I need to make a draw bar for a garage sale piece of equipment I picked up cheap recently. Its got a drill chuck and a metric draw bar, but it won't work for the collet holder I want to use instead of the chuck. The collet holder has the right taper, but uses a 3/8 draw bar. There is only about
1/4 or maybe 5/16 passage through the spindle for the draw bar.I figured to get a piece of rod, thread both ends with some standard threads, and make a theaded bushing to loctite onto one end to go in the collet chuck. Then make a knob to go on the other end to make it easy to loosen if I ever want to take the collet chuck out. Something easy to hit with a hammer instead of slipping of and smacking a pulley.
(The draw bar holding the drill chuck taper was similarly configured except metric and just had a nut.)
I can't think of any reason to get overly obsessive compulsive over it, but I thought I'ld ask you guys if there was any reason I needed to go ape over balancing it or getting my bushing highly accurately concentric? This machine spindle is relatively low speed. Top speed is 3840, but I don't see me using it at that speed very often. I just plan to use it for the occassional manual milling operation that I can do faster by hand than to write a snip of code for one of the CNC machines, or for when I have a project going on the machines, and have something else I want to try.
With it basically going through the axis of rotation it would take a pretty significant imbalance I am thinking to cause any vibration. That and it doesn't have anything holding it EXACTLY centered at the top end anyway. I suppose I could make the knob with a slight taper to do that if I wanted to, but I think I would rather have a flat washer in between to protect the surfaces. Speaking of washers, Since the taper is actually holding the chuck. Any reason to need a spring washer under the knob?