Router RPM for cutting out rib blanks

[N3UW]

I am using a router to cut out the rib blanks for my patrol. I am currently using a Delta table top router/shaper (Delta 43-505) that I have had around the shop for a while. It spins at 12,500 RPM. I am using a combination of 1/4" and 1/2" solid carbide spiral bits and 1/2" 2 flute carbide bits. I seem to be getting a fair amount of chattering from the bit. I have a few heavy duty variable speed 1/2" routers and have been thinking of building a router table to see if changing the speed helps. What have you guys discovered? Have you had problems with bits chattering? What speed have you used? Any suggestions.

BTW, I have been using my rubber pad press technique to form the aileron nose ribs. While my press is not powerful to press the wing nose ribs, it does great for the aileron ribs. I also taper the form blocks that I use 10deg to deal with the spring back. I press them in about 20 seconds and pull them off the form block and the flanges are right at 90deg. No adjustment needed. Only wish I had a 100-200 ton press and I could form the ribs also. I also lubricate the blanks a bit with Pledge to allow the rubber to slide.

[DRLPatrol]

That is great. How about some detailed pictures of the rubber pad forming process.
Doug

[bestbearhawk1231]

When I cut out the rib blanks for my 4 place, I had better luck with the 3 flute bits for cutting laminate. The 2 blades would chatter. I was using a cheap single speed 1/4" Ryobi router/ table combination. I can't tell you what the differences between 1/4 and 1/2 inch would be on metal, but on wood I have always had better luck with the 1/2" bits. Keep the bearing well lubricated, I used mobile one synthetic motor oil. After I routed a set of 5 blanks I would put a couple drops of oil on the bearing and coat the bit with Boelube. The bits started lasting quite a bit longer after I started doing that. If the bearing over heats and locks up, it will destroy your cutting form block before you realize what happened. The bits get hot fast cutting aluminum and the heat goes strait to the bearing.

Oh ya, watch the lightening holes when you route them out, the little disks fly out with force. I left a little tab to hold the disk in place and finished up with a little snip of the tin snips.

[X'N]

Try using your drill press as fast as it will go. You never said how many flutes your router bits are. It makes a difference. Single flute you should be fine around that rpm, 2 or 3 flute that is way too fast. Also the thinner the cut the better they will cut. If your bearing is changeable you may want to throw on a bigger bearing for the roughing pass and then switch to the correct bearing for the finish pass.

[Glenn Patterson]

Basically the same as Dan. I found that if I routered 1 or 2 ribs at a time that the cutter marks were very fine and very easy to sand out. If I went with 4 blanks then the chatter marks were a lot heavier & took more time to remove. The time spent cutting the blanks 1 or 2 at a time saves time on the edge polishing. Piling the aluminum layers up makes for very dry & sticky cutting.
Glenn