I found an old clock motor years ago, with a 1/8 inch output shaft. I built that up to about 1/4 inch with a section of vinyl tubing . I either slide the vinyl shaft into the female ferrule and wrap a bit of masking tape over the joint or just butt the rod up against the output shaft and wrap the joint with masking tape. So far after a handfull of graphite rods and more than a dozen cane rebuilds I have never had a failure or felt a need to do any different. I have considered building something a bit fancier but the problem is whatever I come up with would have to fit a wide variety of sizes. This is easier.
AgMD