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?

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.

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

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? :p
Seriously though, what is a boring head? I've seen them in catalogs, but I don't know how they work...

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/attachment.php?attachmentid=644

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

You'll wish. :)

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.

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.

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.

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

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.

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.

Just finished drilling my 2nd 30mm hole with a forstner bit & thought I would share a pic. Aluminum 6061, 30mm dia. & 3/8" deep. I took it a little slower this time. It took me about 30 minutes to finish it but no smoking belts on the drill press this time :) So for those of us who are not a machinist, working with a minimal of tools, there is hope. Well, I guess we'll see if it actually works when I finish this thing.

It would probably help to have some of those Forstner bits that are carbide tipped.

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

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.

You guys mean something like one of these (http://www.ostartools.com/products/holesaws/adjustable/adjustable.htm)?

FWIW, the Silver and Deming set I got from Harbor Freight = Total Crap. They are the crappiest bunch of crap bits I have ever seen. Not even close to balanced, chatter like you wouldn't beleive. I tried drilling a hole with one through some spare MDF I had laying around - I thought it was going to rip the chuck off of my press. It was so bad I got about an 1/8" into the wood before I had to stop. So, I seriously doubt these would work for the aluminum that I have.

JavaDog....that is one ugly flycutter....but, yes that's the basic idea. I think the shield on the flycutter is kinda cute...

Have you looked into using a UniBit? I have used Unibits to punch 7/8" holes in thick plate before I got my mill and I seem to recall seeing a large (possibly 1" - 1.5") diameter step bit at HD or Lowes - it may have been at Fastenall...?

I think using a step drill would work well but driving power maybe an issue with a smaller drill press. If you were successful in getting the 1" hole in your plate, then you could bore it from there as previously suggested with an adjustable boring head.

Scott

Try a NEW spade bit, spend the $3, you will be surprised!

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

reduced dia shank. came up on another board recently and someone posted this link, everything and more than you ever wanted to know.

http://www.owwm.com/MfgIndex/detail.asp?ID=1017

I don't know why the drill didnt' work for you, obviously there are lots of reasons why a drill doesn't work properly, but nothing specific to the SD style except maybe its taking a bigger cut and you need to run slower with the bigger dia cutter, stil those are basic to cutting and not SD specific. machine not rigid enough? weak set up? to big a cut? dill not sharpened properly? running to quickly. all these can produce chatter when drilling

If you were successful in getting the 1" hole in your plate, then you could bore it from there as previously suggested with an adjustable boring head.

Scott

I haven't been able to find anyone local that sells boring heads. Guess I would have to order on online...

Try a NEW spade bit, spend the $3, you will be surprised!

I have sme new spade bits laying around, I am dubious, but I will give it a try on some scrap. :)

I don't know why the drill didnt' work for you, obviously there are lots of reasons why a drill doesn't work properly, but nothing specific to the SD style except maybe its taking a bigger cut and you need to run slower with the bigger dia cutter, stil those are basic to cutting and not SD specific. machine not rigid enough? weak set up? to big a cut? dill not sharpened properly? running to quickly. all these can produce chatter when drilling

I ran as slow as my press will go, and it still chatters like crazy. Even the lightest pressure and it just chatters and screams.

Could it be that the cheap HF 'Drill Master (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=527)' brand bits are junk?

javadog,

Try shorting the shank on the bit and most likly you will need lots of pressure to keep it from chatering. a 1 inch hole in one pass is a big bite. And is this spade drill at 180 deg. or 118,135 and does it have a pilot? Dont forget the lube.

Good luck

Hope this helps

I ran as slow as my press will go, and it still chatters like crazy. Even the lightest pressure and it just chatters and screams.

Could it be that the cheap HF 'Drill Master (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=527)' brand bits are junk?

Probably :D, but I bet that isn't the problem. I'll guess here cuz there's a lot of variables i dont' have info on..... its going too fast and/or too big a cut for the rigidity of the machine. for example, if the pilot is .25 and you are using 1" drill, this a .75 cut - pretty big for a drill pres, esp a light one. think of taking a cut like that on the mill or lathe. those machines are sturdier than a drill press and they'll (depending on size) chatter with a 3/4" cut. I suggestion openning it in stages and make things as rigid as can be.

how about an hole saw its rough but it will put a hole in the part with ease.

When you are using a big drill in a small drill press sometimes it is better to not use a pilot hole. This seems a bit counterintuitive but the reason is that with a pilot hole the big bit is only touching on the very sharp cutting edge so its digs in one side , catches, jumps out of that side and across and digs in again and you get a horrible mess. Without a pilot hole the center web of the big drill is really only forcing its way into the material, not cutting and this tends to keep the drill centered. It also gives a considerable amount of back pressure and prevents the drill digging in and taking too big of a cut.

If you are cutting steel this most likely will not work because you cannot get enough pressure to force the web into the material. With aluminum it is marginal; a really hard 7000 series alloy will be very difficult but 6061 should be possible with patience and lubrication. Also you can drill a very tiny pilot hole; something with a diameter about the thickness of the web on the big drill or slightly smaller.