Facing Lathe

How to mark a PCD on a lathe machine if it is a round flange ?

If the job is a round flange . . considering that the lead screw of cross slide has a play

First apply wet chalk powder on the face of the flange. Most of the threads will have play.To avoid the error due to thread play the reference marking also should be made in the same direction.Now draw the cross slide from inner to outer and make a marking smaller than what is required for you .Make a mark and measure the pcd. Calculate how much you have to move the slide further.You can make use of the marking on graduation handle to the distance what is to be moved carefully.If by mistake moved more than what is required you have to go back to the center and repeat the process Don't go back slightly to get your place of marking. You can mark accurately.