metal working

[Zach England]

I hope you will forgive an off-topic post. I have a question about metal working. I need to drill some holes of approx 1 inch and 3/4 inch in some metal--either mild steel or aluminum of maybe 1/16 thick. I am building some tube amps and I am hoping to make wood cabinets with a metal top plate to save a few hundred dollars over custom fabricated chassis.

I don't do metal work. My question is this:

Is there a bit I can put in my drill press to make holes in metal that are this large? If I need to I can buy a chassis punch or have it done at a local machine shop, but this is becoming a VERY expensive project and I am hoping to save some money where I can. Ideas?

Thanks.

[Dan Hintz]

Zach,

SMC now has a metalworking forum... just in case you weren't aware

As holes get larger, you may want to consider a fly cutter. This is a lopsided, adjustable diameter cutter, and they work beautifully in drill presses if you can select a low enough speed (few hundred rpm).

[Callan Campbell]

Buy yourself some hole saws in the sizes you need. Run the drill press at a very low speed for the steel, or somewhat faster for the aluminum. You drill a 1/4" hole in the center of where you need the larger hole, and use the 1/4" rod of the hole saw arbor to align/guide with that small hole. Some arbors are available with the 1/4" drill bit as the arbor center so you save a step. Just be careful not to flex the 1/4" bit sideways in the drill press since it will snap in half without much trouble at times.
You'll need to pop the metal disc that will end up inside the hole saw once you've drilled through the sheetmetal. Use a small screwdriver through the slots in the side of the hole saw to push it out. Some better arbors now have designs to help eject the waste disc from the inside of the hole saw. These are pretty neat, but I don't know if they work with the fairly small hole saws that you'll be using. Use a cutting oil for the steel when you're drilling it, and a different fluid for the aluminum as some cutting oils can discolor the surface of the alloy if they're not meant for the aluminum.
Google Tap Magic to see what types of fairly cheap cutting oils are out there for aluminum.

[Julian Tracy]

No question at all in terms of what tool to use - get a step drill bit. One bit will do from 1/4" upto 1" and will do it fast and just about burr free.

No need for a drill press, the step drills work great on cordless drills as well.

Should be able to find a step drill bit of that size for between $20-40. Or ask around to anyone you know that does a lot of electrical work - they'll have plenty of them sitting around and would lend them to you I'd think.

Here's a tip for cutting the metal if you do use aluminum: if you use 1/16" or equivalent - simply layout out the dimensions and use a razor blade and a hard rule to score the lines a couple times and you'll be able to bend and snap the sheet metal to the lines and get clean cuts. A little run over with a file will make the cut burr-free.

Good luck.

Julian

[Julian Tracy]

Just saw the other replies - be very careful of using holesaw's in drill presses regardless of rpms. They wobble so much, they'll cause the tapered chuck shaft to fall right out of the spindle.

This assumes the two-piece holesaws of course - the integral-arbor versions wouldn't have that issues.

But a hole saw in 1/16" sheet metal is a bad idea - it'll give rough ugly holes and may catch and ruin your panel.

Either use a Step bit or get a panel hole punch, though the Step bit's the better choice all-around.

JT

[Zach England]

Thanks, guys. I actually have a step drill. I don't know why I didn't think of that.

Mods, feel free to move this to the metal forum. Thanks again.

[John Coloccia]

Just saw the other replies - be very careful of using holesaw's in drill presses regardless of rpms. They wobble so much, they'll cause the tapered chuck shaft to fall right out of the spindle.

This assumes the two-piece holesaws of course - the integral-arbor versions wouldn't have that issues.

But a hole saw in 1/16" sheet metal is a bad idea - it'll give rough ugly holes and may catch and ruin your panel.

Either use a Step bit or get a panel hole punch, though the Step bit's the better choice all-around.

JT

Exactly. For 1/16", the step drill is a FINE choice and much cheaper than a 1" Greenlee panel punch...and if you're going to get a panel punch, do get a Greenlee.

[Jay Jeffery]

Tap Magic works great on steel, but working in a welding shop several years ago I developed a sensitivity to fumes it produces when it gets hot. So be careful if you use it a lot. For aluminum, we always used WD-40. It works at least as well, if not better than the Tap Magic specially formulated for Al. It certainly smells better and you probably already have a can of it. For the steel, a little cutting oil, even motor oil, will go a long ways.

[Joe Kieve]

Don't think anyone has mentioned this yet, but clamp your sheet metal down before drilling. Spinning sheet metal can give you a nasty cut.
Just my 2 cents.

joe

[Zach England]

Awesome. I am in business and I didn't even have to buy anything. I even have a bottle of cutting fluid from when I had to drill and tap holes in an aluminum plate for a router table I built once. I have no idea why I bought the step drill, but I am glad I did.

[Zach England]

Don't think anyone has mentioned this yet, but clamp your sheet metal down before drilling. Spinning sheet metal can give you a nasty cut.
Just my 2 cents.

joe

Thanks. I AM aware of this, but unfortunately I learned it from experience.

[Bob Wingard]

Definitely, the step drill is the tool of choice ... you can safely use it for this project with no need to clamp the stock - it doesn't grab like other bits will ... the best & cheapest cutting fluid for aluminum is simple kerosene, unless you want to go buy some Alumatap for one project.

[Greg R Bradley]

I assume since you are building a tube amp, you are talking about more than a hole or two. You are best served by a chassis punch. I don't think they are very expensive in the small sizes, but I'm basing that on the ones I've bought and the last one was probably purchased 25 years ago.

My set is on loan to the local EAA and you can imagine how many holes go in sheet metal when you are building an airplane.

[Callan Campbell]

Just saw the other replies - be very careful of using holesaw's in drill presses regardless of rpms. They wobble so much, they'll cause the tapered chuck shaft to fall right out of the spindle.

This assumes the two-piece holesaws of course - the integral-arbor versions wouldn't have that issues.

But a hole saw in 1/16" sheet metal is a bad idea - it'll give rough ugly holes and may catch and ruin your panel.

Either use a Step bit or get a panel hole punch, though the Step bit's the better choice all-around.

JT

While I too like step-drills, I've had zero problems using hole saws for making holes in sheet metal for year. Yes, you need to hold the metal down, for any drilling process to be safe. Maybe your runout issues are due to cheaper drill press tolerances or hole saws. I've not had that problem unless the drill presses was known to be worn , for any drilling done with it.
The burr left is dependent on several factors, I've seen dull step-drills leave them too.

[David G Baker]

Zach,
I drill small holes in my thin material, just big enough to fit the threaded part of a Greenlee hole punch. I have at least 10 different sizes and some are specifically designed to do exactly what you are trying to do. I have had bad luck when trying to drill large holes in thin material. There are several different shapes (square, rectangle, round with small slots included, etc) but they are not cheap and if you need them they are well worth the investment.