PCB drilling - Both sides?

[goaran]

Hello,

i have a general question on PCB drilling.
when i generate gcode for drilling with eagle-cad and the pcbtogcode plugin i get two drilling files, one for top, one for button.
Does it make sense to drill both sides and meet the holes in the middle of the board for better edges? When i drill them just from one side the copper stands off at the botton side. or should i just play around with the spindel-speed and feddrate

[Bubba]

I read somewhere that a person uses a vacuum chuck to hold his board. He drills one side about half way through and then covers it with self adhesive shelf paper and flips it over and drills the rest of the way through. The paper allows the vacuum chuck to hold the work without leaking.

[kn6za]

I think I am the one bubba is speaking of. I use a vac system and I drill holes from both sides of the board and meet half way though the board. Actually I drill past center from both sides. I can tell you this, your holes and traces always look perfectly aligned this way, but if there is any error the hole will be smaller than the drill by the amount your off target.

It has been working well for me, but it sounds like your drill bit is dull and you might remedy the problem with a sharp drill rather than going to the extra effort of drilling from both sides.

My tooling allows me to change tools without needing to measure the length each time so this helps make the process i use less frustrating.

[Bubba]

Andrew,
Yep, I remember that now that you expressed it. Matter of fact, I patterned my vacuum chuck after yours!

Thanks for your help.

[chuck99z28]

Same here.
Vacuum table, drill from both sides.
It seems easier on the drill bits and doesn't mar the table.

The larger bits, above 0.935 or so, would need to drill past the other side pretty far to compensate for the taper on the drill.

Plus, there are no burrs or anything left when you drill from both sides.

I copper plate all through holes also. Even when they don't need it. Because I like the bond/contact from the solder sucking into the holes. Soldering plated holes is ten times easier then non-plated and takes less heat to get the solder joint correct.

I also try to use surface mount as much as possible so there really aren't all that many holes to drill and plate. I prefer surface mount because soldering is a dream. Stick the components to the pads with solder paste, toss the board into a overn and presto, a soldered board.