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    Quote Originally Posted by lowCountryCamo View Post
    The studs on our Okuma cat40's are short and fat. I like them. Unlike the studs on my Yang cat40 in my garage which is long and thin. The Haas cat40's at work are same as mine. I have often wondered why a spindle manufacturer would choose the long skinny type?
    Attachment 269589Attachment 269590
    Cheaper keeper. The finger type retainers are more $$$$ than ball and cages. At least that is my guess. Ball and cages need more room so no stubby retention knobs for them.

    Come to think of it are not Fadal knobs like the one on the left? And I know the one I worked with had balls and a cage. Maybe my guess is wrong.

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    Quote Originally Posted by Vancbiker View Post
    Had a customer in the mid 80s with a couple Brother TC221 machines. Really just drill/tap machines. You could face mill kinda, sorta. Totally conversational control. No CRC. IIRC, no circular interpolation. Anyway, very limited milling functionality. For drilling and tapping though they were superb. Rigid tapping at 4k RPM (maybe 6k, I don't recall for sure) in the mid 80s!
    Those were neat machines for certain jobs at the time. I remember being amazed when I saw my first cnc, anything like that is amazing after running lineshaft machines.
    I'm running anything from 17-4 H900 to plain old 6061, No issues milling, unless I make a mistake. I have 2 dual contact hi-torque machines, and 2 of the standard 10K spindle machine. High speed paths work very well. Cycle times are quite a bit shorter than even my Haas Super Mini Mill, which isn't a slouch. Shorter than my older VF-2 also. Small cutter, moving fast. Smaller cutters are cheaper,uses less juice too. Faster than the Robo I had as well. Fit the tool to the job, and all is well.

    I see that someone posted about breaking 3 Cat40 pull studs - how is that even possible??!! I'm shocked, shocked I tell you!!

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  4. #163
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    I've only worked cat40 machines but I've never seen a broken pull stud. And I've seen some dumbass moves.

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    Quote Originally Posted by lowCountryCamo View Post
    The studs on our Okuma cat40's are short and fat. I like them. Unlike the studs on my Yang cat40 in my garage which is long and thin. The Haas cat40's at work are same as mine. I have often wondered why a spindle manufacturer would choose the long skinny type?
    Attachment 269589Attachment 269590
    Because in this application there is almost no difference in strength. Pull studs are in pure tension until things are going wrong and in pure tension they’re the same strength and one has more room for design flexibility.

    30 taper pull stud is smaller than an R8 drawbar, you have to expect some limitations. Highly doubt anything material wrong with this stud. It wouldn’t have made it the 6 months it did.

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    Well heck - if a 5/16 neck is as strong in tension as a 1/2" rod, then I just don't know why on Earth I made 3" tie bars for that steam powered steel mill project over in Youngstown!

    For Petey's sakes - he could have just updated to 3/8 and been done with it.
    But, I guess he prolly wanted to keep it original - if only to show the waste of bygone days?




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    Quote Originally Posted by JCByrd24 View Post
    Highly doubt anything material wrong with this stud. It wouldn’t have made it the 6 months it did.
    You make a really good point. I never thought of it that way.

    I had 3 break (haas vf2ss cat 40) 2 on threads 1 in the middle . one thread and the broken middle one broke while just sitting in spindle luckly after I put in tool holder. the other one with the bad thread broke while tighting it.
    all three of those had marks that showed they were cracked along time prior. the one I was tighting that cracked was new on a new cat 40 holder. even the black anodized was in 20-30% of the broken section. all from the same time we bought machine 5 years prior. bought 30 new ones that week. ours were kenmetal.

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    Quote Originally Posted by lowCountryCamo View Post
    The studs on our Okuma cat40's are short and fat. I like them. Unlike the studs on my Yang cat40 in my garage which is long and thin. The Haas cat40's at work are same as mine. I have often wondered why a spindle manufacturer would choose the long skinny type?
    Attachment 269589Attachment 269590
    I agree! I love the short and fat fadal/mazak/okuma style. And Im still paranoid about one breaking for some reason even though this is probably the strongest style pull stud. Fadal uses ball bearing type drawbar. The bearings do tend to mark the pull studs over time versus the finger type on mazaks, but seem to work fine otherwise.

