A curious case of exploding end mills - Page 3
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  1. #41
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    Try a 3 degree ramp, 10k rpm (just for the ramp), and 25ipm. I have had 1/2" endmills blow up from a not steep enough ramp angle.

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    I ran another one of these parts today with an OSG 3-flute 1/8" tool in a regular ER collet chuck. It ran perfectly fine, no squealing on entry, absolutely no visible wear. So I'm really willing to believe it was a bad batch of carbide from Helical. (I don't mean to throw too many rocks there, I still like their HEV-5 a lot for example, just not the aluminum stuff.)

    I found a few more broken shanks in my bucket of shame. Cropped down to not offend with too much finger showing

    Also attached: the part, a running photo to show why I'm not worried about chip evacuation.

    carbide.jpg
    part.jpg
    running.jpg

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    Weird, I don't think I've ever had one break on the shank like that.

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    Quote Originally Posted by trochoidalpath View Post
    I ran another one of these parts today with an OSG 3-flute 1/8" tool in a regular ER collet chuck. It ran perfectly fine, no squealing on entry, absolutely no visible wear. So I'm really willing to believe it was a bad batch of carbide from Helical. (I don't mean to throw too many rocks there, I still like their HEV-5 a lot for example, just not the aluminum stuff.)

    I found a few more broken shanks in my bucket of shame. Cropped down to not offend with too much finger showing

    Also attached: the part, a running photo to show why I'm not worried about chip evacuation.

    carbide.jpg
    part.jpg
    running.jpg
    While I agree with the general consensus (bad carbide). Do you have any support under the center of that part?
    By the time you get all those slots in there, it ain't very rigid anymore. Harmonics are your worst enemy.
    Cant tell from the pic if the part is clamped down? Or clamped in the vise? If you are squeezing that in a vise, your asking for problems.

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    I'm wondering why you're still giving us the finger!

    No, actually I'm wondering why that's not a laser part.

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    We had a bad batch of endmills from Helical. Found out after blowing up 8 of them in proven production runs. We grabbed one from the bottom of the drawer and had no problems running for a month. After more investigation the grinds were very obvious how different they were under a microscope. Took them nearly 3 months to make it right. So with their lack of customer service. We been swapping helical out for other brands like Imco.

    I think with them being purchased their quality is going down hill fast.

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    Quote Originally Posted by wheelieking71 View Post
    While I agree with the general consensus (bad carbide). Do you have any support under the center of that part?
    By the time you get all those slots in there, it ain't very rigid anymore. Harmonics are your worst enemy.
    Cant tell from the pic if the part is clamped down? Or clamped in the vise? If you are squeezing that in a vise, your asking for problems.
    Good catch.

    The part is done in three separate ops. Op 1 (obverse preparation) has the stock in Talon grips, drills the clearance holes at the corner, then counterbores and chamfers. Op 2 (obverse) the part is held from those counterbored holes to a fixture, finishes the top, roughs/finishes the profile, roughs/finishes the slots to .127" depth (leaving about .125" solid underneath), chamfers everything. Op 3 (reverse) the part is flipped over and held down to the fixture plate, cuts a huge rectangular pocket .127" deep over all the slots, chamfers everything. The slots are spaced 5mm apart so there is also way more material there than you might think.

    It's very quiet when it's running.

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    Quote Originally Posted by Milland View Post
    I'm wondering why you're still giving us the finger!

    No, actually I'm wondering why that's not a laser part.
    I'm Italian, I can't say anything without hand or finger gestures....

    It's not a laser/waterjet part because I'm only making two.

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    Quote Originally Posted by Larry Dickman View Post
    Chinese Aluminum? It'll bite you in the ass every time
    I dug up the MTR -- looks like was Russian aluminum, comrade. (Never seen that before, so who knows?)

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    Quote Originally Posted by trochoidalpath View Post
    Good catch.

    The part is done in three separate ops. Op 1 (obverse preparation) has the stock in Talon grips, drills the clearance holes at the corner, then counterbores and chamfers. Op 2 (obverse) the part is held from those counterbored holes to a fixture, finishes the top, roughs/finishes the profile, roughs/finishes the slots to .127" depth (leaving about .125" solid underneath), chamfers everything. Op 3 (reverse) the part is flipped over and held down to the fixture plate, cuts a huge rectangular pocket .127" deep over all the slots, chamfers everything. The slots are spaced 5mm apart so there is also way more material there than you might think.

    It's very quiet when it's running.
    Sounds like a plan!

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    Quote Originally Posted by trochoidalpath View Post
    I dug up the MTR -- looks like was Russian aluminum, comrade. (Never seen that before, so who knows?)
    Comrade, in Soviet aluminum, material bite endmill!

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    Quote Originally Posted by trochoidalpath View Post
    I had an expensive day today and I am trying to figure out why.

    This 6061-T6 part has a number of 0.196" wide slots, either 1.417" or 3.346" long, 0.127" deep. Roughed them out with a ramp down at 2 degrees to full depth, leaving 0.005" per side for a finish pass later on. I was using Helical H40ALV-3 1/8" end mills in either Kaiser NBC with on-size collets, MST shrink-fit collet holders, or ER collet chucks. Running on a Speedio. Very good chip evacuation with flood coolant (Trim 690XT).

    I blew up no less than six end mills. Even for me this is egregious.

    I kept backing off the speed and feed, and ended up at very conservative full slotting numbers (16000 rpm, 19 in/min, 0.060" ramp depth). The broken end mills were pristine -- no broken tips, no visible wear, no chip welding whatsoever. Four of the six broke inside the nose of the collet, which trashed two collets and two shrink-fit collets.

    That ran me out of 1/8" aluminum-specific end mills, and I needed to get the part done, so I grabbed a random 1/8" 4-flute and ran that. It finished the job without complaint.

    Maybe a bad batch of carbide from Helical? Those were all ordered at the same time, and have sat in my drawer until today.

    I'm just pissed at scrapping a bunch of tooling and I'm trying to figure out why.


    Look at the retention knob , make sure it’s tight and make sure tool holder is secure in the spindle.make sure that windmill is rotating the correct way, look to make sure flutes are right handed. Happened to me once . And I had Never heard of left handed flute endmill.

  16. #53
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    i think you would have better luck rough and finish with a stubby 3/16"
    Helicoil is a good brand, weve been using for years. just off the shelf holders and er16 squeeze collets. we have also been testing, Core Cutter brand, which Dan also designed.

    we do all kinds of stupid little features like that all day, every day. Nature of the beast.

    Anyway, i would run that 3/16" at 9850 rpm, ramp in at 35." ipm, then back to the other end at full depth. then finish slot, at 65. ipm.
    just my .02. Good luck


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