Pull Stud Broke - Brother Spindle Trashed - Page 4
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  1. #61
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    Quote Originally Posted by Mickey_D View Post
    When I called Maritool before ordering about $1500 worth of ER-20 and ER-32 holders, pulls studs and a face mill holder I asked the person about what studs were needed and was told that the standard non-coolant through studs would be fine on the regular and not high torque spindle. That is whey I ordered them.

    Boy - if there is a good / better / best option, and I was lookin' to put a 2" face mill (with extension) in a 30 taper machine - I'd prolly opt for "best" for that one.

    Is there a way to tell the diff between Good and Best so that they don't git mixed up when robbing from Peter somewhere down the road?


    edit:

    If it had been determined by someone to make a "best", and a 2" face mill (on extended holder) doesn't meet the need for it, at what point would the threshold be for such item?



    ----------------------

    Think Snow Eh!
    Ox

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  3. #62
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    Quote Originally Posted by Ox View Post
    Boy - if there is a good / better / best option, and I was lookin' to put a 2" face mill (with extension) in a 30 taper machine - I'd prolly opt for "best" for that one.

    Is there a way to tell the diff between Good and Best so that they don't git mixed up when robbing from Peter somewhere down the road?




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    Think Snow Eh!
    Ox
    Good question Ox, I find that paint markers dont hold up well in machining environments.

    Charles

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    Quote Originally Posted by Mickey_D View Post
    It did not over power the drawbar spring and pull the tool out ...
    Not sure why you are certain that the drawbar force was not exceeded. Here is a possible scenario:

    1. Part lifts
    2. Facemill digs in
    3. Downforce from the facemill is greater than the drawbar force so the tool + pullstud (still intact) + drawbar are pulled down
    4. Tool can now bang around since it is not locked in
    5. Pullstud breaks due to bending forces as the tool bangs around
    6. Drawbar pulls back up to the nominal position

    So, in this scenario, the pullstud broke as a consequence of the tool not restrained in the spindle taper.

    Going back to the pictures -- picture #5 seems to show an extra drawbar divot -- normally there would be 4 divots spaced 90* apart. I see an extra divot at an in-between location. Unless this pullstud was reused from some other tool, the only way this can happen is if the tool is pulled out of the taper and rotates relative to the spindle keys.

    Regards.

    Mike

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    There is no doubt that sounds like an aggressive setup.

    I find failure analysis fascinating.

    Here is my 3 worthless cents.

    The manufacturer should be given the opportunity to do their own failure analysis, its not like Charlie Fung is asking for it to be sent back so it can be melted down and made into more pull studs... Regardless of the cause it is a reputable manufacturer of high quality tooling. Too much finger pointing with too little evidence to back it up

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    Quote Originally Posted by Ox View Post
    Boy - if there is a good / better / best option, and I was lookin' to put a 2" face mill (with extension) in a 30 taper machine - I'd prolly opt for "best" for that one.

    Is there a way to tell the diff between Good and Best so that they don't git mixed up when robbing from Peter somewhere down the road?




    ----------------------

    Think Snow Eh!
    Ox
    If buying from Mari Tool? Yes.
    Franks studs are good. All black, standard lengths. Good stuff, nothing wrong with them.
    JM-P studs are longer on the thread end, and finish ground on critical diameters/faces after black oxide (and cost a hell of a lot more).

    BT30 Pull Studs - Retention Knobs - MariTool

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    I'm very sorry to hear of your misfortune with a pull stud. I have seen a couple pull studs catastrophically fail over the years from a variety of vendors. A sad and expensive event for sure.

    Frank a Maritool has always impressed me both with his knowledge base and his willingness to help people on here even when there is no business incentive to do so. This thread got me thinking I might be pushing my facemill a bit aggressively, so I will rethink my strategy and probably drop down to a 1" facemill going fast, rather than a larger facemill that loads the spindle.

