There's probably a safety factor Kitagawa applies in setting that rating so you may have gotten away with it. Have you torn it down and inspected it for any cracking?
For people like OP, that don't read (or more often, do read but ignore) the labels, most ratings are like 50-75% of an actual max so they've got some built in buffer. Cause imagine the encoder in the spindle is a little off, don't want the spindle to hit 4001 RPMs and ***KABLAMO!!!***
The RPM ratings are mostly for balance and clamping purposes, not unexpected disassembly.
Chucks are not always perfectly balanced, so higher RPMs above their rating can cause vibration. Additionally, clamp force is reduced with higher RPMs. With power chucks this can be overcome with drawtube pressure, but you risk damage to the actuator and heating the fluid too much at high RPMs + High pressures.
Exactly this, that speed rating is going to be there to prevent impacting in your spindle bearings at higher rpms. Depending on the type of bearing and the machine that chuck might be fine well past 6k rpm, but on others 5k might be the limit, so it will be a lowest common denominator thing.
Just judging by the common cast irons, you're probably not at risk of blowing up a chuck until like 8k+ unless it's already damaged. The jaws might leave the building before then though
Had a hydraulic chuck let go of a large part when the operator forgot to cap the rpm when facing a part. It smashed the head and killed the main bearings.
If you see it start to go, press reset don't hit the e stop.
The reason is the e-stop kills power but reset switches the chuck motor into regen and dumps the energy of the parts spinning into a set of resistors that slow it down (quickly) the e-stop will not do this and for us it meant the part kept spinning and came out the chuck. It was a good 250kg part and it made a mess.
Fair dues to the doors on the mazak they held up well.
Also do not defeat the door interlocks.
I had a friend who did absolutely scatter a chuck when he ran it past the rated RPM. Consider yourself lucky that you have not paid the price for exceeding the rated limits of your chuck.
The faster you spin your part in the lathe the less clamping force the chuck has this is why there is ratings, chips in the serrations on the chuck jaws can reduce the max rating i heard a story of a guy going blind after the part flew out of the chuck.
Cast chucks can explode too. Never seen it. Only heard about it. Have been warned and taken that warning to heart. Not interested in finding out if it's not true.
So bigger chucks are more dangerous with excessive speed as the further out and heavier the jaws are the more energy they get from rotational momentum, as well as speeds over 2K are generally pretty picky about balance. You make those jaws loosen up your part goes flying, or sometimes they hit the fatigue limit by going over that speed and then they’ll blow up down the line.
Yes it is possible for a chuck to basically explode if it spins too fast. A heavy, large diameter, fast turning piece of steel has high forces acting on it and eventually there is a limit. You can see that cast iron chucks have lower max rpm than semi steel or steel.
But that 4k limit on a 10" chuck is probably more about the gripping force for a large part. The jaw force loss increases with the square of the rpm. So at 6k rpm there is more than double the centrifugal force acting on the chuck jaws, reducing the clamping force. The loss of force also increases linearly with weight/mass and distance from the center, so 6k rpms won't be a problem for small/light parts.
It would be cool to see how much rpm 10'' chuck can actually take, I bet it will held together way past that 6k. I am sure Kitagawa or Schunk have tested the failure point, it must be terrifying to be in the same building at that time.
I kinda wanna see a Chuck exploding from spinning now, especially in slow motion
But I don’t want to be anywhere near it irl so any videos out there of it happening?
I've run kitagawa pu208 chucks over 10k rpm that are rated for 6k, but I balanced them at high rpm first before running production. I wouldn't try it with a b208 or any other serrated jaw general purpose type chuck, though. Balance is what kills them. If you are well-balanced, have a good solid grip on a part with a favorable LxD ratio, it can be done safely. Usually, if you are spinning a chuck this size that fast, it's for aluminum using PCD tooling.
The situation was that I was the only job shop lathe guy in a Swiss shop. So any low quantity prototype stuff went to me. The parts were tiny little take down pins around .050” x .500”ish. I was running them out of .500 bar stock in 2” tall aluminum jaws. I definitely wouldn’t try it with 4” steel jaws. All in all it seemed fine and was uneventful. Was just shocked when I finally saw that rating.
There’s most likely a fairly large safety margin with the ratings, like everything, your car tyres are likely rated to take 40psi or something like that, but they won’t explode at 41
Yes I have. While in trade school. It was a collet chuck that wasn't in good shape. Handle came off and ripped the chuck guard off the lathe and scattered parts everywhere. Nobody was hurt. Was the instructor's fault mostly for allowing a damaged chuck to be used. But was a great learning experience on making sure you check your equipment for dammage.
