Surfacing With Extra Long Tools

[Prototype_guy]

Hi I have some tools to machine that are very very deep. Longest I have to do is going to be 8" of stickout with a 7/8 inserted ballnose. Material I'm machining is A2. That 8 deep length has straight verticle walls to machine all the way down. I'm doing this work on a 3 axis 40 taper mill...

 

 

Any suggestions on amount of material to leave for finishing, speeds\feeds or depths of cut would be greatly appreciated. I know there is no good way to do this, but I have no choice...

[cncchipmaker]

You could possibly plunge mill the whole thing with a long standard end mill and then go back with the ball end mill. Typically I have always left .005 on my surfaces for finish but I have never done anything that you are describing. A pic would help out a lot so we can steer you in the right direction.

[Prototype_guy]

BIGTOOL.mcx-8

 

Here is one example.

[AMCNitro]

The bigger the tool, the better.  Make sure to grind a relief  behind the flutes so it doesn't rub on the vertical walls.  I'd leave at least .01, sometimes leaving more material gives the long tool a bit more support(hard to explain, I know what I mean), too little material and it will want to bounce off the wall, specially with harder materials.  Speeds and feeds?  I dont know, but I wouldn't spin too fast, it will create more chatter.

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[taperlength]

BIGTOOL.mcx-8

 

Here is one example.

I was just doing tool paths on your part and most of it can be roughed out with a flat endmill with 5.50 stickout.

[Prototype_guy]

I've been working my way through some of this stuff... Fun times. Worst so far was a bunch of surfacing with a 3/4 ball that had 6.5" stickout. Turned out ok.  Just got a couple custom long 10" ballnose bodies, with slightly smaller shanks from sterling edge so I can get all the way down some of these walls.