.125 bit for alunimum

[brian]

A customer wants a .25 alunimum sign cut.
I will be toolpathing on the inside of the vectors and removing the waste.
Due to the small font used I need to use a .125 bit
I've used larger 0flutes before on alunimum but not a .125 bit.
What kind of speeds and feeds should I use for this.
And is this small of an 0flute the best choice.
I generally use Centurian bits

Thanks Brian

[Brady Watson]

Harvey Tool & Onsrud both have 1/8" spiral-O bits suitable for this. I stock O-flutes down to 1/16" for these types of jobs (Onsrud from Ballew Tool (http://www.ballewsawandtool.com) I think...) - Cutting edge length is probably going to be the limiting factor on tools smaller than 1/8". I think CEL on the ones I have are around 1/4" max.

For speeds & feeds...with a 1/16" tool I run 13-15k RPM @ .7,.5 IPS - watch those step down distances - I run around .01-.02 max depending on alloy. Those 1/16" ones are like a curled cat whisker...not a whole lot to them!

On an 1/8" tool, you can get away with more by means of speed. I'd still limit the step down to around .03" or so to keep the tool intact. One thing I found when cutting dense materials, like AL & brass - you really want to use the shortest tool possible to get the job done with little extra on the cutting length. This keeps the tool stiff and minimizes the tendency to snap on direction changes. This is really the idea when cutting anything on your CNC, but most critical in metals.

One thing you might consider is a 3/16" single flute spiral-O made for cutting AL. It only makes the radius a little bit bigger than the 1/8" bit would, but it is a LOT stiffer. I love the 3/16" size for doing 1/4" holes (inside profile cuts with spiral ramp) - and I have cut AL up to 1/2" thick with one. A really nice tool. You can get them with a 1/4" shank, which is nice because everyone has a 1/4" collet regardless of router or spindle.

Hope that helps! You might want to run some simulations in software to see the difference between the 1/8 & 3/16" to see if you can get away with it.

-B

[brian]

Thanks Brady
I need the .125 to fit inside the small letters

Brian

[coryatjohn]

I bought a set of 6 63-862E Onsrud 3mm O Flute bits for $13 (on sale) that have served me well for fine cutting aluminum.

[knight_toolworks]

when taking off so little in a pass you can get away with a regular upcut endmill or one designed for aluminum. but msot of the time you are limited to about .01 in a pass. but thats about the limit anyway of the smaller bits so it is not as big of a deal.