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A curious case of exploding end mills

To be clear. It has been 2 or 3 times out of 1000's of tools so not common but noticeable. I would get your local rep involved they would be more helpful into digging into a problem on the manufacturing floor. Pull lot#'s of the carbide etc. You could probably guilt them into some free tools as well. I think that's the least they could do after trashed holders.
 
Take the tool out of the spindle and clean the inside of the spindle taper. Check how many chips are getting into your carousel and on the tapers on the other tools.

Check the taper on the holder you are using for mashed chips. Check all of your tools in your carousel and clean all tools and carousel of any chips. You are flinging chips at very high speeds. I thought you had a three flute end mill not 4?

It may only be a matter of seeing where there are ops where a lot of chips fly mixed in with coolant. You should step process each op and blow everything off before the tool change and note chip disposition.

Only one thing I would consider first. I always note that kind of thing right off. Simple yet very important usually that can be the case when problems seem to pop up out of nowhere.

Yep, I checked that after the first tool break. I popped the shrink-fit holder out, checked the toolholder taper and the spindle taper (both pristine), got a clean Kaiser NBC chuck out of the drawer, wiped it clean, assembled with a fresh tool, put it back in the spindle, touched it off, re-posted only the slotting op with reduced speed/feeds, blew off the part to check for damage, ran the new code, and the new tool failed a few minutes later.

In general my toolholders stay pretty clean. The Speedio "turret" does a good job of keeping them chip-free.
 
Considering they broke in the collet or toolholder makes me think carbide. What flute length? You REALLY need to use .156" stubs for that, you can run them a lot harder than 1/8" mills IME. Harvey would be my current pick for that exact size and flute length.

Yeah? If I end up doing a bunch more of these I was planning to grab a 0.1875" 3-flute rougher and just take a slot down the middle, then come back and take the last 0.004" per side as a finish pass. (Unfortunately I didn't have any on hand yesterday... thus the 1/8" approach.)

Forgot to mention, these were 3/8" LOC IIRC.
 
Yep, I checked that after the first tool break. I popped the shrink-fit holder out, checked the toolholder taper and the spindle taper (both pristine), got a clean Kaiser NBC chuck out of the drawer, wiped it clean, assembled with a fresh tool

Ouchies. So not a generic ER collet, but a NBC? That's like three or more times the cost. The suck quotient is high with this one...
 
HUH?! You must ramp a whole lot different than I do. My math says a 2' ramp from zero to -.127 will take 3.639"

Anyways, my money is on bad carbide. And, I freaking HATE when they take the collet with them! :angry:
Exactly. First pass he'll be at full depth, since his part is 3.3" Thanks for proving my point.:D

I'm impressed i was that close just approximating it in my head.:cloud9:

Yeah, likely bad carbide since other cutters worked.
 
ramping at 2° you'd get to full depth in short order, which at .127" is the full dia (1xD). Combine that with .0004 chip load, quoted, it sounds like you have a mess of vibration and rubbing the tool to death.
keep the cut depth under .03 and take an actual chip, is how i'd go.
6061 is sticky and alloyed with silicon, but it doesn't sound like you have a coolant lubricity or flow issue.

was literally gonna say the same thing. reduce your ramp parameters and increase chipload.
 
was literally gonna say the same thing. reduce your ramp parameters and increase chipload.

It may not be optimal, but I've had reasons to take cuts like those and not had endmill break on me without some reason why - usually BUE, but sometimes excessive vibration due to stickout or some other issue.

The way these failures have been described doesn't seem to follow that pattern.
 
Me thinks there is a miss-understanding, or miss-communication here someplace? You said:

ramping at 2° you'd get to full depth in short order, which at .127" is the full dia (1xD).

I said:

HUH?! You must ramp a whole lot different than I do. My math says a 2' ramp from zero to -.127 will take 3.639"

Anyways, my money is on bad carbide. And, I freaking HATE when they take the collet with them! :angry:

To which you replied:

Exactly. First pass he'll be at full depth, since his part is 3.3" Thanks for proving my point.:D

I'm impressed i was that close just approximating it in my head.:cloud9:

Yeah, likely bad carbide since other cutters worked.

The way I interpret your first statement: He would be at full depth in .125". "full diameter" of the end-mill.
It sounds like a straight slot to me. Slots are measured in width x depth as far as I know?
So, what did you mean by "at full depth by 1xD"? Diameter of what?

EDIT: I guess now that I ponder it, I can only assume you are saying he will be at full depth and cutting the full depth of the slot before he changes directions? In other words: he will be at full depth before he travels full end-mill diameter in Z. Not how I would word it. But, yea, I guess........
 
Ouchies. So not a generic ER collet, but a NBC? That's like three or more times the cost. The suck quotient is high with this one...

Yes, this was a very bad day. I scrapped two on-size NBC collets and two shrink-fit collets. $400 to cut a few lousy 1xD slots in 6061. Not counting the end mills.

I admit I posted this up because I was furious. :)
 
Yes, this was a very bad day. I scrapped two on-size NBC collets and two shrink-fit collets. $400 to cut a few lousy 1xD slots in 6061. Not counting the end mills.

I admit I posted this up because I was furious. :)

At that point, bust out the chisel, so you only lose $300 on the job :D
 
Can't say much that hasn't already been said about your recent issue. Thought that goes through my head when I get past sucj issues is to keep an eye peeled for other issues that come up on this machine in the near future that might point to a machine related common source...
Not familiar with Speedio....how is the draw bar? I had endmill breaking issues (larger diameter however) on a machine that I discovered had broken Bellvuille???? washers and wasnt holding the tool holder good enough
 
Can't say much that hasn't already been said about your recent issue. Thought that goes through my head when I get past sucj issues is to keep an eye peeled for other issues that come up on this machine in the near future that might point to a machine related common source...
Not familiar with Speedio....how is the draw bar? I had endmill breaking issues (larger diameter however) on a machine that I discovered had broken Bellvuille???? washers and wasnt holding the tool holder good enough

I would blame the programmer
 
Can't say much that hasn't already been said about your recent issue. Thought that goes through my head when I get past sucj issues is to keep an eye peeled for other issues that come up on this machine in the near future that might point to a machine related common source...
Not familiar with Speedio....how is the draw bar? I had endmill breaking issues (larger diameter however) on a machine that I discovered had broken Bellvuille???? washers and wasnt holding the tool holder good enough
No bellevilles, they use die springs instead.
 
This is the broken (shank) end. Almost all of the broken shafts have that shiny bright line across them.

View attachment 320982

It's a great image of your gloved hand, when do we get to see the endmill? :D

Yeah, I'd bet dollars that's a flaw in the endmill blanks, I've never seen a shiny line like that in my broken carbide.

If you found any more broken pieces, I'd like to see them. If you can get more pics up please do, or if you'd like, I can give you my address to ship them to me. I'd be happy to send them back after going over them, just want to view in person a failure I've not seen before.
 
I am kinda fuzzy here on your DOC, from what I read your DOC was ~2" which to my thinking is a lot of stick out for an EM of that Dia. Have you tried just air plast for chip evacuation. I hardly work with Al at all, so please take my suggestions with that in mind. Also you folks that are more knowledgeable Al please tell me if i got anything correct here.:rolleyes5:
 
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I think you are misreading - DOC is 0.127" (for a 0.125" endmill, so 1xD) but maybe I'm misreading? I've always had great success welding endmill flutes to overflowing by trying to mill aluminum without flood coolant....

(OK, seriously, I worked aluminum that way for years and you do find ways, but aluminum generally likes coolant, lots of it.)
 








 
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