Cutting Rectangular Hole in Aluminum Sheet?

[lbperry]

I need to cut a 3" x 4" rectangular hole in a piece of .120" aluminum sheet for a dash in a car I'm building. Since it'll be visible, I'd like to do a nice, neat job.
I've drilled 1/2" holes in the corners so that the hole will match the shape of the component to be mounted; but cutting the actual lines connecting the holes and doing a good job of it has me concerned.
I guess my attempt would be to heavily scribe a line where the cuts need to go and then clamp a piece of steel along the scribe line and doing the actual cutting with a dremel tool. Then dressing the cut with files, sandpaper, etc.
My main questions are:
Is there some kind of hand tool that I can use to deeply scribe the lines? I usually use just an awl for scribing but that's just scratching the surface. Aluminum is soft enough that it would seem that it shouldn't be to hard to deep scribe it with the right tool.
Is there a better technique than the dremel along a steel straight edge to do the cut? My saber saw has never been accurate enough to use it and I can't think of any tool I've got that will do a good job.
Any help or suggestions would be appreciated,
Thanks

 

[RXtacy]

Jigsaw with appropriate metal blade, then clean with file and debur.

 

[kd3pc]

small handheld nibbler would work. Electric/air shears. Sharp utility knife with sold backing and something to hold the work - while you carefully cut the panel.

nibbler would be cheapest, easiest and still provide a decent look.

http://www.amazon.com/dp/B000T5FV4Q/?tag=atomicindus08-20

 

[kazlx]

Jigsaw with aluminum blade will go right through that. Just cut a hair small and file to the line.

 

[astroracer]

If you back the cut line up with a piece of steel you don't need a "scribe line". Just set your backing up about a 1/16th of an inch inside your cut so you have some material left to sweeten up.
Mark

 

[UncleJoe]

I am not sure about the best way to do this but if you can catch up them fellars that escaped from that prison they seem to know all about cutting square holes in steel. Maybe if they are members here they could chime in and show us how it is done.

 

[gungatim]

instead of an awl, hit up HF and get their cheapo carbide scribe. it's a POS compared to a good scribe, but it is hard enough it won't wear down or scratch around like an awl. I just used it last night to make a block off plate from .125 aluminum on a manifold as a matter of fact!

 

[zkling]

Jig saw and then touch up with a file, or if you don't trust yourself with a power tool here, I'd used a coping saw for more control. That way if it ever drifts off you can control and correct it stroke by stroke.

 

[1wook]

Got a router? They work great for cutting aluminum. Make a wood pattern, double stick tape it to the aluminum and cut it out.

You can also use it for thick aluminum cuts too.

 

[mrvm]

I am not sure about the best way to do this but if you can catch up them fellars that escaped from that prison they seem to know all about cutting square holes in steel. Maybe if they are members here they could chime in and show us how it is done.

I'm actually impressed with the skill of their pipe cutting technique. Looks nice and straight with hardly any jagged lines to snag clothing or skin. Usually the noise from my tools would have waken the dead but maybe they used advanced hand held phasers to cut them lines.

 

[MoonRise]

small handheld nibbler would work. Electric/air shears. Sharp utility knife with sold backing and something to hold the work - while you carefully cut the panel.

nibbler would be cheapest, easiest and still provide a decent look.

http://www.amazon.com/dp/B000T5FV4Q/?tag=atomicindus08-20

I wouldn't want to try and cut through a piece of 0.120" thick aluminum with a utility knife.

Sheet metal thickness aluminum with a utility knife? Sure.

Jigsaw with aluminum blade will go right through that. Just cut a hair small and file to the line.

This. A decent jigsaw with a decent metal-cutting blade should make relatively quick work of that.

 

[ilovevocs]

I like to keep a small piece of extruded polystyrene around to do jigsaw work like this. I just throw the aluminum on top and cut away. Makes it allot easier than trying to cut over the edge of the table or supporting it on opposing sides of the cut since the material has such a small cross section and lacks rigidity.

 

[theoldwizard1]

Got a router? They work great for cutting aluminum. Make a wood pattern, double stick tape it to the aluminum and cut it out.

You can also use it for thick aluminum cuts too.

THIS is probably the best solution !

Carbide bit or steel bit ?

 

[dr_clyde]

I would use a jig saw and a file, myself. A router wont give you square corners.

 

[HammerMechanic]

I would use a jig saw and a file, myself. A router wont give you square corners.

Thats true, but it sounds like he wants the 1/4 Radius in the corners.

 

[rustyjames]

A jig saw will do that in no time, that's definitely the way I would go about it.

 

[fnieto]

A jig saw works great for this application. I use blue painters tape to protect the aluminum and it also works to layout the lines to follow the cut.

 

[dr_clyde]

Didn't read real close, apparently. If radiused corners, I'd still use a jigsaw and file since he's got the corners already drilled.

 

[Vegaman_Dan]

Doublesided carpet tape the metal to some plywood to give enough mass and tooth for the saw (rotary or saber/jig) to work with. Much less chance of the blade catching and tearing up the metal if it is supported like that.

Nibbler works great for the corners.

Cut up close to your scribed lines, use a long file to finish the opening to size.

 

[theoldwizard1]

Doublesided carpet tape the metal to some plywood to give enough mass and tooth for the saw (rotary or saber/jig) to work with. Much less chance of the blade catching and tearing up the metal if it is supported like that.

Great suggestion !

 

[Tucko]

Jigsaw with appropriate metal blade, then clean with file and debur.

Yes to the above. Also, use masking tape to prevent the aluminum from getting scratched up from the bottom of the saw.

 

[wyo george]

Got a router? They work great for cutting aluminum. Make a wood pattern, double stick tape it to the aluminum and cut it out.

You can also use it for thick aluminum cuts too.

This is how I would do it, I've used this method a few times over the years.

 

[gungatim]

THIS is probably the best solution !

Carbide bit or steel bit ?

carbide. you can cut aluminum on table saw or chop saw as well just use good carbide and go slow.

 

[astroracer]

I use the router for aluminum also. I have a speed controller. It lets me dial in the right speed and I can use HSS bits.
Cutting out electric fan clearance holes in a radiator shroud.

Mark

 

[RXtacy]

I use the router for aluminum also. I have a speed controller. It lets me dial in the right speed and I can use HSS bits.
Cutting out electric fan clearance holes in a radiator shroud.
http://images108.fotki.com/v613/photos/5/904975/11267914/MVC009F-vi.jpg[img]
Mark[/QUOTE]

Were you using a standard double flute straight cut router bit, or an end mill, or something else?

 

[ez-duzit]

Fastest way is with a saber saw. Then use a vixen file to smooth the cuts. A router using a small diameter carbide bit and a plywood template would do it, too.

 

[lbperry]

Thanks for all the replies. Some good ideas. I agree that a jig saw would probably be the best approach; but mine never has cut a good straight line. Probably operator error. I'll try one of the other suggestions and see how it works out.
Thanks,

 

[ilovevocs]

If using a jig saw it helps to have a unit where the oscillation of the blade is adjustable. I turn it all the way off. Makes for a cleaner more controlled cut.

 

[lbperry]

Not a bad idea, ilovevocs. I'll have to give it a try.
Thanks

 

[1wook]

I use two flute carbide bits in my router. HSS works too.

For long straight cuts I use my skill saw with a higher tooth count carbide blade. Leaves a nicer edge than my plasma.