End Mills, The Nitty-Gritty: Cutter Engagement and 'Chatter'

Hello everyone, welcome to At-Man Unlimited. End Mills, where the metal hits the work piece. They make the chips actually fly. The final link to making good parts.
When you starting getting Chatter it can be frustrating and time consuming to solve the issue. Here we will dive a little deeper into how the depth and width of cut can affect the forces that induce chatter.
Please keep in mind throughout this series that this is for entertainment only. While I try my best to have the facts straight I am not a tool designer or supplier. Some items in here are my opinion and should be taken as such. What works for me may not be right for you.

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[EZ_shop]

Best explanation I've ever heard on chatter. Good job Micheal, I get it now.

[rdavit]

Outstanding explanation! 27 years ago, my mentor, an old school German die watch me on a Bridgeport for a few minutes, pick up a few chips, state "your feed is 10% to fast and your speed is to slow"...."chatter is about instability, poor chip a healthy cut". It was about "feel" vs. feed and speed does your part look like (63 RMS or better) and what color is your chip. applies.
Awesome post!

[owievisie]

Damn I freaking love how you drew it out. Gives me a nee perpective to look at these problems

[luiasori]

Very interesting thank you for sharing. May I add on top of that nice explanation, that shallow radial depths of cut also can potentially cause chatter, due to the normal cutting forces will tend to push the tool away more intensively. Especially on difficult to cut materials such as Nickel alloys

[NicosM]

I have 3 differents books on machining.
None of them mentions this.
I'm so glad this video exists !
Thank you.

[ShdowHunter]

These two videos actually helped me identify some of the chatter I've been having, as a brand new and learning machinist, thank you very much.

[Sketch]

That's an awesome demonstration...Looks like we need to math out that perfect depth of cut to width of cut ratio depending on the number of flute, helix angles and the cutter diameter!

[PeteBrubaker]

The intro had me laughing pretty good. You know, most of this stuff I thought I knew pretty well, and I did somewhat. But damn man, you have a great style of explaining things. You also cover a lot very well in a short amount of time. I've really been enjoying watching your channel.

I'll start posting some videos when I start assembling the project I bought. Thanks for sharing!

[sunppaa]

Hi Tim and Huge thanks for the vid!

I've been having issues with chatter using adaptive roughing (milling deep slots) strategies of Fusion 360. I guess I started at a very conservative stepover and it was so shallow that only one flute was cutting at some points. The most problematic point is when exiting the curved cut. Fusion says it keeps tool load constant. But when exiting and entering cuts, they of course have to start from zero. I guess when the cut starts, the stepover is thinner for a shorter period of time compared to exiting the cut. So even if the stepover is large enough in the middle of the cut to utilize more than one flute at once, at starts and ends it isn't, which causes chatter.
Until now I have dealt with the problem by just lowering stepover even more, which just eases the force of the impacts, but does not help at all to even the load, which would be the best thing to do. So I think I should try to increase the stepover quite radically.

In other words, go real light or go hard.

What do you think about this?

Sometimes is really helps to stop banging your head against the wall for a while and instead think about what you doing wrong. Way too easy to forget that most of the time :-). Sometimes you still just end up banging your head against the wall a little lighter :-D! Thanks again so much!!

P.S. I also have some doubts about my spindle taper. I'm sure it has never been reground. It looks and feels smooth but how good the fit actually is I have no idea. Should remove the flange on a tool holder so I can turn it in the spindle with some blue. Also no idea on the condition of the drawbar. Are you happy with the rigidity of your Fadal?

[johnburke]

Getting into John Saunders territory with your explanations. Both of you are very good with the presentation and explaining it in a fashion that us dunderheads can understand.

[hunterau]

Great video, very informative, thank you

[samp.]

Thank you great video for a refresher on how to avoid simplistic chatter. 👍

[gbowne]

Radial chip thinning is a phenomenon that occurs with varying radial depths of cut, and relates to chip thickness and feed per tooth. While these two values are often mistaken as the same, they are separate variables that have a direct impact on each other. Feed per tooth translates directly to your tool feed rate, and is commonly referred to as IPT or chip load.phenomenon that has been well understood for decades. It is the simple observation tha when the step over is 50% of the tool's width or greater at a given feed rate, the width of chips remains constant. However, when the step-over is less than 50%, the chip width becomes progressively smaller as the step over
decreases
Why is it important to know this? Because most of the heat generated in the tool and the steel part is removed, not by
coolant, but by the chips. If you decide (for good reasons) to use step overs smaller than 50%, you will need to run at a faster feed rate to get the chip thickness back up to target. If you are not cutting at the targeted chip thickness, your heat management will be off because the chips do not have the mass needed to retain the heat, pull it away from the tool and part, and put it into the chip pile.

[Venthorn]

So if you had a wide indexable cutter, like 1" or so, you'd actually want a higher flute count rather than a lower flute count, even if you couldn't feed it fast enough to satisfy that many flutes (due to a lower-HP machine)?

[sellenger]

As always a great vid. I'd love to see a vid on how to sharpen your own end mills. Also still waiting on your ballbar vid :)

[learningtolive]

Great. Thanks a lot. this info really sets up how to plan a good cut.

[m]

I learnt something new. Thank you and i will apply this knowledge to my work. Peace

[FretsNirvana]

What a wealth of knowledge. Thank you. One question ...why in the world would you then want a non-helix end mill? It seems that from this video it would always produce chatter.

[katawatenshu]

incredible informative to assist in endmill selection

[alexcalibasi]

That means mastercam sucks cuz u can't see flutes?