Problems with 5th Axis Pull-Studs
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  1. #1
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    Default Problems with 5th Axis Pull-Studs

    We have quite a few fixtures, bases, risers, etc from 5th Axis in our shop. We use them in a lot of our machines, and in inspection as well. Recently we've been noticing a lot of these pull-studs breaking. Some are breaking at the pull stud itself, some are breaking the actual stud/set screw that threads into the base/pullstud. I would say we've had close to 2 dozen of them break. We are using a torque wrench on all of them, and I'm not sure what the problem could be. I'm not jumping to 5th Axis being the problem, but it does seem like a bad heat treat batch or something like that.

    Has anyone else seen this??

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    Post pics of the broken ends of the studs, along with used but unbroken pieces. Make them as large and clear as you can, if you have issues, use an external pic server and post links.

    And give 5th Axis a call tomorrow and get their thoughts.

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    Heat treat embrittlement is a legitimate possibility, not exactly a common thing though. I've heard of CAT pullstuds shattering because they were improperly heat treated. That's an expensive oopsie.

    I would reach out to their applications team even if it isnt their fault, they can offer some usage advice.

    I sheared off the truck bolts on my 5th axis unit once because I torqued the lead screw to the max recommended usage level...the jaws got so tight around my part that the bolts holding the jaws to the trucks broke in half. Didn't expect the max torque value to be the failure value lol.

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    I had 1 break a few months ago.
    It had some corrosion on it, but the coolant in that machine was a little suspect.

    Snapped clean in the middle of the V pull groove.

  5. #5
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    Quote Originally Posted by Milland View Post
    Post pics of the broken ends of the studs, along with used but unbroken pieces. Make them as large and clear as you can, if you have issues, use an external pic server and post links.

    And give 5th Axis a call tomorrow and get their thoughts.
    . Will do tomorrow. We did contact 5th Axis, and our tooling distributor. 5th axis says they'll replace them, and they want us to send the pieces to them. They also said they've never seen the problem before. But I find that a little hard to believe, considering the amount of them that we've seen broken.

    Quote Originally Posted by metalmadness View Post
    Heat treat embrittlement is a legitimate possibility, not exactly a common thing though. I've heard of CAT pullstuds shattering because they were improperly heat treated. That's an expensive oopsie.
    We considered this. Maybe heat treated, but not tempered or something like that? I did notice that the pull studs are coming in different colors. Some are grey, while some have more of a brown/copperish color.

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    Quote Originally Posted by Milland View Post
    Post pics of the broken ends of the studs, along with used but unbroken pieces. Make them as large and clear as you can, if you have issues, use an external pic server and post links.

    And give 5th Axis a call tomorrow and get their thoughts.
    Hopefully this link works. The broken retention knob, and the broken threaded stud were 2 separate instances. Different fixtures, different pullstuds, different machines.

    5th Axis - Google Photos

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    Hmm - I'm not a metallurgist (did take a class in HS), but looking at the last pic with the female threaded part that split, to me it looks like a flaw or crack near the inside propagated outwards until the whole thing failed. Like some stress associated with the female thread lead to a crack at the root, then it spread.

    The broken male threads are a little harder for me to read, more like it's a simpler tensile failure, maybe starting with some bending. Is that rust on the outside of the threads? Is coolant chemistry not being kept up? Check for corrosion products.

    You're using a torque wrench, has it been calibrated, and are the numbers what 5X recommends? Try backing off a bit, not everything has to be at max. Or, is the operator giving it a little extra tug after the torque indicator goes off?

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    Quote Originally Posted by Milland View Post
    Hmm - I'm not a metallurgist (did take a class in HS), but looking at the last pic with the female threaded part that split, to me it looks like a flaw or crack near the inside propagated outwards until the whole thing failed. Like some stress associated with the female thread lead to a crack at the root, then it spread.

    The broken male threads are a little harder for me to read, more like it's a simpler tensile failure, maybe starting with some bending. Is that rust on the outside of the threads? Is coolant chemistry not being kept up? Check for corrosion products.

    You're using a torque wrench, has it been calibrated, and are the numbers what 5X recommends? Try backing off a bit, not everything has to be at max. Or, is the operator giving it a little extra tug after the torque indicator goes off?
    What appears to be rust is actually copper anti-seize (which, IIRC, 5th Axis supplies with the kits) The torque wrenches are almost brand new, and everything in the shop is calibrated routinely as far as measuring equipment, torque wrenches, etc.

    5th Axis designates a value of 30ft/lbs. Not a max value. We have actually asked that question as well. We will see what they say regarding the torque.


    As far as if the operators are all torqueing correctly with no extra ugga-duggas, as I'm sure you know, that's hard to say.

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    30ft-lbs is decent. I tighten my retention knobs to 45 for CAT40...Techniks says you can do 75, but ive seen bellmouthing from that . I would think a pull stud that big should have zero issues with 30 ft lbs...especially if its properly heat treated.

    If the quenching cycle is off and it doesn't get properly tempered itll be brittle. But IDK if that can really be because it has happened alot you say. All studs from the same batch?

    I am inclined to suggest operator error but, many factors here. Definitely want to have them demonstrate their process in front of you to make sure there are no mistakes

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    Quote Originally Posted by metalmadness View Post
    30ft-lbs is decent. I tighten my retention knobs to 45 for CAT40...Techniks says you can do 75, but ive seen bellmouthing from that . I would think a pull stud that big should have zero issues with 30 ft lbs...especially if its properly heat treated.

    If the quenching cycle is off and it doesn't get properly tempered itll be brittle. But IDK if that can really be because it has happened alot you say. All studs from the same batch?

    I am inclined to suggest operator error but, many factors here. Definitely want to have them demonstrate their process in front of you to make sure there are no mistakes
    We do check from time to time, when setting a job up, to make sure the torque wrenches are still set the same, and occasionally we will check to make sure the bases aren't overly tight, but it's honestly hard to say if that's always the case. I don't believe they'd have been from the same batch, as they were purchased over a period of 6 months to a year. Not sure when the broken studs were purchased exactly. I believe we are going to take a handful of the unbroken USED parts, and a handful of the NEW parts and send them out for LPI testing. Some of the operations these are used on could cause some major major damage if they were to come out during a roughing operation. I honestly hope that operator error is at fault, as I like 5th Axis stuff.

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    "They also said they've never seen the problem before. But I find that a little hard to believe, considering the amount of them that we've seen broken."

    That's what Mastercam always says when you ask the rep about bugs, even when several people on their site reported the same issues for months or years.

  12. Likes mhajicek, SRT Mike liked this post
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    Update; 5th Axis is sending us 20 new studs, and gave us a procedure as to how they want the pull-studs installed, which is admittedly less torque than I'm sure we were installing the pull-studs with. We will make sure we are torqueing them as they request, and hopefully the problem goes away.

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    On the internal thread failure, was the external threaded stud very tight into the pull stud? If it was tightened into the blind tapped hole in the stud, the thread in the bottom of the hole would see a ton of tension in the first root, where it looks like the crack started. Not sure about the external thread failure, maybe that was a secondary failure. see the picture below from their catalog.

    screenshot-2021-05-14-154842.jpg

    On the torque, since they specified torque and the use of anti seize, there may have been an oversight on torque spec and tension on their part. Fastener torque calcs usually assume oiled threads so using anti seize that decreases thread friction will ramp the tension way up as a particular torque. Also changing types of anti seize can have a big friction change, especially those containing molybdenum disulfide.

    good luck with resolving it

    Mike


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