Tool End Mill Failure
- Thread starter YYCHM
- Start date
Tool
The up chip looks like it dug in, but that could easily have happened when it broke. Looks like a thin cut & only on the bottom cutting, no side cutting (only an issue on excessive removal). Your chips are silver not blue or tan so not working hard or bad grind. The chip direction looks like FWD not REV by accident. Any chance the EM became loose in it's holder? Or quill/table floating somehow? Or part was able to shift rotate slightly within vise jaws? Its a big honkin EM, one would think takes a lot of torque to snap.
I agree with @PeterT . I see nothing awry there. Looks like conventional milling, your cuts don't seem to be very deep. Don't know the feed rate. But nothing catches my eye. I see no red flags.
I'm not really a fan of big flute end mills like that. Guessing it didn't cost you as much as a really good one would. My bet is that is the beginning and end of the story. No way it should have broken like that. But..... you should be very thankful the endmill broke instead of the mill itself.
I just think it was a bad endmill.
I'm not really a fan of big flute end mills like that. Guessing it didn't cost you as much as a really good one would. My bet is that is the beginning and end of the story. No way it should have broken like that. But..... you should be very thankful the endmill broke instead of the mill itself.
I just think it was a bad endmill.
Former Member
Guest
Yes twice on a 1" HS endmill, very light cut. As near as I can guess is the bit deflected under cutting loads (not uncommon) however because it was HS tooling it rebounded slightly, caught dug in and BANG snapped. This rebound together with endplay in the slides or vertical feed is just compounded.
Carbide does not flex or catch as easily IMHO. One of the reasons I use carbide.
Matt-Aburg
Ultra Member
I have many old HSS, some this same style. They are in a box all rusted,,, I stick to carbide now..
Did the part move? I’ve broken EMs when I didn’t have good solid work holding. What rpm and what depth ? Is that known steel or mystery meat - did you hit a hard inclusion? You’re traversing left to right and using conventional not climb milling? What step over?
WOW - 6 questions in a 2 line post.....
Did the part move? - Most likely.
What rpm and what depth? - 500 rpm, 0.001"
Is that known steel or mystery meat? - Mystery (a Kevin D donation).
Did you hit a hard inclusion? - Dunno
You’re traversing left to right - Yes
What step over? - 0.375"
Mostly I'm curious if people have had one twist off like this. I've toasted other endmills by breaking flutes etc. but have never had one fail in torsion like this. 1/2" shank sheared right off.
Former Member
Guest
Conventional milling pulls the work and endmill together so backlash and flex are pull towards each other. Climb mill pushes them apart and should a part grab they are very rapidly pulled together increasing the cut (grab), additionally in climb milling the cutter is pulled out if the holder more so than Conventional milling which again leads to a great chance of breakage.
Until I've done the ballscrew replacement to nearly eliminate backlash primary cutting is done with conventional, even with carbide
Until I've done the ballscrew replacement to nearly eliminate backlash primary cutting is done with conventional, even with carbide
Some one needs to explain to me how conventional milling applies when milling a slot???
In this case I was milling a flat with only two surfaces interfacing with the tool. The back vertical face and the bottom flat and as far a I can tell I was conventional milling as in driving the work piece towards the advancing cutting edge.
In this case I was milling a flat with only two surfaces interfacing with the tool. The back vertical face and the bottom flat and as far a I can tell I was conventional milling as in driving the work piece towards the advancing cutting edge.
Good question. I've seen articles written on it. But my summary of them is that the forces balance in favour of the conventional milling. It is unlikely that the climb side can force the conventional side to move and that prevents the typical climb grabbing failure.
But I'd love to see a comprehensive analysis too.
My assessment of looking at your failure photo ruled out a typical climb milling failure. You further confirmed that it was conventional. So I'm still in the camp of a bad endmill or a material inclusion in your material.
Never except with tiny endmill (1/8 etc).
^^^^ this ++
Where did you get it?
Former Member
Guest
Flawed no, it is flex and grab under load, happens a lot more often than you expect with HS cutters.
If you look at the photo you see the grab moment that initiated the failure.
I do have one question, power feed or hand feed? I'll bet hand feed as it varies in loading and flex even if you are good.
With Carbide and CNC I have done significantly higher feeds and speeds that would destroy HS cutters.
If you look at the photo you see the grab moment that initiated the failure.
I do have one question, power feed or hand feed? I'll bet hand feed as it varies in loading and flex even if you are good.
With Carbide and CNC I have done significantly higher feeds and speeds that would destroy HS cutters.