TOPIC: Enlarging a hole in thick aluminum

I have new aluminum clamps for my merc that will make everything I'm doing easier. Only one problem - I have a 7/8 hole in the middle of the clamp that needs to go on a 1" (actually 0.9975) shaft.

What is the best way of enlarging a hole from 7/8" to 1" in your home shop? I understand I could take it to a machine shop and have it done, but time (and $!) is of the essence.

Thanks for any help, suggestions, and ideas!

Frank

A large twist drill will self center better than most other methods. Set up a 7/8" drill in your drill press to center the part. Clamp the part in place on the table. Switch to the 1" drill and have at it.

Not as good, but cheaper in large sizes sometimes, are the carbide masonry bits.

Don't try this without a drill press. You will likely end up with a nasty elliptical mess.

If you live in MN call me. I'll do it for you at my machine shop. Now, today, and for free. (Fiberglassics discount )

Thanks jepstr, but I live in eastern NY! Otherwise I would have been right over...

I have a good old floor mount drill press, and it's set at 240/250 rpm right now. I mostly use it for steel, but it is adjustable for rpm to the low 1000's. I don't know if I have a 7/8 bit, but I have other ways of finding center and clamping the clamps down.

Would a masonry bit work? They are cheaper and this is like a two time thing. One clamp, then the other. Done.

I use cutting oil for all my drilling and tapping work too.

Thanks for the help, I appreciate it.

Frank

frank you could maybe start the hole from each side with a step bit,then change to a i inch bit,just a thought.

Exactly my thinking John! I've got a big step drill that goes to more than an inch. That would get the hole centered, then I could clamp it down and drill with the 1" bit, very slowly, lots of cutting oil. Maybe get a 1" drill bit tomorrow.

Enjoy the weekend!

Frank

Frank,

I think slower might be better for this.

If you get it clamped/bolted down really really well, the masonry bit should work. All the modern, insert style drills we use in the industrial metal shop are spade type bits now-a-days.

Todd

Try a uni bit or step bit .

Step bit, 1" masonry bit, scrap piece of wood for stabilization, good old floor mount drill press going real slow, lots of cutting fluid, presto zippo, done. Didn't have to buy any new tools either, everything right in my shop. Couldn't really clamp it, but wood kept it plumb, and my son Gregg held both ends, no problems at all.

Thanks for the help guys, especially jepster! Masonry bit did the trick, and I would never had tried it without your suggestion.

Frank