Milling brass with 3mm end mill

[Memran]

Three cutters later, its time to get some help!

I am trying to cut a profile in 2mm brass sheet, with a 3mm end mill, but I am clearly doing it wrong. There is a raised area around the toolpath, as if the brass is being pushed up out of the way instead of being cut.

My cutting parameters, with mist coolant:
2000rpm, 200mm/min, 0.5mm doc -> snap!
2000rpm, 100mm/min, 0.5mm doc -> snap!

I'm running out of end mills, so can you help me get this right please?

[aarggh]

I have a feeling brass is one of those materials that work hardens. You may need to take shallower cuts to allow for your mills power rate, but at a faster feedrate. I'm sure other more experienced members will have more qualified opinions.

Cheers,
Ian

[graham scott]

Are you sure you are not using "Yellow" brass, this is soft and at 2mm would be bendable. Purchased in sheet form. Unlike Hard brass, purcahsed in bar form which is machine very easily, by mill or lathe.

Yellow brass can be stamped and bent simmilar to Aluiminuim, it dosen't like being machined with small cutters as it has a long structure and is soft, therefore the material will be "pushed" by the cutter, overloading it and breakage will occur.

If this is the case very light fast cut cuts with a sharp single flute cutter should work, using flood coolant.

Graham

[Memran]

Thanks for your help

Yes from what you say, I think it is very likely yellow brass.
The cutters I was breaking were 4 flute. I do not have 1 flute, but I do have 2 flute. I also do not have flood coolant, so will have to use mist.

I finally had some success with these parameters:
2000 rpm, 200mm/min, 0.25mm doc, 2 flute, with mist coolant

I guess I should really do some test cuts on scrap, before I start the actual job, given that I know so little about feeds and speeds, and types of metal.

Anyway, thanks for helping

[SCzEngrgGroup]

For such a small cutter, you should be running higher RPM, if you can. You're running only about 60 SFPM, which would be OK for stainless steel, but not brass. Any time you're breaking tools, you're either cutting too deep, or feeding too fast, or both. You should always start with a shallow cut, and see what feedrate works, then increase DOC until surface finish suffers. The deeper you go, the more you'll likely have to back off on feedrate. For soft materials (sounds like what you have), use fewer flutes.

Regards,
Ray L.

[Memran]

My little sieg X1's max rpm is 2000, unfortunately.
But in hindsight I agree, I was being too aggressive for such a small cutter.

A high speed dremel attachment is on my 'to do' list, but it is such a long list!

[SCzEngrgGroup]

Rotary Tool Kit - 80 Piece Set

Might not last long, but at that price, who cares?

[Memran]

Nice, thanks
But I already have the tool, I just need to make a nice mount for the machine

[UUU]

When drilling (by hand) in brass, it's often advised to file off the edges on the drill, so it doesn't "grab" as much. Likewise the top-rake of a lathe tool for brass is level.

Is there any advantage in carrying this over into the milling arena?

[Memran]

Here's the first parts made from sheet brass:



I think with a little tweaking, I think I can get a better finish.

Again, thanks for your help