As others have said, it all depends ...

Many years ago I bought an optical center-punch - basically a gadget that
allows you to place a center punch mark exactly on a scribed line. For
something like this operation I would start at one end, scribe a line the
entire length. Then start with a cross mark at one end, center punch it,
then use that center punch with a pair of compasses to mark the next
crossing, etc. One down side of this method is that if the hole/hole spacing
is not exactly correct, then the end holes will be somewhat out of position.
If you need absolute accuracy (means that each hole must go in the correct
place +- some tolerance), then make all hole position measurements from one
end instead.

Drilling is just as important as marking. If the drill bit you use is larger
across the chisel end than the size of your center punch, the drill will
wander. Far better to use a proper center drill, whose end comes to a point
and therefore locates precisely in the center punch mark. Once you have a
center hole started, use an ordinary drill. If you cannot get accurate hole
positions even so, then bear in mind that a possible cause is poor quality
or badly sharpened drills.

If you want the sets of holes in the separate pieces of metal to line up,
clamp them together before drilling ... (or use one as a jig to line up the
other holes).

D

"Daven Thrice" wrote in message
news:mu81d.259560$sh.198210@fed1read06...
I have a piece of 1", 1/8" aluminum angle iron that is 18" long and 1/8"
thick. I want to drill sixteen holes in it, in a straight line, each hole
1"
away from the other. I also have a flat piece of aluminum that is 2" x 18"
x
1/8" thick. I want to drill two rows of 16 holes in that one. All holes
are
1/4" in diameter.

I've scrapped enough metal to set my ego aside and admit that I need help
with the very basics of basics. How do I make the measurements, mark them,
and then drill the holes?

Thanks!






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