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    Quote Originally Posted by wheelieking71 View Post
    I don't have dual contact. I was talked out of it by the salesman. I was stupid for listening to him.
    If you're busy enough now so can afford it, i'd swap the spindle out ASAP for a BBT.
    Buy a new BBT facemill holder, and some roughing sidelocks to cover the bigger sizes (14mm, 12mm, 10mm) and that will do for most of it.
    Then crank the feedrates right up

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    I took an old long BT-40 coolant through stud, clamped it in a pipe vise, and beat on it with a 2 pound ball peen hammer for several minutes. It marred but did not break or bend. I dismounted one of the other Maritool studs and it fractured in the same way as the one out of the machine with a fairly light strike. We are going to do some more later today and put it up on Youtube so everyone can see how they are failing.

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    Quote Originally Posted by barbter View Post
    If you're busy enough now so can afford it, i'd swap the spindle out ASAP for a BBT.
    Buy a new BBT facemill holder, and some roughing sidelocks to cover the bigger sizes (14mm, 12mm, 10mm) and that will do for most of it.
    Then crank the feedrates right up
    I was wondering if BBT could be swapped in. I guess so huh?
    I do have TSC/tool-wash already. So, it is just a matter of swapping the cartridge?
    What about holders. Can non-BBT holders be used in BBT spindle?

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    Quote Originally Posted by cnctoolcat View Post
    I would definitely go with a high-strength pull stud of whatever brand for a 30-taper machine.

    And as far as the ultimate strength goes --- from a machining standpoint, a pull stud that has been finish ground on the neck and related radii and shoulders will be stronger than one that is just finish turned.

    Why?

    Finish turning leaves the spiral "hills and valleys" around the circumference of the part, with the valleys potentially creating a stress riser, especially near a corner or beginning of a radius.
    Keep the effective feed rate well under half the nose radius of the tool and you shouldn't have any "hills and valleys"....theoretically. Hard turning can produce finishes in the same range as grinding. Grinding can achieve a better finish for sure but not by much, and certainly not significant relative to the dents left by the retention balls.

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    Quote Originally Posted by Mickey_D View Post
    I took an old long BT-40 coolant through stud, clamped it in a pipe vise, and beat on it with a 2 pound ball peen hammer for several minutes. It marred but did not break or bend. I dismounted one of the other Maritool studs and it fractured in the same way as the one out of the machine with a fairly light strike. We are going to do some more later today and put it up on Youtube so everyone can see how they are failing.
    Do you have any non-Maritool 30 taper pull studs you can hit in the same manner? If you're going this far you might want to hack together a Charpy(ish) pendulum tester to get consistent impact loads.

    YouTube

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    Quote Originally Posted by wheelieking71 View Post
    I was wondering if BBT could be swapped in. I guess so huh?
    I do have TSC/tool-wash already. So, it is just a matter of swapping the cartridge?
    What about holders. Can non-BBT holders be used in BBT spindle?
    I'm no expert for Brothers - but for Robos or the Feelers (any cartridge spindle as far as i know) you can just swap them out.
    Standard BT30 and BT40 have a 2mm gap - flange of holder to face of spindle (BT50 is 3mm).
    A BBT spindle has (roughly) 1mm added to the face.
    And a BBT holder has the same added to the flange (hence they touch).
    So you can run standard holders in a BBT spindle, and there will be a 1mm gap (because the standard holder has the thinner flange).

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    Quote Originally Posted by Milland View Post
    Do you have any non-Maritool 30 taper pull studs you can hit in the same manner? If you're going this far you might want to hack together a Charpy(ish) pendulum tester to get consistent impact loads.

    YouTube
    A piece of string looped and tied over a rafter in the ceiling with a weight tied to the end of it. Then position the bench under it, and use a rule to measure the swingback distance of your weight for consistency.
    If you want to try like-for-like testing...

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    I know it would be more money because of tooling cost and then work holding/machining, but does anyone make pull studs from forgings?
    I always thought that maybe a good way to go because you can then have the grain the way you want it?

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    Quote Originally Posted by Mickey_D View Post
    I took an old long BT-40 coolant through stud, clamped it in a pipe vise, and beat on it with a 2 pound ball peen hammer for several minutes. It marred but did not break or bend. I dismounted one of the other Maritool studs and it fractured in the same way as the one out of the machine with a fairly light strike. We are going to do some more later today and put it up on Youtube so everyone can see how they are failing.
    Little reliable data is obtained with a thumb detector. Also that is applying radial load which would be far more reliable to do with a long bar, pull gauge and some math.

