Hmm, that is different from what I had been told previously.
I am willing to give it a try though.
Do you have a particular bit model you can recommend in
1/8 or 1/4 inch bit size.

http://www.amanatool.com/cncroutingd...bit-51402.html

A downcut will work on thin aluminum, IF you cut it in one pass. If cutting less than full depth, there's no place for the chips to go when the bit is pushing them down.

I was attempting to do the cut in one pass, but the bit did not penetrate all the they way. The material is 6061-T6 .025 thick. It took rerunning three times before the bit broke through. That is what was confusing.

I will give the 0-flute bits a try though. Do I do plunge with them for thin material or should I ramp in.

Have to ask one more question as well. What is a 0-flute bit. On the page you referenced, they show up cut and down cut versions. Now I am really confused! :)

Sorry, I didn't read the first post, as it was on the previous page.

For very thin material like that, a downcut bit will be better. An upcut will bend the edges up at the cut.

How deep into the spoilboard were you trying to cut. I'd go at least .01". If you try to barely cut through, it'll push the aluminum down as you noticed, and not go all the way through.

Always ramp if possible, regardless of material.

"O" flute is the shape of the flute (profile). You can get either up or downcut "o" flutes.

I was hoping someone with some experience would chime in. I'm learning as well.

I made two attempts. The first attempt was to cut right at .025 inch or .635mm
The second attempt, I increased the cut dept to 1mm. The second cut attempt was the one that took 3 passes to break through.

I will order the down cut 0-flute bit and give that a try with ramping. Will let you know how it goes after I test the bit.

Darren,
All this was a first test in being able to cut airplane parts. I did use my machine over the weekend to make some simple plywood spacing jigs for the main spar and a flanging die for the the lightening holes in the ribs. The cut test was just cutting some simple circles to test the die.

I appreciate you sharing this, DB.
I'm just geeky enough to find it intriguing.
I'd love to see the flanging die you made.

Is there some backlash in your Z axis? The Z axis was not going down to the correct depth, or it would have cut through.

Since I am using geared steppers, there is probably some backlash. If it is like the other axes, there is probably .25mm. I have not had any problems with wood cuts, but of course 6061-T6 is a little bit harder. Something to check.

As Ger said, Spiral-O bit with lubrication - Aluminium "welds" to the bit very easily so must be kept cool and lubricated.

Flanging Die
 

A pic of the plywood flanging die I cut over the weekend along with a test. This is for pressing flanges into lightening holes for wing ribs. The diameter is 51mm. The top die is two pieces of plywood stacked together after cutting. There is also a second bottom doughnut piece for additional height not shown.

I just did 2D cuts and used my lathe to bevel the edges to 45 degrees. I think the next one I make I will try the 3D cutting capability and see if I can get a die that does not require as much post processing.

I will need to cut a few steel backer plates. I almost broke the edge of the die while doing this test flange.

I have to make three more in larger sizes.

Instead of 3D that takes forever, I would use a V groove tool to do the bevel.

http://www.ebay.com/itm/1-PC-1-2-Sha...item20db905623

yes, 1 tool change & you are done.

That's a big V bit!

I would not do a full 3D profile cut. The plan for the next one be to do the usual flat cuts, then finish off with either a round nose bit or one of my smaller V bits.

Very Cool!!

He didn't mean to plunge a V-bit into the center. You just go around the circle to the depth of the bevel, either before or after you cut the center out.

Yes, that's it. But it's a huge V bit :), I put it as a sample and did not realize the size. It doubles my biggest one. on this kind of bits, the bigger can do the same as the small one plus can do a last clean pass if you need.

beware that huge bits often have a lower max rpm rating then you would think/your regular bits. Bit failure could get spectacular:D.

Is it spectacular if there's no one still around alive who saw it? Kinda like does a tree make a noise when it falls in the woods if no one is around to hear it? I had to dig a chunk of carbide out of my arm from a table saw once(what guards), they don't spin near as fast as a router bit.

I was being sarcastic.

Ps. Remember that it's not only the rpm that matters for comparing your sawblades and router bit teeth velocity.
The bigger the blade the faster the teeth will actually travel at the same rpm.

People think a windmill turns slow untill they get close and get hit by the tip of the blade.
For instance if a 10 foot diameter blade was spinning at 120 RPM it's blade tip speed would be
circle = pi * diameter
Circumference of windmill = 3.14 * 10ft = 31.4 feet of travel for blade trip around each revolution
So if blade is doing 120 revs a min it is 31.4 ft * 120 rpm = 3770 feet/min or 42.8 mph blade tip speed

Freaking math! ;) :D

What airplane is this for?

Welcome back Hurshy. Have not seen you in a while.
The plane is a Zenith 650B.

when I was making the Zenith CH750 I found that the flex of the aluminum made me charge the design to compensate for spring back, I also used body puddy to add strength. I eventually just cut them out of steel on the metal lathe. It really took a lot of torque to get the flange the way I was finally happy with. The 650 is a beautiful plane. You are not to far from the factory. Those guys are the best.

Not to brag, but I'm less than an hour from them... Been thinking about a field trip.
I love this plane stuff with a MM...

Hurshy,
I would like to build the flange dies out of steel, but I can not get access to any that is a large enough diameter.If worst comes to worst, I can cast aluminum. However, at least for the small die, I am pretty happy with the flange produced. I just need a steel backer plate to support the edge of the plywood so it does not break.
Zenith usually answers my questions, but sometimes I get the feeling I am just bothering them. They seem to be more interested in the people buying their kits. In spite of this, I think these plans are the best ones for my needs.

Darren,
I remember you mentioning that. I would say go for it as far as visiting the Zenith factory. They have an open house day every month or so. Once a year the Corvair college has their engine build there as well.


Spent most of the day today doing CAD work for the plane.You can see a pic of the current state of the cad work. I add things on as I need to get a better understanding of how things fit together before I start cutting metal.

Just finished doing layout for holes for the main spar doublers. Before I can even get the point of riveting the spar together I will have drilled a couple of thousand holes

Very Cool.

I toured Jet Aviation in Cahokia Il. a month or so ago. Saw a 737 being converted to a private jet, and a 5 axis MasterCam.....

I'm fascinated by all things aviation.

If you are into aviation documentaries as well I can highly recommend Wings of Russia.
You can find it on youtube. It is an 18 part Russian produced series on the history of Russian/Soviet aviation. It provides a different and interesting perspective compared to the usual America centric aviation documentaries. Saw a lot of old aviation footage that I had not seen anywhere else before.