$30 bit on first try

[909anchordown]

Greetings all. I just tried my first aluminum project. It roughly a 10" long x 3/4" wide control lever in 6061-T6 .125 thick with a row of adjustment holes. I fitted a new Onsrud single O 1/8" diameter upcut bit to my 2 HP spindle, and when the router started profiling the part after cutting the holes, the bit broke. Did I stress the bit by plunging .063 and cutting the .188 diameter holes? Settings were: 15000 rpm and .7 ips with .5 ips on the Z.
Right now I only have the PartWizard software that came with the PRT. I have just read up on the drill press app and it looks like that is what I need to do this spiral/helical ramp for the holes.
I have in the past only cut large foam parts so did not have to fuss much with feed rates, ramps, small holes and so forth.
Do I cut and paste the tool path code from that into a file with the profile code?
Anything else I should be doing? I have a powerful dust collector to provide some cooling.

[bleeth]

When cutting aluminum you need to ramp in and your z speed should be much lower. For a quarter inch bit I use .25/sec. A 1/8" bit should be even lower.
Dust suction won't provide much cooling. I'll lay out a bit of aluminum cutting fluid on the toolpath.
Hold down is critical. It doesn't take much movement of the part to blow your bit.

[rb99]

Is 15,000rpm too fast?

[MogulTx]

Probably should be less than 13.5K or so on speed. I use 1.39 IPS and .5 Z IPS. I use an Onsrud 62-606 on some of my aluminum work. I also set a spiral ramp into the cut that I want to make, and I also set the depth per pass at .02 or .03.

The 6061 is stout aluminum. Think of it as a hard material that you need to peel into slowly. Some people say you should use alcohol to cool the cutting. I use WD40 some times- but not all the time.

Basically: Cut shallow and move slow. If the bit starts heating it is either going too slow and heating the aluminum, or going to fast and heating the bit and stressing it. - Heating the aluminum means it will melt onto you bit. Heating the bit means it is moving too fast and will not be able to continue cutting the aluminum. It will get stressed and snap pretty quick. Take a shallower "bite" and keep after it!

Best of luck to you!

[rb99]

Alumi-cut works really well. The stuff I used was a thicker greeny blue liquid.

[bruce_taylor]

I'm no expert but I have learned to start out very conservative and go up from there. When cutting metal it is a very slow process 1/8 inch bits break very easily and will deflect quit a bit try to use as big as possible and I feel for your loss!

[909anchordown]

Thank you, all.

I based my set-up on forum posts that I understood to be similar to what I was doing. I understand the sneak up on the feeds and speeds concept. I did take pictures up close and saved the bit & some chips in case I get a chance to have an expert stop by. Question for MGM: Your Onsrud 62-606 is a down-cut and I thought that would invite issues with chips being forced into one another and melting. Do they clear out readily?