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    Quote Originally Posted by DavidScott View Post
    Ok, this got me to thinking. My theory to what happened is the tool holder was pulled out of the spindle a little allowing a SIDE LOAD on the pull stud which is what broke it. With the tool holder partially pulled out of the spindle it will roll around the taper as it pushes against the workpiece while the pull stud is held to the center of the spindle by the drawbar. This flex on the pull stud would certainly be hard on it and cause it to fail where it did vs popping the head off. It would also explain the deep divots from the balls. This theory would also explain why pull studs in dual contact spindles hold up longer, if that is true, even though they are under much more tension from more drawbar force.
    Exactly ^^^^^^^

    Quote Originally Posted by DavidScott View Post
    Mickey_D where are you? You started this shit throwing then left, what's up?
    Almost like he started investigating a little deeper and realized: "ohh shit!"

    I would like to see the drive coupling above the spindle. I bet its toast. Because I also bet that the tools rotation stopped very abruptly when it hit that part that was loaded wrong.

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    Quote Originally Posted by DavidScott View Post
    Ok, this got me to thinking. My theory to what happened is the tool holder was pulled out of the spindle a little allowing a SIDE LOAD on the pull stud which is what broke it. With the tool holder partially pulled out of the spindle it will roll around the taper as it pushes against the workpiece while the pull stud is held to the center of the spindle by the drawbar. This flex on the pull stud would certainly be hard on it and cause it to fail where it did vs popping the head off. It would also explain the deep divots from the balls. This theory would also explain why pull studs in dual contact spindles hold up longer, if that is true, even though they are under much more tension from more drawbar force.
    Of course something else happened, the pullstud did not "just break". Heck, an aluminum pullstud would not have broken, at the nominal drawbar tension, without something else going on. 6061 is good for 30 kSI, 1018 mild steel 55 kSI. In the nominal locked-in straight-pull configuration, the pullstud neck in a Brother is seeing 12-15 kSI.

    Regards.

    Mike

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    Default Cheap knobs vs. expensive "Knobs" + various distortions

    Quality Retention Knobs Are Vital For Safety And Performance

    ^^^^ Haimer explains the difference in materials and form and types of heat treat and what can happen here cheap versus high quality ^^^ (Probably most of you here know this stuff) ~ might add some notes later/ quick cheat sheet.


    The Knob Problem :


    Modern Machine Shop


    "The Knob Problem" ^^^ Modern Machine shop + J&M / John Wayne Stoneback in 2009 discussing the distortion problem from over torqueing cheap knobs... There's some really interesting graphs for tool holder deformation... Interestingly Frank Mari has the same testers for measuring conformity for a tool holder.

    Later on today I'll tease out notes and diagrams and various dynamics (If need be).

    __________________________________________________ __________________________________________


    In MickeyD's case IF he over torques a cheap retention knob (knowing he's taking things to the limit) then this will cause the tool holder to distort.

    IF --> (this gets a bit iffy with all the if's).

    IF the tool holder is distorted (fatter in cross section at the narrow end) then the tool holder will not fit in the spindle nose receptacle / socket properly.

    Stoneback refers to this phenomenon much like a "clapper in a bell". (see the article above).


    With substantial bending moments (especially with added tool bending moments from an aggressive cut) and ill fit of the tool holder and ill fitting retention knob AND consequent deformation of the spindle receptacle it seems pretty likely even from a 5 to 10 micron misalignment from various static and dynamic distortions that the neck of the retention knob is being flexed... Tight interspace for fingers or the balls when the draw bar is pulled up... I.e. the rotational axis of the tool holder and the axis of pull stud are not colinear causing fatigue at the neck of the pull stud .

    The leverage of this misalignment could be very considerable indeed* .

    Looking at MickeyD's facture (early shots) you see this V or cone like depression of the fracture surface into the body of the thread of the pull stud. To me that's indicative of failure due to being flexed repeatedly.

    __________________________________________________ ___________________


    * Take an old fashioned high nickel content serving spoon and try and pull into to two by stretching with your bear hands... extremely difficult. But make very tiny flexions almost imperceptibly and repeatedly within a few hundred cycles or less you can go all Uri Geller and snap the spoon.

