Forstner Bit for Drilling Aluminum?

[lbperry]

I am fabricating a dash out of 1/8" aluminum sheet for a car I'm building and need to drill a number of 1/2" holes for toggle switches in it. Standard 1/2" bits produce a pretty sloppy hole. How can I drill some nice precise holes for the switches? Something like a forstner bit does in wood. Any good ideas? Only idea I've been able to come up with is to predrill with a 1/8" bit and then take the hole out to 1/2" with a step bit.
Question #2 I'm using standard bimetal hole saws for the gauges. Is there come kind of lubricant I can use on the saw teeth so they won't clog so much?
Thanks for any input,

 

[bggrnchvy]

http://www.amazon.com/dp/B003LY4E0Y/?tag=atomicindus08-20

These work very well at putting clean holes in all manner of flat metallic sheets.

As for holesaws, putting a few small diameter holes the width of the kerf around it diameter help keep from recutting chips and with cleanout.

 

[damnifeyeknow]

I use WD 40 or beeswax, because I have them on hand.

If you have a machine to hold it (drill press, mill) you can make holes with end mills or router bits. You could drill the material to 7/16 then use a reamer to enlarge the hole to 1/2 inch but a step bit would probably be faster.

Clamp the material well. I use 1/2 ply or 1/4 hardboard to protect the aluminum from the clamps.

If you have a scrollsaw metal cutting blades are available.

 

[PAToyota]

I second Chevy’s suggestion of an annual cutter. If you only need the 1/2”∅ you’re probably looking at $20 to $30 for one depending on import or US made.

As Damned says, clamp well and use a drillpress or mill. It’ll be hard to get good results with a handheld drill. Like he says, I use what is on hand - paraffin, light oil, a dab of grease…

 

[volleyball]

There are hole punch tools. Don't get a 1/2" pipe punch.
You drill a smaller hole and put the bolt through and tighten

 

[PAToyota]

An 1/8” sheet is a bit thick to use a punch - and will likely deform the sheet.

 

[Rookie2]

uni-bit or hole punch.

 

[Bondo]

I am fabricating a dash out of 1/8" aluminum sheet for a car I'm building and need to drill a number of 1/2" holes for toggle switches in it. Standard 1/2" bits produce a pretty sloppy hole. How can I drill some nice precise holes for the switches? Something like a forstner bit does in wood. Any good ideas? Only idea I've been able to come up with is to predrill with a 1/8" bit and then take the hole out to 1/2" with a step bit.
Question #2 I'm using standard bimetal hole saws for the gauges. Is there come kind of lubricant I can use on the saw teeth so they won't clog so much?
Thanks for any input,

Ayuh,.... Ya can't beat Beeswax for lube cuttin' aluminum,....
Rub it on the cuttin' tool, whenever it gets warm/ hot,...

Keep some ice cubes on the panel yer cuttin' to draw the heat away for the cut,....
Helps keep the metal from meltin', 'n cloggin' the saw teeth,...

I'd think the forstner bit might dig in, bite, 'n shift the panel or bend it, donno, never tried it,...

 

[kerrynzl]

There are hole punch tools. Don't get a 1/2" pipe punch.
You drill a smaller hole and put the bolt through and tighten

Called a "knock-out-punch" in your part of the world.
[chassis punch elsewhere]

Well worth the investment, they do a neat job with no sratches from swarf

 

[astroracer]

I'll second the annular cutters. Doesn't get any better then this for clean, accurate hole drilling. Once you've used them it's tuff to use anything else.
I've done a lot of steel and aluminum with mine.

Mark

 

[EdT]

+1 on the unibit (step drill) for the 1/2" holes. If you're feeling frugal, I've found the HF ones fine for sheet metal either aluminum or steel. For the hole saws, I have found that putting a few ,say, 1/4" holes inboard of the cut, but intersecting the cut line. This gives the chips someplace to go and things move MUCH faster. Same trick applies if using hole saws in wood. I had to do a bunch of 1 1/8" holes in stair treads and elected to use a hole saw since I had one the right size and didn't want to buy a forstner bit. It was going real slow with the chip clearing. tried drilling a 3/8 hole inboard of the cut line and each hole took about 30 seconds. For the big holes for the gauges, run the drill as slow as you can or slower and use lots of lube as suggested above.

 

[ADSR]

I'd think the forstner bit might dig in, bite, 'n shift the panel or bend it, donno, never tried it,...

either have I, but this thread makes me want to try it

 

[jimbbski]

I have found that a step drill is the cheapest easiest way to make a hole in sheet metal or metal 1/8 inch thick or thinner. The key to getting a "round" hole with a normal drill bit is that the material thickness has to be greater then the flute angle height. If a drill breaks through the material before the part of the drill that is full diameter enters the hole you will not get a round hole.

 

[racingtadpole]

either have I, but this thread makes me want to try it

I just did...my advice based on what I saw is yes it is possible in a drill press, but its slow and the piece MUST be clamped solidly to the table. Don't attempt it with a hand held drill.

A unibit or step drill would be my weapon of choice.

 

[fnieto]

If you fabricate often, then you might benefit from investing in a set of annular cutters.
The finished hole will be flawless. Yes, you can use many methods to achieve a hole, but if you want a quick clean and precise hole, do what many have recommended.

 

[tarbellb]

As other have mentioned:

Cheap = Step bit

Expensive (better) = Annular

 

[lbperry]

Thanks for all the great replies. Can't spring for a full set of annular bits right now so I'm cruising the net for a good price on a single 1/2" one. From what I'm seeing most don't seem to come with a centering bit or spike to guide the hole. That would seem to require that the work be securely clamped down and my old drill press wants to start chattering when put in that kind of situation.
While I continue my search for the annular bit, I'll experiment on some scrap and see if I can come up with a good technique.
Thanks again for all the replies and ideas.

 

[Todd1803]

Another vote for a uni / step bit.
The HF 3 piece set has surprised me. Recently used one too cut several 7/16" holes in 3/16 steel plate. I expected the bit to only live through 3 or 4 holes, but it did the entire job and still going strong.

 

[volleyball]

I would check electronic/electrical supply house to get a single bit.

Here is what I was referring to.

 

[Beemer533]

I've been really impressed with the spiral step bits.. I have a set of these and they cut really nice holes.

http://www.amazon.com/dp/B0090IHBL4/?tag=atomicindus08-20

 

[awdblazer]

greenlee slugbuster
drill 1/4 inch with drill then punch out with slugbuster

 

[lbperry]

Forstner Bit for Drilling Aluminum? My Solution

After trying step bits on several holes in scrap, I decided to quit trying to drill holes that were as precise as a Forstner, and actually try to use a Forstner bit on the 1/8" aluminum sheet.
First, I drilled a small hole in the center of each hole to center the center spike of the Forstner. Then, using a drop of cutting oil on each side, I drilled half way through the 1/8" aluminum from one side, and then flipped it over and drilled it the rest of the way through, I got lazy on the last two holes and drilled it all from one side and it it left a little more burr than doing it the other way, but either way gave me pretty good holes. Touched them lightly with a countersink bit to get rid of the burrs and they're pretty nice.
Probably wouldn't want to use a Forstner on anything much thicker than 1/8"; I pretty much finished off a 1/2" Forstner bit that was already pretty well used. Just have to go buy a new $10 Forstner now.
I'd like to thank everybodys' ideas and comments. I got a lot of different ways to look at the problem things to consider the next time I run into a similar situation.
Thanks again.