I have made three drawbars for my mill . One of them is made from two long HT bolts welded together. Another is a piece of bright shaft with the threaded section of a HT bolt welded on to it. On my drawbars I have a captive thrust washer made from Phosphor bronze (about 4.0mm thick) pressed over the centering section . The centering section is slightly smaller in dia. where the thrust washer locates so that the thrust washer is free to rotate. Probably overkill.
Russell