Re: EMC and Drilling

Hi David,

The only flaw I can see in your suggestion is that, if you try holding the frames down by screws directly through holes in the
frames, there is every possibility that this itself may put the frames out of position - particularly as a close fitting screw
would require you to have drilled the hole for it with great accuracy. The more normal way to do such a job would be to make a
low frame or set of 'stops' which would surround the frames and hold them laterally and then to have just one or two hold-downs
which could be either small bolts with big washers through oversize holes or perhaps 'dogs' in the 'wheel arches'. You would
then set the machine up to the jig without a part in place, i.e. set the jig on the table so that the top edge of the plate is
truly parallel to the 'x' axis etc., by holding a dial gauge in the chuck and running it along the inside edge of the jig as you
move the table under the spindle. The other essential is to make sure your drill is going to clear all the fixtures as it moves
from one hole to the next by using a 'reference plane' in the 'z' axis which is a predefined height that you lift the drill to
before every lateral move.

Ian

David L Anderson wrote:

> I want to drill holes at very precise (+/- .002) locations in 3/16"
> thick steel locomotive frames. To get the two frames to align to one
> another I stack them ( with small screws to hold them together) before I
> drill. This makes both sides identical even if I am off a bit. What I
> was thinking of was an aluminum tooling plate that I could fasten the
> "blanks" too with cap screws.