    Maybe the 30 taper spindles are fine with proper speeds/feeds/tools but no matter what you guys say, the pull stud is definitely one of the weakest points on these machines. And I dont think it would take a whole lot of effort for them to make an improved, much stronger system over the BT30 without adding a ton of weight.

    Id still have a hard time spending my money on a 30 taper machine after hearing so much talk about these pull stud problems.

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    Quote Originally Posted by mmurray70 View Post
    I agree! I love the short and fat fadal/mazak/okuma style. And Im still paranoid about one breaking for some reason even though this is probably the strongest style pull stud. Fadal uses ball bearing type drawbar. The bearings do tend to mark the pull studs over time versus the finger type on mazaks, but seem to work fine otherwise.

    Maybe the 30 taper spindles are fine with proper speeds/feeds/tools but no matter what you guys say, the pull stud is definitely one of the weakest points on these machines. And I dont think it would take a whole lot of effort for them to make an improved, much stronger system over the BT30 without adding a ton of weight.

    Id still have a hard time spending my money on a 30 taper machine after hearing so much talk about these pull stud problems.

    You know what, there are more than one style of pull stud for 30 taper tools, kinda like there is with 40 taper tools. Some are bigger than others and therefore stronger. Nothing wrong with the 30 taper format.

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    Quote Originally Posted by DavidScott View Post
    Nothing wrong with the 30 taper format.
    In general, I agree. But on the specifics, there can be surprises for those used to larger spindle tapers. The combination of lighter drawbar retention force and smaller stem diameter means the margin between "safe" and "risky" on tooling size and S/F becomes smaller.

    I think Frank's proposed Super-stud, as well as a revised suggestion sheet for tooling and S/F are good starts to "calming the waters".

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    True 30 taper is not 40. Projection is EVERYTHING with 30 taper. That 2" face mill the op lost would be about like a 3" in a 40 taper machine, pretty safe, but a lot of projection.

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    Quote Originally Posted by DavidScott View Post
    You know what, there are more than one style of pull stud for 30 taper tools, kinda like there is with 40 taper tools. Some are bigger than others and therefore stronger. Nothing wrong with the 30 taper format.
    Until someone tries to do 40 taper things

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    Quote Originally Posted by JCByrd24 View Post
    Because in this application there is almost no difference in strength. Pull studs are in pure tension until things are going wrong and in pure tension they’re the same strength and one has more room for design flexibility.

    30 taper pull stud is smaller than an R8 drawbar, you have to expect some limitations. Highly doubt anything material wrong with this stud. It wouldn’t have made it the 6 months it did.
    There is more difference than the length in the 2 studs I pictured. Look at the Dia. Look at the nice Rad on the short fat stud.

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    Quote Originally Posted by lowCountryCamo View Post
    The studs on our Okuma cat40's are short and fat. I like them. Unlike the studs on my Yang cat40 in my garage which is long and thin. The Haas cat40's at work are same as mine. I have often wondered why a spindle manufacturer would choose the long skinny type?
    Attachment 269589Attachment 269590
    The short Pull stud looks suspiciously like a Fadal pull stud, the longer one looks like a pull stud I use on my Makino.

    There is a big difference in the spindle tapers between my Fadals and my Makino RMC55.

    The floater, the part that retains the balls on a Fadal is installed from the bottom of the spindle, and due to it's diameter, the taper in the spindle is shorter than the taper on the toolholder, therefore the toolholder gets less support than it would have as the taper in the spindle is not long as the taper of the toolholder.

    On the Makino, the part that retains the tool is installed from the top of the spindle. So the taper in the spindle is as long as the taper on the toolholder. So that's why the pull stud is much longer than the Fadal pull stud.

    I don't mix Fadal/makino toolholders. It's immediately apparent on a fadal toolholder where the taper on the spindle stops. Not on a Makino toolholder.

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    Quote Originally Posted by lowCountryCamo View Post
    There is more difference than the length in the 2 studs I pictured. Look at the Dia. Look at the nice Rad on the short fat stud.

