How to drill a 3/4" hole in metal?

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God I'm surprised only one guy told you the right answer... You use a "step bit", Home Depot has them, they are cone shaped and cut 1/16 or 1/8 inch per step, you stop pushing when you hit the 3/4 inch step. They cut very fast, clean, and round especially through aluminum, but set the drill slower for aluminum. They are not cheap bits but well worth the money for metal fabrication jobs.
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They probably didn't tell him to use a step bit drill for two reasons.
First they only go to 1/2 inch.
Second if you find a 3/4 inch step drill the depth of each land is less than 1/4 inch
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Think about it. He wants 3/4" holes. The largest step on the bit I referred to is 3/4". Also the bits are made at least as large as 1 3/8". I have several different sizes and varieties of these.....Paul
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On Mon, 3 Nov 2008 11:54:29 -0800, "catguy"

There is a error on the page. Read the details...Six Steps 3/16 - 1/2
Yet the bit has 9 lands and is titled 1/4'' - 3/4''
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You are correct. The page is in error. Here is a set of three with the correct description for all. The original link shows a 3/4" bit in spite of the error...Paul
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber‘616
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snipped-for-privacy@mucks.net wrote:

ERRRRRRR!!! Wrong! I have a one inch step bit in my drill case. It doesn't have a drill point. I have to drill a 1/2 inch hole first. Large step bits are very expensive and may only be available from supply houses that serve more of a professional clientele. I've been working in the field of fabrication (not the political kind) for many years so I know these things. I'm also a tool junkie. Google before you post. One example:
http://tinyurl.com/5sfgnc
TDD
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On Mon, 03 Nov 2008 14:55:58 -0600, The Daring Dufas

You are in error. All you have to do is follow the link that was refereed to in this thread and you can clearly see the error. Here's the link:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?ItemnumberD460
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snipped-for-privacy@mucks.net wrote:

I don't see how I was in error. The poster wrote that the bits only go to 1/2 inch. WRONG!
The poster wrote that a 3/4 inch bit will have lands of less than 1/4 inch. WRONG!
I have step bits in my tool box that have 1/2 steps. I own a half dozen of the Harbor Freight bits and I have used them to drill through 1/4 inch aluminum without a problem. The only thing I recommend is using a lubricant and low speed. I've been using step bits since the things hit the market around here in the 1970's. The first bits I bought were marketed by Unibit. My first bits lasted me 10 years before I broke any of them. The bits I own have 3/8 and 1/2 inch shanks.
TDD
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Your example won't work. It has a 5/8 shank
"Google before you post"
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snipped-for-privacy@mucks.net wrote:

It was just an example of a large bit. It can drill a large hole. My 3/4 step bits have a 3/8 shank and I have used them to drill 3/4" holes in 1/4 inch aluminum without a problem. Comprehend before you post.
TDD
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Oh I do comprehend. Drilling a 3/4 hole with a 3/8 shank through 1/4 aluminum could easily be a losing proposition.
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snipped-for-privacy@mucks.net wrote:

It's no problem, I use my 15 year old B&D 12 volt cordless drill and a touch of saw wax and it zips right through it. I've built a lot of aluminum store fronts and installed manual and automatic doors. I have designed and built numerous items out of thick aluminum plate and have no problem drilling holes. I do have a 1/2 Milwaukee Hole Shooter that will take your arm off if it gets hung and I only use it for step bits that have a 1/2 shank. There are times when I use my drill press for precision work but most of the time, the 3/8 cordless works just fine.
TDD
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wrote:

The step bits are expensive but I bought a set of 3 from Harbor Freight for $8.99. I am sure it's not as fancy as the $50.00 ones but for what I used it for they worked great.
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On Nov 3, 7:39 pm, snipped-for-privacy@mucks.net wrote:

First you argue that the bits do not exist, then you argue the link is incorrect, then you argue the shank size is wrong, then you argue the bits won't work
they exist & they work in standard sized drill chucks & they work in 1/4" alumimum with a 3/8" shank (even with 1/4" shank) aluminum is soft; even 6063-T6 BTDT
http://www.makita.com/en-us/Modules/Accessories/AccessoryDetails.aspx?ID=11037
so please stop saying it won't work / cannot be done........it can & easily.

Yeah, using the wrong tool, the wrong technique or the wrong operator.
Alternative method:
Drill a 3/4" hole in aluminum with a HSS paddle bit ...not the most beautiful result with a used bit but with a new $5 Irwin bit & lube it will be fine................DBTDT too
(back up the aluminum plate with a piece of plywood to save the paddle bit spurs)
cheers Bob
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on 1/4" aluminum, a typical Unibit(tm) isn't going to help. I have one in my desk drawer as I type this, I hauled it out and looked at it, and it won't do more than 1/16" in one pass and 1/8" from both sides. For a nicely finished hole, unless you have a 1/2" drill motor, a hole saw is your best choice. Choice #2 would be to buy a proper 1/2" drill and a 3/4" bit with a 1/2" shank (pref. w/ 3 flats) but that could easily run close to $200. Most bits that size start at $20-30 and go up from there for fancier coatings, etc. Of course depending on the definition of "several" that might be the way to go.
nate
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RickH wrote:

I use step bits all the time in aluminum. My only suggestion would be to use a lubricant. I use either a liquid lube made for aluminum or saw wax. A tube of saw wax looks sort of like a chap stick on steroids. I've used Tap Magic cutting fluids for years:
http://www.tapmagic.com /
Saw wax:
http://www.relton.com/cutfluid2003.html#stick
I stick my drill bit into the wax and the wax will melt from the heat generated by drilling which will lube the drill bit.
TDD
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On Mon, 03 Nov 2008 13:55:55 -0600, The Daring Dufas

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Walter R. wrote:

I myself have a set of twist drills by Silver and Demming that go up to an inch and have 1/2 inch shanks.
--
Claude Hopper :)

? ? ¥
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Claude Hopper wrote:

Actually Silver and Deming is simply the name for that type of reduced shank drill bit (that is, a bit with a 1/2" shank, 6" OAL, and 3" flutes) unless they are real antiques. I say the latter because I presume (without any proof) that they must have been originally made by a company of that name.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
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Claude Hopper wrote:

Cool, they were actually manufactured by Silver & Deming Manufacturing Co.? I have some Silver & Deming bits but not those produced by Silver & Deming Manufacturing Co.
TDD
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