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IndustryArena Forum > MetalWorking > MetalWork Discussion > Cheap vs expensive collets and nuts for aluminum surface finish?
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  1. #21
    Join Date
    Jun 2015
    Posts
    4131

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    anything you can adjust with a tiny set-screw can also be moved by regular cutting forces
    hy goemon that's true, more precise, there is a chance to happen; is not possible to push such systems, as they are fragile

    at least you tried ... if i may ask, what are you going to do now ? what tir did you noticed before starting this thread/conversation, and what tir do you wish to achieve ?

    i would like to sugest 2 rigid solutions :
    ... weldon type with excentric bush : basically, you change arbor, and use a set of bushes; for example, if you noticed tir of 0.01, then you need a bush with excentricity of 0.01; this requires having a set of bushes that is corelated with expected tir ( i have done this )
    ... keep your er chuck, but make it a separate part from the arbor (like a flange), tir being adjusted with screws; the difference between this solution and an adjustable tir collet, is that here you may use bigger screws, that will ofset the er chuck entirely; this again may be shifted by cutting forces, but being more rigid, it will resist better than the adjustable er nut ( i have seen this being recomanded by others )
    * unfortunately, both solutions do not exist as being able to buy them, thus requires to custom build them / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  2. #22
    Join Date
    Mar 2017
    Posts
    926

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    Quote Originally Posted by deadlykitten View Post
    hy goemon that's true, more precise, there is a chance to happen; is not possible to push such systems, as they are fragile

    at least you tried ... if i may ask, what are you going to do now ? what tir did you noticed before starting this thread/conversation, and what tir do you wish to achieve ?

    i would like to sugest 2 rigid solutions :
    ... weldon type with excentric bush : basically, you change arbor, and use a set of bushes; for example, if you noticed tir of 0.01, then you need a bush with excentricity of 0.01; this requires having a set of bushes that is corelated with expected tir ( i have done this )
    ... keep your er chuck, but make it a separate part from the arbor (like a flange), tir being adjusted with screws; the difference between this solution and an adjustable tir collet, is that here you may use bigger screws, that will ofset the er chuck entirely; this again may be shifted by cutting forces, but being more rigid, it will resist better than the adjustable er nut ( i have seen this being recomanded by others )
    * unfortunately, both solutions do not exist as being able to buy them, thus requires to custom build them / kindly

    I don't have the tools to accurately measure runout at high rpm. I've been more focused on surface finish and how hard I can push my machine.

    I found a huge difference between the depth of cut I'm able to take with a quality nut properly tightened vs what I can do with some of my purchasing mistakes. The surface finish is night and day too.

    I could only take super shallow cuts with the worst nuts I own. And the noise at 20,000 rpm is noticeable even with the fan on.

    What I'd look for now is simple solid nuts with well cut threads and no moving parts (so no bearing nuts).

    I made my own extra long top wrench with an extended grip to add leverage. I can now use almost all the threads on the best nut I own. That alone adds an 1/8" depth to what I'm able to cut.

    I could hardly managed two or three turns with the worst nuts. It's like the threads don't line up well.

    My high speed spindle is manual tool change so I don't need to worry about toolholders.

    I found little difference with the collets as long as they are sized to hold the tool properly and can clip into the nut. But, a quality nut made a difference to how the collets performed.

    My Techniks collet that I thought was broken actually clipped in and held a tool on my best nut. I couldn't clip it in or tighten it enough to hold a tool on other nuts.

  3. #23
    Join Date
    Sep 2006
    Posts
    6463

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    Hi.....on the problem of finish I would say that anyone who uses replaceable rotating tools in collets for cutting.....eg an end mill..... will be hard pushed to get the rotating surface running dead true even with the best collet system.

    If the rotating side surface is doing the finishing you'll get cyclic cutting marks in the work surface due to the eccentric nature of an out of round cutting path.........for sizing this is not a problem as you can have a cutter running eccentric and adjust the cut accordingly, but for finishing I would say for PERFECT running a cutter would have to be mounted in a solid holder and ground to size in situ....that will ensure the cutter is cutting in a circular pattern and not on the highest point of it's periphery that a cheap collet would produce.

    In the quest for perfection most people resort to throwing money at more and more cutter holding solutions but how many actually know what the real problem is

    I'm suggesting that a cutter mounted in a shrink fit holder and then ground in situ will run 100% true if the machine mounting the holder and cutter also run 100% true.

    This is just an observation, but as I'm not in production or manufacture the problem for me does not arise........I use cheap EBAY collets and never expect to get a good finish with the side of a cutter contacting the workpiece.

    However, if a cutter is running eccentric even a few microns and the feed rate is high the surface finish will not be even due to cyclic contact of the high point of the cutter periphery only making contact and in that scenario it will not get better unless the feed rate is slowed right to a crawl and the rpm is high.......high rpm would introduce vibration and so the cycle goes full circle.
    Ian.

  4. #24
    Join Date
    Jun 2015
    Posts
    4131

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    I don't have the tools to accurately measure runout at high rpm.
    neither do i
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  5. #25
    Join Date
    Mar 2017
    Posts
    926

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    I don't have any expectations of perfection (especially not on a sub-2000lb diy machine).

    It's really more about not adding additional problems.

    People running small belt drive spindles may not have noticed this but, when working at 18,000-24,000rpm even small issues with a nut not being tight enough, or it being unbalanced can make a noticeable difference.

    The aim for me is not to eliminate all tool marks. It's to make it so tool marks can be removed with with a couple of minutes of light sanding vs hours with the 40 grit.

    I'm generally getting good results at the moment, as long as I use a properly fitting nut that's sufficiently tight...

  6. #26
    Join Date
    Sep 2006
    Posts
    6463

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    What is more to the truth is that nobody has the means to check if a cutter is making a truly circular contact on all cutting edges at the same time during a cycle......only a grinder's wheel with it's multi grain structure having millions of cutting edges that have been dressed in situ will produce a finish that is mirror like...... for instance a surface grinder or cylindrical grinder........so many other factors are present in the equation too.
    In the quest for a better finish some have resorted to second op vibratory and tumbler finishing.....but not many tumblers or vibro finishers will only take out tool marks in specific areas.
    Fine grit blasting can do it followed by a vibro finishing cycle, but it's a very intensive cost program if the need must be.
    Ian.

  7. #27
    Join Date
    Jun 2015
    Posts
    4131

    Re: Cheap vs expensive collets and nuts for aluminum surface finish?

    hello to true up some live tools, or at least to reduce tir, i use excentric bushings, that you simple rotate until tir reduces

    you invest a bit of time to make those, but it helps for the future; also arround here same trick is used to align some components in their final assambled state

    i don't use 20k rpm spindles, those are smaller, so a more gentle aproach has to be used

    as for okuma, they have a function that can syncronize rpm with feeding, thus rotary with linear axis, in such a way, that tir effect is minimized; thus if there are 4 flutes, then machine will make 4 adjustements within 1 spindle revolution; it has it's limitations, thus it won't work the same for a big tool as for a small tool / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

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