the cutting head from the slide plate. With the cutting head titled at an angle, lay the long edge of the tool holder plate down on the flat part of the slide plate. If any gap can be seen between the edge and the slide plate, the tool holder plate is bent and the source of vibration. Also check to ensure that the cutting arms are lying flat on the upper side of the tool holder plate. If the mounting arm post is bent, it will show itself by having the back of the cutting arm lifting off the surface of the tool holder.

Gib Adjustment/Loose Gib

As wear occurs between the slide plate and the box it rides on, you must take up the slack. You do this by way of a moveable wedge, which we call the gib. Your lathe manual details the adjustment process, which you should perform when required after monthly checks or whenever surface finish is inconsistent.