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    Quote Originally Posted by DavidScott View Post
    Ok, this got me to thinking. My theory to what happened is the tool holder was pulled out of the spindle a little allowing a SIDE LOAD on the pull stud which is what broke it. With the tool holder partially pulled out of the spindle it will roll around the taper as it pushes against the workpiece while the pull stud is held to the center of the spindle by the drawbar. This flex on the pull stud would certainly be hard on it and cause it to fail where it did vs popping the head off. It would also explain the deep divots from the balls. This theory would also explain why pull studs in dual contact spindles hold up longer, if that is true, even though they are under much more tension from more drawbar force.

    Mickey_D where are you? You started this shit throwing then left, what's up?
    That's funny you beat me to it by 30 seconds …

    Ditto "Flexing"

    + materials

    __________________________________________________ _______________________________


    I think with the back of fourth with Frank Mari and Mickey_D, Mickey_D seems to acknowledge that he probably should have bought the expensive pull studs but Mickey_D's more current 'Beef" is that the sales person at Mari Tool should have advised him to purchase the expensive ones ? Frank seems to indicate that Mickey_D should have sought Frank out for advise on this matter in terms of product selection.

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    Quote Originally Posted by cameraman View Post
    That's funny you beat me to it by 30 seconds …

    Ditto "Flexing"

    + materials
    That's a good theory.

    And think about it this way.

    When you bend a paperclip, how many times do you have to bend it back and forth before it snaps?

    If a spindle is moving at 10,000 RPM, is the pull stud bending 10,000 full back and forth cycles per minute? Even over 1 second, that's 166 cycles.

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    Quote Originally Posted by DavidScott View Post
    Ok, this got me to thinking. My theory to what happened is the tool holder was pulled out of the spindle a little allowing a SIDE LOAD on the pull stud which is what broke it. With the tool holder partially pulled out of the spindle it will roll around the taper as it pushes against the workpiece while the pull stud is held to the center of the spindle by the drawbar. This flex on the pull stud would certainly be hard on it and cause it to fail where it did vs popping the head off. It would also explain the deep divots from the balls. This theory would also explain why pull studs in dual contact spindles hold up longer, if that is true, even though they are under much more tension from more drawbar force.

    Mickey_D where are you? You started this shit throwing then left, what's up?
    100% agree.
    Well worded.

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    Quote Originally Posted by 2outof3 View Post
    As I stated earlier, I am very proud of the group of Brother users on this forum but we are starting to leave the impression that this pull stud breaking is an expected out come if you buy a Brother. Thousands of machines leave the factory every year. Brother has built over 150,000 verticals so far. This is a bit of a phenomenon here in the US to those aggressive Americanos who want to get every bit out of their machines. 10 years ago when I started working with the Brother product, we had one customer who started going through spindles on the TC-S2 product. He was welding end mills in the same spot of his program or lifting a part that was being face milled in an older aluminum set of jaws. The weak point was always the pull stud first. We finally got him to change some of his attacks on his part and he bought a Speedio with dual contact and that extra bit of support changed things for him.

    Koenig said it earlier. Most of these failures are users who are pushing and making the transition from 40 taper to 30 taper. The majority of machines we sell never see this failure. A bit of this phenomenon goes back to the old way of proving programs. Push the machine until you break the end mill and back off ten percent. A very American approach. We have done this in our own showroom. We are working on the cutter database and approach for our own use but there is a need to make something that is on an open forum.

    Yes your spot on Andy ,, we are aggressive Americans that want to get ever bit out of are machines .. if we don`t are competitors well. Brothers has a good product but its looking to me at least that they need to look at there pull studs closer and make it so its not the "FUSE"
    Brothers had done some really great things in making a small drill/tap machine into a full on small mill . But one really has to shake there head as to why someone would build a heavier machine and give it more power and make it smoking fast only to retain a small pull stud and make it the weak link ...

    Even you just wrote about it "The weak point was always the pull stud first" like I posted a couple days ago ... I have 37+ years in running cnc mills and have never seen a machine that used the pull stud as the weak link before ,, And yes I am one of them "aggressive Americans that pushes tools tell they snap then back off 20% ...

