04-09-2015, 06:58 PM
(04-07-2015, 10:00 PM)Mayhem Wrote: <snip>
I'm thinking of using 1/2" ground for all 3 drawbars and then turning down the diameter for a M12 thread. The tolerance on the ground bar should be good for the 1/2-12 and 1/2-13 drawbars. I would then use the hex bar for the wrench end.
They have a minimum $50.00 order, so I may pick up some 25mm round stock as well. Given that I am going to probably have more use for round stock than hex, having some 25mm stock might be a better choice. The also have off cuts...
That's a good plan. You would only have to turn the last 25-30mm of it for the M12 thread.
Getting the 25mm stock would allow you to mill nice hex heads for the bars, and you could choose to pin the heads on or weld. Out of the 25mm stock you could get what is a "common" hex size for the drawbars over here, 11/16", or 19mm, up to 21mm or perhaps 22mm. What you chose depends upon what size round shoulder fits down inside the spindle housing to "draw against", hopefully not much larger than 25mm. Leave about 6 to 8mm of diameter and mill the hex above that for whatever length of hex you want sticking up.
The length of the hex on the drawbars is debatable. I have a couple of drawbars for my machine and both are the 4" (100mm) long hex that allows you to change the tool without retracting the quill. I've yet to try it out of force of habit. Moreover, I'm perilously close to just chopping the excess length off the hex because there's a certain range within the quill travel that it just rattles around in the vari-speed housing and making a LOT of noise.
I know a lot of folks appreciate being able to change tools without raising the quill, I think I'll manage the old-fashioned way.