Homebrew PCBs

On Fri, 10 Jun 2005 21:31:38 +0200, Bob & Linda Gardner  
<gardner.bob@...> wrote:

> Stefan,
> For a drill bit size chart try:
> <http://drillbitcity.com/images/charts/drill_bit_comp_chart.pdf>
> Bob


Thanks, that's what i needed. Thanks als for the other offers.

As for moving the rings, i will still try a hammer, because i'm pigheaded  
;-)
When i  have broken a bit i will perhaps make a jig that can be used in a  
vice or something. I only see how to move the ring in one way, anyway, i  
gueess one must start all over if one moved it too far.


Thinking about it, a simple mechanism with a screw would be easy to make.  
take a piece of tubing, just bigger than the ring, and either cut a  
screwthread inside it or braze a nut to it. on the other end mount a  
washer that has a inner diameter smaller than the plastic ring outer  
diameter. you slip the tubing piece over the bit from the front, so that  
the washer sits against the ring, and then simply screw the screw in to  
pull the ring back on the shaft, the screw pressing against the end of the  
drill. should allow precise adjustment, just add wings to screw and tube  
for easy turning by hand. theoretically one might be able to drill out the  
screw to allow pressure from the other side also, but probably it would  
cause beaking of the drill if all is not straight. Probably it is easier  
to make two screwsm one with a flat or slightly depressed end to normally  
push the shaft along, and one with a stud slightly smaller than a drill  
shaft, to press the ring all the way off (of one has moved it too far or  
it must go on another bit).


Varitions to this design could be contemplated, like allowing to insert  
the drill from the side so it isn't necessary to take the tool apart  
completely, but it would be more difficult to make.


Now i wonder what professional bit grinding shops or manufacturers use?


ST