Sudden endmill breakage and solution

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aarvidsson
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Sudden endmill breakage and solution

Post by aarvidsson » Tue Jul 28, 2015 9:19 am

Earlier today my machine started going through endmills as if there was no tomorrow. I had changed nothing overnight, but in short order I broke three endmills that had been working splendidly previously. As throwing a tantrum has shown not to yield the results I prefer, I decided to think logically instead. After a dead end with re-tramming my wasteboard (which was due anyway) I took a look at runout. And did I have runout. Of the half millimeter variety. Long story short: a miniscule grain of crud had worked it's way into the collet and when tighting said collet the runout became progressively worse. It didn't show when tighteinging by hand, only with the wrench. That one had me stumped for a while, but the solution was simply to clean out the collet and now all is right in my CNC world again. Just thought I'd share i case anyone trips over the same situation.
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WillAdams
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Re: Sudden endmill breakage and solution

Post by WillAdams » Tue Jul 28, 2015 10:54 am

Thanks. That’s a good point. Added an explicit note (though arguably it was covered by manufacturers instructions) to the http://www.shapeoko.com/wiki/index.php/ ... _Checklist
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Gadgetman!
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Re: Sudden endmill breakage and solution

Post by Gadgetman! » Tue Jul 28, 2015 11:36 am

So... Toss collets in the ultrasonic for a few minutes, then give it a nice coat of protective oil?
What kind of oil is the best for protecting parts like these, anyways?
(I've been using air tool oil for other bits of metal in my workshop)
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WillAdams
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Re: Sudden endmill breakage and solution

Post by WillAdams » Tue Jul 28, 2015 12:49 pm

The Precise Bits folks have an actual cleaning fluid which they stock and include w/ their precision collets.
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clockit
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Re: Sudden endmill breakage and solution

Post by clockit » Tue Jul 28, 2015 5:48 pm

i had a similar issue with saw dust accumulating in my collet that would allow it to loosen. and i'm talking about a very small amount. standard operating procedure for me now it to remove, tap, and blow any saw dust out of the collet each tool change...
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Brian Stone
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Re: Sudden endmill breakage and solution

Post by Brian Stone » Tue Jul 28, 2015 6:41 pm

I've honestly never thought about this possibility. I do a lot of mid-job tool changes, often using the same collet, so it's a good thing to keep in mind.
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Hans
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Re: Sudden endmill breakage and solution

Post by Hans » Tue Jul 28, 2015 6:50 pm

Any light oil will do (I think air tool oil would be pretty good). WD-40 will leave an undesirable waxy buildup if squirted in somewhere repeatedly and not wiped away, but if you're putting it on a clean rag or a q-tip and just wiping out the taper, I don't see how it could be bad.
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