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Down Cutting Endmills

Discussion in 'General Talk' started by Colin Mccourt, Apr 21, 2019.

  1. Colin Mccourt

    Colin Mccourt Journeyman
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    I can see now even with me performing a few simple projects that in certain areas a downcutting endmill may be a better choice of tooling bit than an up cutter. I may want to add a few to my ever growing arsenal of bits.
    I am starting to amass quite a few of these bits now, most of the cheap Chinese origin, Nothing worse than wanting to perform a simple CNC task or otherwise and not having the correct or adequate bit or tool to hand.
    All that said, and me still being a relative novice, I would like to add some downcutting endmills to my collection, just in case.
    On Amazon and the Bay of Fleas, I have come across some of these bits with the same branding as my already impressive Chinese mills. Problem is most or all of them come with the strapline that they are Left-Handed bits e.g. 3.175mmX17mm Left Handed 2 Spiral Flute Bits Down Cut Carbide Endmill.
    Can someone point me in the right direction for these bits please that are compatible (3mm are fine)
    also in my search, I find combo cutters (presumably) that state up and downcutting. In what scenario would one want to use this type of bit
    Regards
    C
     
  2. sharmstr

    sharmstr Master
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    Hey Colin. Downcut end mills have a left hand spiral. This pushes the chips down, hence the name. Good for thin stock or where you have your good side up.

    Here's a good video on the difference of up, down and compression bits:

     
  3. Colin Mccourt

    Colin Mccourt Journeyman
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    Many thanks @sharmstr
    much appreciated I'll go ahead and order some
    Regards
    C
     
  4. sharmstr

    sharmstr Master
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    The first cutter I bought for my workbee was a compression bit. I had no idea how to use it properly and was very disappointed. In my case, plunging (which you need to do with these unless you come in from the side) on my massive workbee sucked. So I started ramping the cutter into the stock. A big mistake with the compression bits. Now that I have a stout (modified) workbee, I'll probably try it out again.

    I did a quick search on ebay for compression bits. It seems that most of them dont tell you where the transition on the bit happens. You need to be careful of that I'd think. If you need to plunge down farther than your machine can handle, it will be an issue.
     
  5. GrayUK

    GrayUK Openbuilds Team Elder
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    If I needed to make a 5mm slot, for instance, I'd use a 3mm "up-cut" down the middle, to remove the bulk, and then remove 1mm with a down cut on either side to finish.
     
  6. Colin Mccourt

    Colin Mccourt Journeyman
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    In addition to these, I have come across Tapered Endmills, of the ball-end variety, presumably, they are for finishing 3D work. Forgive me for the newbie style questions as I'm on a learning path with this hobby.
    When would you use these and how do you set them up in the tool library, what parameters etc?
    All help appreciated
    Regards
    C
     
  7. sharmstr

    sharmstr Master
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    Someone with more experience using them will probably answer, but one benefit is strength. If you require a very small ball end mill traditional straight shafts have a smaller cross section as opposed to tapered. Tapered endmills are good for cutting tapered walls (think cooling fins).
     
  8. sharmstr

    sharmstr Master
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  9. Colin Mccourt

    Colin Mccourt Journeyman
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  10. sharmstr

    sharmstr Master
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    That's right. I forgot. I need to keep notes on all of you. LOL
     

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