Re: [CAD_CAM_EDM_DRO] Dumb question on the drilling of holes

alan@... wrote:

>Forgive me this seemingly dumb question, but how does a person "drill"
>accurately placed holes under CNC control without first center-punching
>them.
>
>

Center-punching holes seems to get me within .01" if I'm REAL careful!
By drilling a starting
hole with a center drill (like used on a lathe) and then drilling with
standard jobber's length
drills, I get down very close to the accuracy of the machine.

>I currently use a center drill to start the hole ( for deep holes ) or
>just mill the hole via G02/03 command for shallow ones.
>
>But it occurs to me that there's got to be a better way. Are "spotting
>drills" that better way ?
>
>

I'm not sure spotting drills do any better. A short, solid-carbide
drill will do about the best
possible. Jobber's length drills tend to drill triangular holes in thin
materials. milling larger
holes isthe best way, although slower by far than a twist drill. I use
small center drills even for
sheet aluminum. I just make sure the pilot drill is smaller than the
final hole will be. It seems
to help with the triangular hole problem, too.

If you need holes to line up, you can clamp both parts together and
drill them both at the same
time. No way the holes won't line up, then!

Jon