I dont have a lathe and needed to turn down an M6 bolt to replace a broken seat stud.
It is not visible once cover fitted, but I like to play
I am sure many of you will have used a drill mounted in vice with a file to shape, but it works even better if you have a grinding wheel.
Mount the bolt in drill and whilst operating drill and grinding wheel, shape the bolt against the wheel.
This gives a much more even finish.
Drilled out the stud and counter sunk.
2014_1122kparts0052 by
nitram2010, on Flickr
2014_1122kparts0054 by
nitram2010, on Flickr
I later added a bevel to allow bolt to fit counter sunk.
Will need welding to finish