Paul Drahn wrote:

On 8/19/2011 2:17 AM, Tom Gardner wrote:
I have to make four identical 1/4" plates that have 15 holes. 11 of the
holes be countersunk for 1/4" socket-head countersunk screws that will
be used to mount fixture parts, 4 of the holes are for #10 SHCS for
mounting to the machine. These fixtures will hold wood blocks in a
machine. I need .005" difference between hole placement in the plates.
The plates are 8" x 6"

My question is: Can I stack all four plates, tack weld them together and
drill all four plates at once in the mill using the DRO to position the
plates and have the top plate and the bottom plate be within .005"? In
other words, will the drill wander more than .005"? I will use a
combined drill countersink to spot the holes then drill undersized, then
drill the 1/4" hole using all new drills.

Back up just a minute, Tom.

You wrote the plates are 8" x 6". that tells me right away they are not
all the same size, but may be varying by 1/16 to 1/8 inch each way. Are
they perfectly square?

If I was going to do what you are attempting, I would stack them and
clamp them on the mill table and sacrifice two of the 15 holes for roll
pins that are smaller than what you will eventually drill those holes
out to.

Then drill your holes and mill the stack to the ultimate size needed.

For what he is doing it doesn't sound like it matters whether the edges
are straight or square. It might look nicer if they were but it wouldn't
add anything useful.

-jim


Paul