Broaching Keyway

I agree with you, Alan. Methods explained are very interesting....

Alan I can see your point,if you do not try yourself one does not learn ,so have a go, I make my boring tools from silver steel just as I did 55years ago during apprenticeship,in those days the holes in the bar were square,no doubt laboriously filed from drilled holes,since those days I cheated a bit ,Just drilled a hole int the bar and used a round HSS toolkit..now should the tool bit be the same diameter as the required keyway just grind a short length of the tool bit,down to the radius so you produce a flat of the diameter in width, for small keys side clearance is not required,just some clearance ground on the end, this make a nice broaching tool. One snag is the size of your lathe,and the size of the saddle hand wheel,as it takes some effort to plane out a long keyway. also be aware that the side load on the boring bar tool holder will have a tendency to rotate the tool post so you may be merrily adding small cuts and not get very far as the tool post slips.This method of using round toolbits is ok up to about three eighths of an inch,above this they are too weak and break,Care must be taken with set up to ensure the keyway is central in the hub,a wonky keyway which is off to one side and nor truly radial looks awful.One thing myself and fellow apprentices found was that the lathe spindle did not tend to rotate when cutting ,just put the lathe in low speed and back gear ,the lathes used were a large Willson and a Boxford neither had a spindle lock.