What's the best method to drill 1" hole in alum?

It sounds like you may have a limited equipment budget, and perhaps only a drill press. If so I'd suggest trying a circle cutter in your drill press. Something like this one:

Make sure you clamp the workpiece down TIGHT, and use an appropriate cutting fluid.

You may have to regrind the cutting tool a little to get adequate clearance back of it's business end.

Don't push the spindle speed or the downfeed. This may not be the fastest way to make those holes, but it'll work.

You didn't say how accurate the holes have to be, but you should be able to hit the diameter within .005" with a few tries at adjusting the circle cutter. Experiment with some thin stock to get the hole diameter you want before you tackle the 1/2" thick stuff.

I've cut big holes through 3/4" thick aluminum with one of those gadgets.

Maybe someone else will have a better idea. You can get BIG drills with cut down shanks which could go in your drillpress chuck, but they aren't cheap and you'd probably need a few intermediate sizes to creep up to the final diameter if you are using a small drillpress.

Just my .02,

Jeff

I really really hope you learned your lesson taking metalworking advice from some idiot at Sears! If I were you I'd go back to *that same guy* and hand him the hole saw and demand your money back.

Then google groups on "hole saw". This is a very frequently asked question.

GWE

joelholio wrote:

||Got great advice on accurate cutting of alum stock from this group, so ||I'm gonna return to the source.... I want to cut 1" dia. holes in 1/2" ||alum stock. I bought a 1" hole saw from Sears as the guy there said it ||would to the trick - disaster followed, so I'm here for advice.... || ||For what it's worth I used the hole saw in a drill press and it took ||forever to cust about 1/4" into the alum and the hole saw ended up with ||teeth missing. || ||Thanks in advance! ||Joel

Texas Parts Guy

Well said.

Pah - hole saws !

Get a 1" drill bit with reduced shank end to be able to hold it in your drill chuck - or turn the end of one down in a lathe. Stick a 1/2" drill through first as a pilot hole and then bang the 1" one through. A few seconds per hole at worst. Kerosene as a lubricant if you want or just go slow and do it dry. A good sharp drill will last for several hundred holes.

I raid my local second hand engineering supply place every now and then, buy up a load of old shagged big drills, sharpen them, turn the ends down to fit my drill chucks and they do fine for the odd job.

joelholio wrote in news:Xns95748E713B70joelhliohotmailcom@66.75.162.201:

The one inch bit sounds like the answer - if I can find one that has a

1/2" shank!! No way to turn one down myself. Googling hole saws just gave me a lot of threads that didn't produce any better approach than what I was using - and hole saws suck - teeth clog and slow!

Thanks to all that responded.

Dave If it's not a well protected secret, where is your local 2nd hand engineering supplies place? I've had no luck finding anywhere like this. Martin

Or get a large unibit stepped drill bit. If you get the right size you can do through-holes in thick material and not just sheet. It'll be a bit you grab over and over in the future for other stuff.

Koz

How many holes are you making? If it is just a few:

I know everyone is going to jump all over this one, but I would use a paddle bit in a drill press. The bit is cheap, you will get a fairly precise hole with a decent finish. Drill half way from one side, turn over and finish the cut from the other. Irwin speed bores work quite well.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

Good point. Sometimes we all forget that just getting it done sometimes supercedes doing it by the book. Best thing is those spade bits are a dime a dozen at flea markets. Who cares if you mess em up. I suspect you could round off the normally square point with a file and use it as a round pilot to improve raggedness problems of the hole

Koz

I bought a set of drills with 1/2 inch shanks from Enco a few years ago, from 9/16" to 1" in 1/16" steps, so 8 drills. I can use them in my drill press or in a portable drill. Very useful.

Look at part number 301-1064, it is a 1/2" shank 1" drill. I think that will solve your problem for $6.29 plus shipping, or you can look for a set. Reduced shank drills are sometimes called Silver and Demming, for historical reasons.

Richard

joelholio wrote:

All agreed - just one additional note. Clamp the piece down *bloody tight*! (and/or slacken off belt tension)

Hand feeding a 1" drill into al is asking for a grab.

-- Jeff R. (been known to bend a 1" drill by ignoring above advice)

Joel What you need is a Rotabroach bit. These are absolutely the best for what you are trying to do. I've used my 1" size several times using a regular drill press. Try it, you'll never look back.

I'd make a boring tool type deal, braze a bit of carbon steel onto a 1/2" shaft (quench as soon as the brass solidifes so it stays hard, then temper as proper). Grind to size and shape. Drill (step drill if necessary) 1/2" pilot hole, pass boring bit through. Pilot will support bit as it passes, so you can use a drill press.

Other than that... a 1" drill bit (a lot more expensive than junk laying around, mind you :D ) would work nicely. Next to that, while you have a hole saw, use WD-40 and go slow, that's what I hear.

Tim

Look for "slugger" bits. I think you can run them in a 1/2" drill press. I've seen them the most in portable magnetic base drill "presses" (I've heard the term "mag drill" a few times) used for drilling holes in steel plate. The sluggers cut a disc out kinda like a hole saw but with more material being cut - at least that's based on the ones I've seen. The things are pretty cool. I did a quick Google and here are some pics for you:

others make them besides Jancy.

Alternatively - go find a Silver & Deming set (meaning big bits turned down to 1/2" shanks) or even just the one drill you need. For Pete's sake, use a drill press with these.

One inch is small, so I wouldn't recommend a trepanning bit - those are the circle cutters you see where you move a small hardened cutter back and forth on a beam equal to the radius of the cut. I guess you could - your call. Never ever, ever use these in a portable drill.

Last, if you get a good bimetal hole saw, it will work too. Don't get a cheap one - get a Milwaukee or something else that is rated for cutting metal as well. As others have noted, be sure to lube it. Kerosene or wax is what I've seen the most.

On all, be sure to use a drill press - not a hand drill, especially the trepanning tool.

H>Got great advice on accurate cutting of alum stock from this group, so

If you need some really smooth bores though, consider a 7/8" or 15/16" Bit instead of the 1". Then clamp in place a well made circle template, then use your Wood Router, base guide and a sharp Carbide Straight bit to run around the template.

Then you'll have a nice clean perfect hole without any ragged finish.

Chris L

Richard Ferguson wrote in news:U927d.650994$ snipped-for-privacy@bgtnsc04-news.ops.worldnet.att.net:

Awesome! That's what I'm looking for! Thanks!

"Lane" wrote in news: snipped-for-privacy@comcast.com:

That's what I started to do looking for after the first response to my original query. Went to their web site, found the local distributor, called same. Was told they had been bought buy Greenley or Greenly & he had no inventory but call so & so. Called so & so - they had none... From the web site, it looks like a cool solution though - now if I could just get my hands on one....

Thanks so much for responding!

Check out MSC -

and search for page 2463 There are small kits - but look at the top right. Or the kits down the page on the left for sheet metal. Arbors in the kits or the single one on top.

Mart> Joel