What downcut bits have a good tool life?


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Thread: What downcut bits have a good tool life?

  1. #1
    Member TTalma's Avatar
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    Default What downcut bits have a good tool life?

    I like using downcut bits, I normally cut hardwoods, and onion skin the parts. A downcut leaves a nice sharp edge on my parts.

    But I am finding that they don't seem to last long. In hardwoods I normally use a 1/4" bit, .25" DOC, 18000rpm (Spindle max speed) and 150 ipm. Cut part .01 oversize and follow with a full depth pass to clean up. Dust collection running.

    With a new bit I get a real nice finished surface I'm not sure how much I cut but it seems like my downcuts don't last as long as my straight cuts.

    So what bits have you used that have a good tool life?

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    Last edited by TTalma; 10-22-2019 at 12:11 PM. Reason: fixed 1800 to 18000


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    Community Moderator ger21's Avatar
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    Default Re: What downcut bits have a good tool life?

    Try 13,000 rpm, and they should last at least 50% longer.
    Try a coated bit like an Amana Spekta, for even longer life.

    Gerry

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    Default Re: What downcut bits have a good tool life?

    Quote Originally Posted by ger21 View Post
    Try 13,000 rpm, and they should last at least 50% longer.
    ???????
    OP Stated 1800 is max speed of his spindle!!!!!!!!



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    Member TTalma's Avatar
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    Default Re: What downcut bits have a good tool life?

    Quote Originally Posted by breezy1849 View Post
    ???????
    OP Stated 1800 is max speed of his spindle!!!!!!!!
    Sorry mis-typed My spindle does 12000 to 18000.



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    Default Re: What downcut bits have a good tool life?

    Raise your feed rate or lower RPMs. Assuming a 2-flute cutter, your chip load is way too low and your bit is losing its hardness due to heat. The issue is also compounded due to the downshear trapping chips in the bottom of the cut.

    This calculator shows you should be running at 8,000 RPM max at 150 IPM. https://www.guhdo.com/chipload-calculator I see that this is below the range of RPM on your spindle, what is your max feed rate?

    Make chips not dust! A bigger chip will carry heat away from the cut.



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    Member TTalma's Avatar
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    Default Re: What downcut bits have a good tool life?

    I got a new bit I purchased a freud from woodcraft. I tried all of the the suggestions, and what seemed to work well was the following settings:

    15000 rpm, 250 ipm, 3/8" doc, with a full depth .01" clean up pass in 3/4" hard maple. Dust collector was running and the channels were about 1/2 to 1/3 packed at the bottom when done. I cut around 30 parts, the cycle was about 40 min. When it was done I touched the bit, it was very warm, but not so hot that I couldn't keep my fingers on it. I figured this was pretty good and should give decent tool life. All of the chips were tiny squares, not powder like I was getting.

    And on the plus side since I'm doing 3/8" doc instead of the 1/4" that I was doing, my cycle time improved quite a bit. I started an excel spread sheet and will keep track of the number of parts with the settings, and in a few months I will see how I'm doing. I want to try a couple of other bits as well.



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    Member Biggs427's Avatar
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    Default Re: What downcut bits have a good tool life?

    I ran Yonico and Onsrud 57-xxx serie with good success but Onsrud finish is a tad better and last 25%-50% longer. Yonico is almost half the price of Onsrud depending of vendor.

    Mostly in maple, birch, walnut and some birch plywood

    Edit: At work we have FS Tools cutters that are incredible but they cost an arm and a leg.

    Last edited by Biggs427; 10-28-2019 at 12:31 PM.


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What downcut bits have a good tool life?

What downcut bits have a good tool life?

What downcut bits have a good tool life?