Drilling a stack of 1/4" plates

I've been wondering the same thing, but with 5. I think I may be better off not having interchangeable parts. Sure would be nice to have one of those CNC machines, so one could machine them and it wouldn't matter if they got mixed up or flipped over.

SW

You can do that easily if the mill head is true. Not sure why you would spot the holes with combination drill countersink. or do you mean center drill?

Since you have to counterbore 11 of the 15 holes, it would seem that you might save more time using counterbores with built-in pilots (type of drill bits) and do each plate individually. With the counterbores done on the mill, the pilot holds could be finished off on a drill press (if necessary)

The Bridgeport is as perfect as any can be with very low hours, trammed to perfection. I guess it's worth some test holes.

Yes, a "Center Drill"! Us old people have had many arguments over the years about the official name of the tool. Had I typed "center drill" I certainly would have gotten flack from other old people.

I'd ream them; it shouldn't be necessary to tack them together if you have a decent set of clamps for your mill. Put them on top of a couple of cutoffs so that the drills and then the reamer can go all the way through. (or on top of a sacrificial piece of something softer than the parts.)

Have Fun! Rich

For only 5 plates, with a DRO, I'd just do them one at a time and eliminate the possibility of screwing up all 4 at once. Likely be just about as fast too.

If it was 40 or more it would be a good excuse to put an NC conversion on the mill.

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.

Paul

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

The only thing that matters is the relationship of the mounting holes to the holes that fixture parts mount to. The outside dimensions don't matter as long as I have a (x=0, y=0) point on which to base all the holes coordinates.