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    Quote Originally Posted by D.D.Machine View Post
    Yes your spot on Andy ,, we are aggressive Americans that want to get ever bit out of are machines .. if we don`t are competitors well. Brothers has a good product but its looking to me at least that they need to look at there pull studs closer and make it so its not the "FUSE"
    Brothers had done some really great things in making a small drill/tap machine into a full on small mill . But one really has to shake there head as to why someone would build a heavier machine and give it more power and make it smoking fast only to retain a small pull stud and make it the weak link ...

    Even you just wrote about it "The weak point was always the pull stud first" like I posted a couple days ago ... I have 37+ years in running cnc mills and have never seen a machine that used the pull stud as the weak link before ,, And yes I am one of them "aggressive Americans that pushes tools tell they snap then back off 20% ...
    But that would be a compromise that Brother is not going to do. It is single mindedly engineered to be best at volume production, PERIOD! Trying to do something it was never designed for and bitching that it failed is shortsighted. I am going to guess that more drawbar force is the solution to the pull stud problem, not different pull studs. Maybe an option for those that want it? Maybe a dual contact drawbar option for the standard spindle?

    I SURE WISH drawbar forces could be discussed here, it is pretty relevant. What are they for a standard spindle and a dual contact Speedio?

    Question: Any stories of a pull stud breaking in a dual contact Brother, or other 30 taper mill?

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    Quote Originally Posted by DavidScott View Post
    Ok, this got me to thinking. My theory to what happened is the tool holder was pulled out of the spindle a little allowing a SIDE LOAD on the pull stud which is what broke it. With the tool holder partially pulled out of the spindle it will roll around the taper as it pushes against the workpiece while the pull stud is held to the center of the spindle by the drawbar. This flex on the pull stud would certainly be hard on it and cause it to fail where it did vs popping the head off. It would also explain the deep divots from the balls. This theory would also explain why pull studs in dual contact spindles hold up longer, if that is true, even though they are under much more tension from more drawbar force.
    Yup. And as the broken pull stud end contacts the spindle ID it scores the crap out of it, ruining the spindle.

    Dual contact also allows more surface face to stop the levering effect that happens earlier in the process with a non dual contact. Of the levering effect is what breaks the pull stud.

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    Quote Originally Posted by 2outof3 View Post
    Of the levering effect is what breaks the pull stud.
    How certain are you of that?

    Can you at least tell us the percentage difference in drawbar force between the two spindles?

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    Quote Originally Posted by D.D.Machine View Post
    Yes your spot on Andy ,, we are aggressive Americans that want to get ever bit out of are machines .. if we don`t are competitors well. Brothers has a good product but its looking to me at least that they need to look at there pull studs closer and make it so its not the "FUSE"
    Brothers had done some really great things in making a small drill/tap machine into a full on small mill . But one really has to shake there head as to why someone would build a heavier machine and give it more power and make it smoking fast only to retain a small pull stud and make it the weak link ...

    Even you just wrote about it "The weak point was always the pull stud first" like I posted a couple days ago ... I have 37+ years in running cnc mills and have never seen a machine that used the pull stud as the weak link before ,, And yes I am one of them "aggressive Americans that pushes tools tell they snap then back off 20% ...
    So, you make a choice to spend more time in other parts of your process to get a bit more milling time out of the part. That is your choice. In the end it is about getting the parts out fast compared to spindle cost. The non dual contact Brother can rough easily with a .500 inch rougher at 1.1 depth , 200 IPM federate and .200 step over. This is a no brainer cut. To me, in most parts I see, that takes care of the roughing close to what many do on their 40 taper machines. Those that choose Brother get the advantage of all the other non cutting benefits and the ability to tap accurately very fast.

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    Quote Originally Posted by DavidScott View Post
    How certain are you of that?

    Can you at least tell us the percentage difference in drawbar force between the two spindles?
    I am certain. The longer the tool, the more likely we see the issue. You just have a whole lot less of comfort with longer tools. This is why BBT is better for long reach tools.

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    Quote Originally Posted by DavidScott View Post

    I SURE WISH drawbar forces could be discussed here, it is pretty relevant. What are they for a standard spindle and a dual contact Speedio?

    Question: Any stories of a pull stud breaking in a dual contact Brother, or other 30 taper mill?
    I have seen a pull stud break on a dual contact. 5 inch long end mill assembly. Hit the part at the bottom and the levering yanked the tool holder out.

