[Milsurplus] Probably OT: Drill press runout question

[Mike Hanz]

On 4/28/2014 10:46 PM, hwhall at compuserve.com wrote:
> I need to drill some very small circuit board holes for a project, #64 drill size (.036 inch). My drill press chuck wouldn't grab a bit that small, so I got a mini chuck to fit into the press. The mini chuck shank is 1/4 inch. When I installed the mini chuck, the drill bit wandered in a circle, like a case of runout. Not like a bent bit, the whole length of the bit was moving around. But when I put a 1/16 inch bit into the drill press, there isn't any runout anymore.
>
> Thinking the mini chuck to be faulty, I looked around the workbench some more and found a hand drill that would grab the #64, and it ran true when I turned it, so I removed it and inserted it into the drill press. It had a 5/16 inch shank. This combination also showed wobble. But the drill press still will turn a small diameter drill bit without noticeable wobble.
>
> It's as if the wobble turns up only when the drill press chuck is made to hold a larger diameter, and goes away with the smallest diameters. Does that make any sense or suggest something that I should inspect or adjust?

It makes sense, and is simply a reflection of a very worn or very 
inexpensive drill chuck.  You should be able to chuck the smaller chuck 
into the larger one and still maintain less than .001"TIR.  I have 
several Albrecht chucks that I use in my 1/2" chuck on the milling 
machine, including one that will hold a .008" drill, and have no problem 
with concatenating any of them.  You are probably getting the runout 
with larger drill bits in your drill press chuck but never noticed it.  
What that does is to cause the drill bits to wear more rapidly on one of 
the two cutting edges.  You can certainly try the tape and sleeve 
approach if you're in a hurry, but to fix it right, I'd get a decent 
Jacobs chuck for your machine from Enco 
(http://www.use-enco.com/CGI/INPDFF?PMPAGE=480 ) or other machine tool 
dealer.  You get what you pay for in this area.

73,
Mike  KC4TOS