Drilling Holes in Aluminum

[JavaDog]

Hey all,
I have my 10" Delta drill press and a decent set of HSS bits that go up to 1/4". However, now I need to drill some 1" and 2" size holes in some 1/4" 6061 plate.

I bought a set of Harbor Freight el-cheapo-chinese forstner bits for a project (the Underwater ROV). They worked great for the plastic I was milling, but they have a million warning not to use them on metal.

So, how does one go about making larger round holes in Alum. when they only have a drill press?

[psychomill]

In 1/4" you might be able to get away with buying whats called a "S&D" drill (Silver and Deming). For a 1", it should fit your chuck. You don't have a lot of power so just take it easy on it. I've drilled 1" + sized holes on a cheaper and smaller drill press and got by with it.

The 2" hole is tough for trying to drill though. Instead, I use a hole saw. You're only going through 1/4 plate so it should be no problem. Just peck at it with some cutting fluid brushed on.

[ViperTX]

Well you could use a bi-metal hole saw, or you could chuck up a boring head on your drill press.

[JavaDog]

In 1/4" you might be able to get away with buying whats called a "S&D" drill (Silver and Deming). For a 1", it should fit your chuck. You don't have a lot of power so just take it easy on it. I've drilled 1" + sized holes on a cheaper and smaller drill press and got by with it.

The 2" hole is tough for trying to drill though. Instead, I use a hole saw. You're only going through 1/4 plate so it should be no problem. Just peck at it with some cutting fluid brushed on.

I've seen the Silver and Deming sets...what exactly are they that differs from normal drill bits?

Holes saws tend to make really sloppy holes though - but that why there is sandpaper! I know I have a decent set in that size...

Well you could use a bi-metal hole saw, or you could chuck up a boring head on your drill press.

Boring head? Isn't that what happens after you get married?
Seriously though, what is a boring head? I've seen them in catalogs, but I don't know how they work...

[ger21]

Drill the holes in MDF with the forstner bits. Use a hole saw about 1/8" smaller than the finished hole size to rough out the hole. Clamp the mdf into position and use a router (slowly) with a pattern bit to clean up the hole. It's a bit hard to see, but that's how I did the holes in these plates. http://www.cnczone.com/forums/attach...tachmentid=644

[ger21]

Boring head? Isn't that what happens after you get married?

You'll wish.

[beausdn]

I know this sounds stupid but it works really well. Spade bits (yes the cheap ones) work very well . I didn't believe it either but was amazed at how well they work , I've drilled a 50mm hole through 5/8 6061 Aluminum And it looks great (although I didn't mic it) it was a 2" spade bit that I ground down in a drill press to get it down to 50mm.

[Thoob]

Maybe Im a little new aged but my suggestion would be to bring it to a shop that has bigger machines and ask them to drill out the hole for you? Would probably cost you less then what it would for a new tool and save you the headache.

[Al_The_Man]

Do they have to be spot on 1" & 2"? Because if you know an industrial electrician, ask him if you can use his greenlee slug-buster, this is a panel punch for conduit holes in electrical panels, this makes a quick clean hole, although you can get 1" & 2" exactly, most electricians have the conduit sizes which are slightly under and slightly over those dimensions.
Al.

[MILLMANM]

how about an adjustable hole cutter
it uses a hss bit and a 1/4 bit for a pilot , have used in the past
and it worked well
just a thought

[ViperTX]

MILMANM's suggestion is to use a flycutter....they are kinda hard to find these days, but you can find them. If you were so inclined you could make your own.

[dfranks]

I have used a spade bit as well, drilling up to 1 1/4" diameter, for making my bearing mounting blocks. I had to take it slow and just kept spraying it with WD40 (didn't have an real cutting oil) as I am using a cheapie drill press but it got the job done and it turned out surprisingly well. I have also used a 30mm forstner bit but that is really had on my drill press, the pulley belts were smoking by the time I got done. Thank goodness I only have one more of those to drill.