Adam Oke

Adam Oke

Well Known Member
I'm looking at different ways to make a nice straight cut. I am working on the rudder and cut all of the stiffeners with a bandsaw. I avoided the snips in case I bow them drastically. It would also take too long. I tried a dremel and random cutoff wheels that were in the case, but after wrecking a bunch of wheels, I gave up on that idea and used the bandsaw. This worked ok in this situation, but it is not perfectly straight.

I'm thinking a table saw or tile saw for the next project. I'm about to fabricate the R-717 space, and about to do some cuts on R-710...

...So what is everyone using for cutting angles, sheets, etc to make a perfectly straight edge? How many teeth for the blade? Educate me. :)
 
Adam,

My trick for a straight cut on angle is to cut with a band saw, leaving it just a tich long, then sand it to final length on the disk sander, using the fence to keep it absolutely square to the disk. You get it square, smooth, and to a perfect length all at once. Polish on the scotchbrite wheel to finish!

Paul
 
sheet metal shear

Hi Adam,

The best way to to make a straight cut is to use a sheet metal shear. They come in all sizes and when you make the cut there is no waste.

Our local EAA chapter has a 48 inch shear. Harbor Freight also sells bench top models. Once you use a good shear, you'll be spoiled.

Note: only good for use on sheets

Mike
 
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Metal shears are great, but beyond the reach of your average RV homebuilder. I would add only one thing to Paul's post, and that is to get a straight cut on a bandsaw, use a fence on the bandsaw. I normally use a couple of squeeze clamps to hold a piece of angle to the bandsaw table which I use as a fence. This gives me nice straight cuts with no bending of the work as you can get with hand snips.

You do NOT need a metal bandsaw (implies variable speed) to cut any aluminum you need to build an RV, a wood bandsaw (single speed) works fine. I initially used blades with a lot of teeth per inch to cut with, but found that it was slow and the work got very hot. Using less teeth per inch made things go much faster and no overheating (burning your fingers). I use a 1/4 wide blade with 10 teeth per inch. Because the bandsaw cut is straight, less material removal is required on the sander to clean up the cut, which saves time, sanding belts, and burned fingers (again). The cut line is only about a 32nd of an inch beyond the finish line for cleanup. The overall result is very straight, professional looking cuts with no teeth marks.

Good luck!
 
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Quality snips worked good for me. The cutting left barely visible teeth marks which I filed down and polished the edges. No warping at all.
 
A router with a carbide bit works well to make long straight cuts on Alum sheet.
Clamp a straight edge to the sheet and follow it with the router.

The router and piloted bit will also cut shapes by following a pattern, works great when you have a large number of like parts.
 
As noted above, I also used a bandsaw. for the funky angles on the stiffeners, I cut a piece of 1 x 1 wood to the proper angle (about 20 degrees as I recall). I then put the piece of angle on the cut face of the 1 x 1 and slid the 1 x 1 along a fence. Writes harder than it actually is.

greg
 
Bandsaw setup and technique (allowing for blade tooth pitch) as Paul stated and you'll get pretty straight cuts, never shear quality but then I can't imagine using a shear for stiffeners...fingers may be a tad close!! FWIW, none of my stiffener cuts are perfectly straight..but then I challenge you to tell me if you can see them:D The scotchbrite disk will hardly ever leave a nice perfect straight edge....you could break out that antique tools so many have forgotten....the file!:p
 
I cut the skins for my -6A using a die grinder & a piece of steel approximately 3/8" x 4" x 48" as the guide. The edges came out really nice.
 
mitre saw

I did the same thing Paul mentioned most of the time - bandsaw with metal blade, followed by the belt sander.

For thick angle stock, I'd also recommend a mitre saw with a metal cutting disc.
 
When I cut the stiffeners and other straight cuts on thin sheet metal or thin angle, I used a Stanley Utility knife with a new, sharp blade. I clamped the pieces in a vice using AL vice jaw protectors. Clamping the pieces in the jaw protectors at the correct angle, I would scribe the parts several times with the knife, using the straight edge of the protector as a guide. After 3-4 good swipes with the knife, I could then bend the part at the scribe mark and snap the parts to remove the material unneeded. Then a light shaping on a belt sander or sanding disc dressed them to finished condition. This really works fast as I was able to cut all the stiffeners for the empenage in about an hour. Don't ask where I got the jaw protectors. They were a prize at an EAA seminar years ago. Turns out they were invaluable. They are about 6" long AL angle with 1-1/2" flanges, 1/4" thick. There is a V groove on one flange for holding round or hex objects. They have magnet strips for holding to the vice.

Hope this helps,

Roberta
 
When cutting the stiffener angles I used our "office sheet metal shear" otherwise know as a paper sheer. One of those old things that has a 2' by 2' board grid with a long lever with a blade attached to cut sheets of paper. We had a couple laying around in the office that were never used (primarily used before computers were common) and I commandeered one for myself. It worked perfectly and very quickly.
 
I used a bench shear aka throatless shear to cut my stiffeners. Cut directly on the line. Clean it up with emery/sandpaper on a sanding block then the scotchbrite stack o'pads mounted in the drill press.
 
Paper cutter aka rib stiffener cutter

Harbor Freight has a couple models of paper cutters that work nice for shearing thin aluminum parts. Be very careful how you hold your parts in the shear. One slip and you may end up like Stein, making it even more difficult placing washers in those difficult to reach areas around ailerons and rudders. :) Sorry, I couldn't resist. :D
 
Jetcowboy said:
Harbor Freight has a couple models of paper cutters that work nice for shearing thin aluminum parts. Be very careful how you hold your parts in the shear. One slip and you may end up like Stein, making it even more difficult placing washers in those difficult to reach areas around ailerons and rudders. :) Sorry, I couldn't resist. :D
Click to expand...

Ha! Touch? my friend! :)

Believe me, no upside to lopping off a finger - other than good for tricks and light conversation!

Don't worry, I don't get mad....I even - I'll get you back sooner or later! ;)

Cheers,
Stein
 
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