Milling deeper than flute length, a no-no?
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  1. #1
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    Default Milling deeper than flute length, a no-no?

    I had to make a cover out of a chunk of 1-1/2" thick piece of 6061, requiring me to mill a big pocket 1.2" deep. I used a 1/2" carbide endmill with a 1" flute length to do this, taking .200" deep passes since that's about all my BP clone type cnc will handle, particularly in the beginning of each cut pass where it has to do full width slotting for a while.

    I've seen references in the forum to not milling deeper slots or pockets than the flute length on the endmill, at least not without a reduced neck on the endmill.

    However I've always broken this rule as I did above (although only by .2").

    Obviously you can't take a deeper step cut than your flute length, but as long as you abide by that what is supposed to go wrong when your total cut depth is more than your flute length, I've never had a problem with it and I'm not sure what the dangers are.

    Paul T.

  2. #2
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    You can but like you said you need to reduce your shank diameter a bit. Also you need to make sure you have enough room for chip evacuation.

  3. #3
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    I think the "rule" is null and void once the shank is smaller than the flute diameter, especially in soft stuff.

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    I've done it when I had a emergency job and no appropriate endmill, the main thing it screws up is your surface finish, since the chips get rubbed in between the endmill and the wall. The biggest danger would be a broken endmill especially the smaller endmills

  5. #5
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    Also keep in mind most carbide endmills cut undersize, usually a thou. or 2 on the flutes which will cause the shank portion to rub on the previously machined wall possibly causing deflection of the part.

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    I do it all the time. Reduce the dia down to where thje flutes actually start to cut (where the land starts) by a couple thou. You can run it without but you will have some rubbing.

  7. #7
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    1.25" deep fins cut w/ std Hanita 1/4".
    Attached Thumbnails Attached Thumbnails case-1-001-small-.jpg  

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    If you were cutting a slot the full width of the cutter deeper than the flutes you would have no way for the chips to get out. Obvious no no. From the sounds what you did was no issue at all as you were doing a pocket and never buried the tool so that there was no way for the chips to get out.

    Bob Looney that is a very impressive piece of work you posted there.

    Stephen

  9. #9
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    Bob, cool part!!!

    If you have to do this allot check out Harvey tool or some of the others that make stubby long reach end mills with relieved shanks.

  10. #10
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    thanks for the props.
    Harvey and Hanita tools are awesome.

  11. #11
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    Seems latley ive had to backgring alot of tooling. theres a part i have to make where the corner rads are .065. the slot is 1.25 deep so ill take a standard 4VF series varimill and setup a spin fixture on the grinder and neck it down about .010 just enough so it doesnt rub. set the feed real slow and go hangout in the office for awhile. "Glad the job is T&M". only bad part is my hearing isnt good enough where i can hear the mill break over the 10K spindle.


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