    I just measured a short/fat one @ about .490 (no idea what it's for) and a skinny one (My Hardinge (Yang) mills) at .390 (I have some for old Cinci @ .410 too)

    So that's the diff between .120 and .190 sqr inch mass.
    Now take away an 1/8" coolant hole and you git .108 and .178, making the short/fat 2/3 aggin stronger.


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    Quote Originally Posted by plastikdreams View Post
    I've only worked cat40 machines but I've never seen a broken pull stud. And I've seen some dumbass moves.
    When my cat40 tool came out all was intact. Except the enclosure where it hit. And spindle bore needed some love along with a drive lug.

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    I've been running the same long skinny pull-studs on my Makino since 1995. I have close to 2000# retention force.

    Probably should replace them I guess. I'll get some more from Mari-tool nexr time I order some endmills.

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    Something you armchair metallurgists etc seem to miss is that the stress on the pull stud is 11'733psi for a retention force of 700#

    So if a pull stud was a thru hardening steel with a strength of 200ksi, the factor of safety would be 200'000psi/11'733psi = 17.

    That stud didn't just fail on it's own. It wasn't a fault of the heat treatment or surface finish or even excessive hardness.

    The fact that the retention balls left indentations in the head of the pull stud would suggest the stud is not excessively hard.

    That pull stud broke because the toolholder was trying to pull itself out of the spindle. At some point the OP should fess up to what really happened or delete the thread.

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    Quote Originally Posted by triumph406 View Post
    Something you armchair metallurgists etc seem to miss is that the stress on the pull stud is 11'733psi for a retention force of 700#

    So if a pull stud was a thru hardening steel with a strength of 200ksi, the factor of safety would be 200'000psi/11'733psi = 17.

    That stud didn't just fail on it's own. It wasn't a fault of the heat treatment or surface finish or even excessive hardness.

    The fact that the retention balls left indentations in the head of the pull stud would suggest the stud is not excessively hard.

    That pull stud broke because the toolholder was trying to pull itself out of the spindle. At some point the OP should fess up to what really happened or delete the thread.

    The stud linked to previously shows to have a .293" neck diameter = .067 sqr inch.
    200K x .067 = 13,400# rating. (PSI not used here)

    I don't understand quite where your 11,733 comes from?


    And BTW, I'm at my desk in the shop.


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    Quote Originally Posted by Ox View Post
    The stud linked to previously shows to have a .293" neck diameter = .067 sqr inch.
    200K x .067 = 13,400# rating. (PSI not used here)

    I don't understand quite where your 11,733 comes from?


    And BTW, I'm at my desk in the shop.


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    The neck on the BT30 pull stud is 7mm dia = .2755"

    area = (.2755/2)*(.2755/2) * pi = .0596in^2

    tensile stress = Force /area

    If BT30 retention force is 700#

    tensile stress = 700# / .0596in^2 = 11733.4psi

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    A long time ago a PM thread I started was deleted because the title questioned if a popular machine tool builder’s “economy line” was any good. I thought it was a fair topic for others that may be wondering the same thing but I’m over it. I’m surprised this thread, especially with how active and popular Frank is here, has not been renamed to something like, “Why did the pull stud on my 30-taper Brother fail?”

    Nevertheless I am impressed how what had started out as something like lawyers arguing their stances in an effort to assign guilt has evolved, thanks to the community, to more of something like a deliberation by a panel of jurors analyzing the evidence to come to a reasonable conclusion. I know I’VE been sniffing around the pull studs at my shop more the past couple of days! Bravo!

    FWIW if I walked in on a Speedio where the tool has fallen out, the stud had broke, and the part had moved in the vice my initial thought would be, “uh oh, part slipped!” Maybe I’m wrong but I suppose I’ve just had an infinite number more of parts run away on me than pull studs that have broken. I had a tool get yanked out of a Brother S2Dn but that was because the part lifted up so the profiling em helix pulled it right out. The stud was fine. Of course the tool danced around in the taper and made a mess but a little emory cloth and a lot of elbow grease fixed it up pretty good! Haha.

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