    I would be far more interested in seeing the ultimate tensile strength, yield, elongation, exc. AKA it needs to be yanked to failure while recording the data. Once upon a time I had access to such equipment.

  19. #76
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    Quote Originally Posted by Mickey_D View Post
    That is the only stud that has marks like that and they probably came from being flung around inside the retainer. The other ones that we got from Maritool and Yamazen all look virtually new.
    The forces from being "flung around" won't be as high as the forces from normal drawbar retention. The pull stud had to be intact to create those indents. It looks like something went wrong with the workholding or cutter during the cut, which tried to pry the tool out of the spindle. That formed the indents and, with continued prying, the pull stud neck broke due to overload. When it broke, the taper was already unseated and the indents were already formed. You could bound the force it took to break the stud by using finite element modeling to model the indent formation. It would be a nice research project for a PhD-type, but not cheap.

    Is it possible the insert that was embedded in the workpiece had not been seated or torqued properly after the last index or replacement? It is not that difficult to get an insert cockeyed while the screw still has the right torque. I have caught an operator doing it.

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    Quote Originally Posted by rklopp View Post
    It is not that difficult to get an insert cockeyed while the screw still has the right torque. I have caught an operator doing it.
    It's also not unheard of for the screw to just fail, especially if they are not torqued (without the correct torque driver, practically everyone overtightens insert screws)

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  22. #78
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    Quote Originally Posted by Milland View Post
    Do you have any non-Maritool 30 taper pull studs you can hit in the same manner? If you're going this far you might want to hack together a Charpy(ish) pendulum tester to get consistent impact loads.

    YouTube
    Spent many hours on one of those breaking all kinds of steels at 'Uni" (back in the day).

    @Milland thanks posting that link earlier about pull studs.


    Really dumb question here :

    1. Do these pull studs work harden through use ? *



    If the answer is YES,

    Then the pull stud you buy is not the same as the pull stud after many thousands of cycles of use.

    IF narrow diameter pull stud work hardens then it means it's tensile yield strength goes up, BUT the material becomes less elastic, less ductile , essentially more brittle. Which means when it does fail and "They do fail" it will fail in a more catastrophic way under higher loads.


    so...

    2. How often should one be replacing one's pull studs on a 30 taper machine , before they fail ?

    3. Also kinda interested in the materials science between the cheap pull studs vs. the more expensive ones ?

    I'm not part of the 30 taper taper- mafia but have always been BBT 30 taper "Curios" ;-)


    __________________________________________________ __________________________________________________ _________________

    * the metallic structure of the piece will change through use... so the one you buy NEW is not the same as the one you have been using for x-thousands of cycles under high loads.

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    Quote Originally Posted by Mickey_D View Post
    I took an old long BT-40 coolant through stud, clamped it in a pipe vise, and beat on it with a 2 pound ball peen hammer for several minutes. It marred but did not break or bend. I dismounted one of the other Maritool studs and it fractured in the same way as the one out of the machine with a fairly light strike. We are going to do some more later today and put it up on Youtube so everyone can see how they are failing.
    Your kidding right?

    Your conducting a very unscientific test, which bears no relationship to the type of load seen by a pull stud and then post it on youtube?

    I can't see how anybody could get anything usefull by wacking a BT40 stud then a 30 taper stud and draw an intelligent conclusion.

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    Quote Originally Posted by wheelieking71 View Post
    I was wondering if BBT could be swapped in. I guess so huh?
    I do have TSC/tool-wash already. So, it is just a matter of swapping the cartridge?
    What about holders. Can non-BBT holders be used in BBT spindle?
    You can use Non BBT in the BBT spindle. We can change the spindle but you need to have face wash, which you might have. We would have to check. If you have face wash than I would wait until you need a spindle and then change to BBT. If you don't have face wash, then we would have to add that. R650 currently comes standard with face wash but I don't think they started that way.


    Andy


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