I killed my spindle...
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  1. #1
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    Default I killed my spindle...

    So I was profiling with a .75 endmill and the retention pin snapped off causing my tool holder to fall out and chunk up the spindle seat in the process. img-0877.jpgimg-0878.jpg

    I am assuming I was being too aggressive with the cut. In hind sight I should have done it in multiple depths but with less than 1/6 of the endmill diameter engaged I didn't think it would be that big of a deal in 6061. Pretty pissed though as not only is it going to cost me a ton to fix but it cost me a job too.

    .....

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    That blows.
    Did it take out the bearings, or can you get away with having the spindle re-ground in place?

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    Details about the machine, age of pull stud, and the cut would be mighty handy if you're looking for help in diagnosing the break.

    The down time sucks, but spindle grinding is pretty cheap. Last time for me was about $700, but the guy was already in the area. Still only would have been $1200 (I think) had I had him come out within two days or something like that.

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    Must have been a bad stud.
    Yes, it is tensioned to 1500 kg by drawbar, but it should handle a few tons over it.

    These things fatigue. Sometimes the manufacturer messes up too. We only bought from the machine builder.

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    Note to self: time to order some new pull studs...

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    3/4" tool on a 30 taper is pretty big to do much radial with a long axial engagement. Just for curiosity, how much axial were you running and what speed and feed?

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    Pull stud brand please? In 30 years never had that happen to me.

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    Quote Originally Posted by Kaszub View Post
    Pull stud brand please? In 30 years never had that happen to me.
    Mari tool?

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    Quote Originally Posted by Kaszub View Post
    Pull stud brand please? In 30 years never had that happen to me.
    I've seen the aftermath a few times.

    20K RPM spindle in a wood router with no guards. Tool made a 4 foot long pecker track on the steel frame under the table.

    50 taper 5 axis bridge mill threw a tool through a cinder block wall.

    I'm thinking both operators needed a change of drawers..

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  12. #10
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    .75 diameter end-mills are a total NOGO in a BT30 machine.

    I think the only reason Maritool offers holders above the .5" diameter is to hold funky shank tools (I use one for my Lang chip fan, and another on a slitting saw).

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    Quote Originally Posted by gkoenig View Post
    .75 diameter end-mills are a total NOGO in a BT30 machine.
    I wouldn't say total NOGO but you have to use it within limits. I use a 3/4 all the time in mine in 6061. Mainly cause I got a deal on a batch of 3/4" solid carbides for $35 each.

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    A 3/4 in a BT30 should be an exception for sure in my opinion. A 1/2" rougher can remove up to 90 cubic inches per minute in 6061. Sorry to hear about the mishap gatekeeper. Not sure what caused this but using smaller cutters whenever possible would be my recommendation.

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    It's not so much the tool diameter as it is the length of the tool vs engagement depth IMHO. I've done the same thing, using a 3-3/4" long 50 mm PCD insert end mill. Even though I had the tool designed so that only 1 insert was effectively in the cut at a time, when the inserts got dull and I was mistakenly taking 1/4" WOC x 3" DOC it more or less pushed the tool out of the spindle. Granted - this is on an old S2C, which had much less drawbar pull than the newer machines do. I've also had 2 pull studs break and toast spindles. Ours do production and each tool holder goes through about 500k tool changes a year, so I put in a PM to change them once a year. That is a lot of fatigue cycles on a small pull stud. Fortunately for these instances, spindles for a Brother machine are relatively inexpensive and only take about an hour to change.

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    Quote Originally Posted by Kaszub View Post
    Pull stud brand please? In 30 years never had that happen to me.
    In this case it's indifferent. I think it would happened the same thing with any other brand / manufacturer.

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    I always remind my customers that the stem diameter on a typical BT30 retention knob is just a fraction over 1/4" in diameter. In the past I was responsible for several BT30 machines and after a few pull stud failures we just used 1/2 end mills or smaller. larger only when absolutely needed. Never broke a stud since. Although a 1/2 end mill can cause pull stud failure in a 30 taper spindle it is a little less common.

    What was the gage length on that tool holder?

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  23. #16
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    If it isn't that bad I have lapped them in place before by making something the same angle as the tool holder mating surface out of brass using grinding compound and pushing it up there by hand. Hope you are tech savvy as if you are off the beaten path in this state service calls from private techs are expensive and don't have the greatest reputation.

  24. #17
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    Sorry for not replying sooner. So I had used the .75 because when swapping tools out of one of my collet holders I knocked the .5 endmill off the bench and chipped it. Anyway when I reprogrammed it I got the bright idea of running it with 1.8" axial and .125 radial engagement. I don't remember the feed and speed off hand as I am at my day job but the chips were massive so I was pushing it. The funny thing is when I had it programmed for the .5inch tool I had it set to cut in axial increments. Anyway it wasn't the pull studs fault it was mine.

    Frank - tool holder gauge length was 2.0"

    Dualkit - I had my hand on the stop button since it was the first time running the program outside of a dry run that is so I was able to stop it immediately. I was thinking of possibly lapping it in so good to know others have too.

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    G8KeaPoR,

    If you still have the broken retention knob please send it to us. We would like to send it to our heat treater for a full analysis. It certainly looks like a clear case of just too much load, but I also like to look at faulures regardles. Also include your contact information and we will send you a replacement free of charge and a coupon for your next order. Hopefully that helps soften the blow to your pocketbook.

    Was that our tool holder or someone elses? If it was ours let me know the part number and we will warantee that as well.

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  27. #19
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    I found one of the brass slugs I used to lap with and I believe my machine did use BT-30's. I scrapped the machine and do not need it, let me know, just in case I will send you a private message. If interested I just want postage, unless of course we are neighbors. I will send a PM also.

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  29. #20
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    For what it's worth, I had the same thing happen recently and lost a spindle to it as well. In my case a part pulled out of a clamp and jammed up, the pull stud broke and trashed the spindle taper without it even tripping an axis fault.

    Also a Mari 30 taper (Brother) pull stud, FWIW.


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