Looks like punched hole?

Well, I mill all my larger holes on a CNC milling machine, using a 4-flute end mill. The ID of the holes look like glass. Of course, if you don't have a CNC mill, that't a pretty expensive way to drill one hole.

Actually, if you have a decent drill press, you could try a 3/16"

Jon

Brad-point drills will drill aluminum and their point geometry lends to sheet metal. They're usually pretty cheap.

Regards,

Robin

I'll be darn, it payed to ask.

I have plenty of brad points so I'll try those but Jon, I was wondering if you could do me a favor.

At their site....

I didn't see anything that referenced to "center cutting".

Sounds like fun to try these out....I do have a nice shopsmith drill with vari-speed. (the lower rpm the better to start?)

THANKS guys.

Drill and ream to final ID

A regular spiral router bit will do just fine in aluminum. If you have a plung router even better but you can use them in a drill

They probably all are center-cutting. As long as they don't have a hole for a lathe center in the middle of the end, then they are center cutting.

You can also get two flute, which will work just as well. Anyway, the first group "square end" are what you want. Don't get any fancy coatings, solid carbide or any of that for this use. You just want the most basic version. But, that usually comes with a 3/8" shank, so you can't run those in a router. Which is good, because you can't hold a router steady enough with these. A good, solid drill press, and solidly clamped workpieces will do.

Jon

Thanks Jon...I'll order a variety from Mcarr. (love that place...have everything and in Indiana you see it in one day).

I tried the brad point this morning and that was pretty impressive also...I deburred the outgoing side with my step drill but the incoming side was a perfect circle.

Here I thought I was stupid to ask in the first place.

Live and learn.