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IndustryArena Forum > MetalWorking > General Metalwork Discussion > End Mills - Expectation vs reality
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  1. #1
    Join Date
    Jul 2008

    End Mills - Expectation vs reality

    Hi all,

    Just wanted to see if anyone could offer some insight on a niggling problem i am having. Basically, I see youtube videos constantly showing endmills doing AMAZING things. 4 or 5x diameter length end mills slotting using the full cutting edge of the tool seemingly effortlessly. Will post a link below to a video from the exact tools i run at our shop. Seeing this gets me excited because it shows me the potential of what a tool we actually own can do and the potential to cut production times significantly.

    So eventually, a job pops up which i can use these end mills on (s stright slot in a block of steel) I calculate my speeds and feeds according do the data given by the toolmaker. I stay safe and keep all my feeds and speeds on the lower end of the spectrum (to give me room to build up if everything works well) and I also stay safe and start my cut depth at 1x diamter of the tool. 12mm deep, 12mm diameter tool. I bring my tool in and the second the tool touches the steel i get insane vibration. So, I keep lowering and lowering my cut depth until in the end i could only take a 2mm cut without vibration.

    My Machine/Setups are: Hartford CNC Mill, BT40 Collet Tool Holder, 12mm END Mill, Solid Piece of free cutting steel held in middle of vice with no overhang.

    My question is - Obviously my toolholders are not the most rigid possible and i understand these videos i watch on the internet are setup best case scenarios but should i expect to be able to replicate what i see in these videos? To see a video of my exact tool cutting a full length slot and only be able to use that tool at a fraction of the depth is disheartening to say the least.

    OR - Do you guys think with the above mentioned setup i SHOULD be able to use the tool as i see in videos and maybe there's other underlying issues?

    Just really trying to pick your brains a bit on this. This is not about trying to be the hero ripping off all this material this is about trying to improve efficiency.


    Cheers in advance.

  2. #2

    Re: End Mills - Expectation vs reality

    I would start looking at backlash, spindle bearings, and overall machine rigidity. The tools will run as the manufacturer shows, but it requires an absolutely rigid machine. It also looks like they were getting a lot of chatter on heavy cuts, then are going back and cleaning it up on the finish passes.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
    Join Date
    Jul 2016

    Re: End Mills - Expectation vs reality

    The Machine in the video is like hercules, 12000 RPM with a lot of torque on both spindle motor and the machine itself, if your machine did not get what it looks like in the video then I guess it`s not that strong and powerful, if it vibrates beyond 2mm then you know it`s lacking torque either on the spindle nor the drive motors.

  4. #4
    Join Date
    Jul 2008

    Re: End Mills - Expectation vs reality

    Thank for the replies guys.

    The machine is only about 3 years old and hasn't had a huge amount of use and most of the use it does have it is plastic cutting. I wouldnt expect any bearing wear, backlash etc. Our machine has 15HP Spindle Drive Motor, 301.8Nm of torque and the "load" graph when cutting these cuts is well into the green.

  5. #5

    Re: End Mills - Expectation vs reality

    You need to INCREASE your cutting depth. They are using the full flute length for a reason. Part of that is that is always maintains contact with the part, likely in several locations on several flutes simultaneously. By using a reduced cut height, you are making an interrupted cut - and causing vibration. If your machine is very rigid, you can get away with it, but the more flimsy the machine, the more your need to optimize cutting parameters and workholding to compensate.

    Try going to full depth and play with feeds and speeds to get your slot.

    OR use a smaller dia EM and adaptive rough the slot and contour finish the side walls.

    if you watch the video closely, you can tell they are getting a ton of chatter when they are at reduced DOC as well...

  6. #6
    Join Date
    Mar 2017

    Re: End Mills - Expectation vs reality

    I'm no expert but my personal experience has been that cutting too slow is just as likely to cause issues as cutting too fast or deep. Whenever I try to baby my machine, I seem to end up with a broken end mill.

    I have been using g wizard to set feeds and spindle speed. For me it has produced superior results to other calcs or using the manufacturers specs. It adjusts the speeds based on what you tell it about the stiffness of your machine which makes more sense to me.

    Excess vibration can sometimes be fixed by adjusting the spindle frequency / rpm up or down. I can hear a huge difference to how it sounds when I find the "sweet spot".

    Given how much torque you have, I seriously doubt this is the issue when using a 12mm end mill. I can cut steel with my 7.5hp 24000 rpm spindle and that has a tiny fraction of your torque. You would expect the spindle to stall / get stuck if there was too little torque.

    Also, check your work holding.

  7. #7
    Join Date
    Jul 2018

    Re: End Mills - Expectation vs reality

    Hi Matt - That video is wicked. The chip stream is relentless. To do this you need a very stiff machine. So you need to check all your ways and everything is snug snug and tight. Then it comes down to the static and dynamic stiffness of your machine. Is there any clues to what machine is being used in the video? Peter

  8. #8
    Join Date
    Mar 2017

    Re: End Mills - Expectation vs reality

    It could be smoke and mirrors. They seem to be blasting the heavy-metal music and it seems to get louder for the more demanding cuts. Maybe they are suffering the same vibration and noise...

  9. #9
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003

    Re: End Mills - Expectation vs reality

    I'd get some tooling reps in your shop. Every machine is going to be a bit different, and a tooling rep should know best what their tools can do on your machine.

    UCCNC 2017 Screenset

    Mach3 2010 Screenset

    JointCAM - CNC Dovetails & Box Joints

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

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