Another feed rate, cut depth question

[nervis1]

Kinda related to the last one but more specific...ahem...here goes...

I have a contour to cut and said contour bends in on itself such that the largest cutter I can use is a 1/8 end mill. I got a name brand made in the US of A carbide, kick ass 1/8th end mill and it broke. As I'm cutting out these little pieces I think they rattle around just before they let go and cause a lot of chatter...= a broke tool eh?

My question is would it help to go faster, slower, more spindle speed?

My CAM program gave me 6 in/min and 6k spindle speed. This is with a .05" depth of cut. Would I be better off at say .02 and a faster feed?

[Ken_Shea]

Nervis1, how appropriate

What is the material you are cutting and at what RPM?

This will need to be known before anyone can suggest a solution.

Ken

[HuFlungDung]

Nervis1,

Do I understand that it is the cutout that is letting loose and jamming to break your tool? If so, the solution is to rough out all the material so that there is no chunk to contend with. Either that, or you have to figure out a way to secure the cutout so that it cannot move as the last "tab" is cut through.

I don't know how long the 1/8" carbide is, but IMO, they are generally too long to last when doing a full diameter cut. I usually shorten them up so that there is only a 1/4 inch of useful flute length. Then, they seem to be stiff enough to do some cutting for a while.

I cut the tool off with diamond wheel and then regrind some end clearance on the tool's end.

You might also consider trying a HSS cutter. You cannot run it nearly as fast, and it should be flooded for cutting, but HSS is tough stuff compared to carbide.

[wms]

Dave,

Hu is right. I have done a lot of what you are talking about, cutting all the way around and letting the part fall or just sit on the plate underneath. And HSS will be much tougher, carbide is usually to brittle.

I also slow the last little bit down, right before it lets the part go, to about 1/4 of normal feed.

Even at that you will lose a tool now and then due to jamming, and not the kind on the radio. So turn up the blue mood lamps and jammm away.

[Ken_Shea]

This will need to be known before anyone can suggest a solution.

Thanks a lot Ward and Hu, make me wrong again

BTW HU, Neat tip on shortening up the cutter for stength.

Ken

[nervis1]

I knew I'd forget a detail...

It's T6 6061 Aluminum
the depth final is -0.5 so I have these loooong 1/8th cutters, pretty delicate looking. I like the hog idea, I could hog out some of the features but others are just too close together. That would save that little 1/8 guy from cutting the whole thing though. What do you all think about a lighter cut, like .02 at a faster feed, say 8-10 with HSS (flood cool as usual)?

It looks like I need an abrasive waterjet, just have to figure out a way to convince the wife.....nope better not push it.

[nervis1]

I just realized that everthing I know about feeds and speeds came from videoclips of CNC machines on the History Channel and Onecnc.

[HuFlungDung]

Yes, Nervis1, I noticed the various nooks and crannies on that part you are making (the "knuckles" I am thinking of).

You might try plunge roughing with a slightly smaller twist drill in those areas before you get to contouring. Then, switch to an HSS slot drill to plunge cut between the holes, then get to contouring.

Actually, I've never used the plunge roughing cycle yet in OneCNC Mill Expert, but this could be a good application for it.

[BIG AL]

[SIZE=4]THEY AIN'T KNUKS