If well-adhered copper is getting pulled off the board, the back-grind angle
of the drill's flutes is usually responsible. With larger drills, it is
common to remove the back "lip" by hand with a grinder to resolve this. With
small diameter drills, not so easy. You're better off buying some better
quality drills to work on your masterpieces. This back-grind shape is
characteristic of inexpensive drills. Avoid anything from a local hardware
store, or any that come on card or blister packs, such as Vermont drills &
the like. Cheap CHinese drills sometimes work out very well with glass
boards, because they are typically overhardened - bad for breakage with the
average user, but good for abrasive materials like paper & glass.

Another possible scenario is that of drill RPM being too low- this requires
that the drill be held to the workpiece long enough to generate sufficient
heat to burn the laminating adhesive that holds the Cu to the substrate.
This does happen frequently with circuit boards because the substrates used
do not conduct heat away from the cut, as is the case in metalworking.
effective and consistent PCB ios even more sensitive to the need for good
tools and correct practice.

Remember from last week's thread that with typical circuit board size holes
the RPM has to be way up there, with 1,000 to 1,500 RPM being a minimum in
most cases- up to thousands of RPM.

C

>
>
> The speed and cutting angle make a big difference in the
> effectiveness of
> drills.

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