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    In my West Coast Yamazen operation, I think this year I have seen almost half as many spindles damaged from over tightened pull studs causing deep fretting as spindles replaced for a broken pull stud and all those broken pull studs were crashes. Maybe 6-8 crashes and 3 or so damaged from pushing the holder out of dimension by over torqueing the pull stud.

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    Many mentions about all the power that these little spindles have - guys wanting to use it all - and the link breaking.
    Then the question - why the link isn't bigger than the motor?

    You guys just aren't thinking this through....

    The reason these machines have so much power / size ratio is Shirley for the point of ramp times.
    Zero to 100mph and back down in 6 feet takes some juice.
    Rigid tapping at the speed of light - takes a lot of spindle hydro to ramp and control - not just computing power.

    You can't hardly have high ramp speeds without a lot of juice to mass ratio.
    If they put a motor more inline with the mass - then you would have old skewl ramp speeds aggin.

    You can't have it both ways....
    You jist need to be aware of the limitations, and know that if you push it past - then it's on you.


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

    Think Snow Eh!
    Ox

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    Quote Originally Posted by 2outof3 View Post
    I have seen a pull stud break on a dual contact. 5 inch long end mill assembly. Hit the part at the bottom and the levering yanked the tool holder out.
    Stuff like that doesn't count. The cause of failure is obvious.

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    Quote Originally Posted by Ox View Post
    Many mentions about all the power that these little spindles have - guys wanting to use it all - and the link breaking.
    Then the question - why the link isn't bigger than the motor?

    You guys just aren't thinking this through....

    The reason these machines have so much power / size ratio is Shirley for the point of ramp times.
    Zero to 100mph and back down in 6 feet takes some juice.
    Rigid tapping at the speed of light - takes a lot of spindle hydro to ramp and control - not just computing power.

    You can't hardly have high ramp speeds without a lot of juice to mass ratio.
    If they put a motor more inline with the mass - then you would have old skewl ramp speeds aggin.

    You can't have it both ways....
    You jist need to be aware of the limitations, and know that if you push it past - then it's on you.


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

    Think Snow Eh!
    Ox
    The HT machine goes from 0-10,000/ stops and goes back to 10,000 in the other direction in about.5 seconds. Yes about half a second. HP, fast communications and great drives and motors are needed for that. When you are changing tools in 1.2 cut to cut, the whole draw bar assembly most work flawlessly and these guys have been doing this for a few decades, always improving. The draw bar is mechanical using a cam system, no pneumatics or hydraulics. It is flawless. Change the draw bar force, pull stud ball and all the other things makes everything else change. Buy it for what it is. It is pretty damn good. Otherwise we would not be talking about it.

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  23. #218
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    Quote Originally Posted by Ox View Post
    Many mentions about all the power that these little spindles have - guys wanting to use it all - and the link breaking.
    Then the question - why the link isn't bigger than the motor?

    You guys just aren't thinking this through....

    The reason these machines have so much power / size ratio is Shirley for the point of ramp times.
    Zero to 100mph and back down in 6 feet takes some juice.
    Rigid tapping at the speed of light - takes a lot of spindle hydro to ramp and control - not just computing power.

    You can't hardly have high ramp speeds without a lot of juice to mass ratio.
    If they put a motor more inline with the mass - then you would have old skewl ramp speeds aggin.

    You can't have it both ways....
    You jist need to be aware of the limitations, and know that if you push it past - then it's on you.


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

    Think Snow Eh!
    Ox
    Ox gets it, and he doesn't even have a dog in the fight!

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    Quote Originally Posted by DavidScott View Post
    Stuff like that doesn't count. The cause of failure is obvious.
    Why does it not count? Go put a 30 taper tool next to a 40 taper tool. Look at the mass and the diameter. The same goes for the spindle and the spindle bearings. It is like using a cheater bar. The farther the tool tip is away from the point of contact, the more leverage it can enforce on the drawbar in an accident.

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    Quote Originally Posted by 2outof3 View Post
    I am certain. The longer the tool, the more likely we see the issue. You just have a whole lot less of comfort with longer tools. This is why BBT is better for long reach tools.
    Andy, why did Greg talk me out of dual contact? What was his reasoning?
    The jist of what I remember was: "it doesn't really add much" "waste of money". (in hindsight, I'm kinda pissed about it really )

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