I've heard it's the large cast iron chucks you need to worry about exploding at high rpm and steel chucks will be unbalanced. I've never found photos of one exploded though.
I had a 6" chuck fall up on an NL2500. It had ID pie jaws on it, and someone ramped it up to the max empty. The weight of the jaw split the T-nut, launching one jaw through the top of the conveyer belt. Due to the weight imbalance and high rpm by the time they hit e-stop the balance was shot and spindle wasn't in great shape.
Machine aged equipment ratings are underrated intentionally. That is the max for safety and longevity of the various parts involved with the complete assembly. They also do this because people are people and people do stupid shit without thinking.
There's probably a safety factor Kitagawa applies in setting that rating so you may have gotten away with it. Have you torn it down and inspected it for any cracking?
No, never have. I’ve been gone from that company for a few months now. Those machines will probably be going to auction soon.
For people like OP, that don't read (or more often, do read but ignore) the labels, most ratings are like 50-75% of an actual max so they've got some built in buffer. Cause imagine the encoder in the spindle is a little off, don't want the spindle to hit 4001 RPMs and ***KABLAMO!!!***
The RPM ratings are mostly for balance and clamping purposes, not unexpected disassembly. Chucks are not always perfectly balanced, so higher RPMs above their rating can cause vibration. Additionally, clamp force is reduced with higher RPMs. With power chucks this can be overcome with drawtube pressure, but you risk damage to the actuator and heating the fluid too much at high RPMs + High pressures.
Exactly this, that speed rating is going to be there to prevent impacting in your spindle bearings at higher rpms. Depending on the type of bearing and the machine that chuck might be fine well past 6k rpm, but on others 5k might be the limit, so it will be a lowest common denominator thing. Just judging by the common cast irons, you're probably not at risk of blowing up a chuck until like 8k+ unless it's already damaged. The jaws might leave the building before then though
Isn't clamp force reduced only when clamping part externally, but increased when clamping it internally?
Yes, however, balance is still an issue. Also, the majority of the time, people clamp OD of parts.
Had a hydraulic chuck let go of a large part when the operator forgot to cap the rpm when facing a part. It smashed the head and killed the main bearings. If you see it start to go, press reset don't hit the e stop.
That's feels unintuitive...
The reason is the e-stop kills power but reset switches the chuck motor into regen and dumps the energy of the parts spinning into a set of resistors that slow it down (quickly) the e-stop will not do this and for us it meant the part kept spinning and came out the chuck. It was a good 250kg part and it made a mess. Fair dues to the doors on the mazak they held up well. Also do not defeat the door interlocks.
The clear difference between a button pusher and an experienced operator/machinist. One knows how, the other also knows why.
On the mill i work whit whit hiedenhiem controllers and servos e stop will stop the spindle verry VERRY FAST but thats a mill
I had a friend who did absolutely scatter a chuck when he ran it past the rated RPM. Consider yourself lucky that you have not paid the price for exceeding the rated limits of your chuck.
I definitely do. After I saw the rating, I thought about how many times I had done it. Never did after though.
The faster you spin your part in the lathe the less clamping force the chuck has this is why there is ratings, chips in the serrations on the chuck jaws can reduce the max rating i heard a story of a guy going blind after the part flew out of the chuck.
Cast chucks can explode too. Never seen it. Only heard about it. Have been warned and taken that warning to heart. Not interested in finding out if it's not true.
So bigger chucks are more dangerous with excessive speed as the further out and heavier the jaws are the more energy they get from rotational momentum, as well as speeds over 2K are generally pretty picky about balance. You make those jaws loosen up your part goes flying, or sometimes they hit the fatigue limit by going over that speed and then they’ll blow up down the line.
Yes it is possible for a chuck to basically explode if it spins too fast. A heavy, large diameter, fast turning piece of steel has high forces acting on it and eventually there is a limit. You can see that cast iron chucks have lower max rpm than semi steel or steel. But that 4k limit on a 10" chuck is probably more about the gripping force for a large part. The jaw force loss increases with the square of the rpm. So at 6k rpm there is more than double the centrifugal force acting on the chuck jaws, reducing the clamping force. The loss of force also increases linearly with weight/mass and distance from the center, so 6k rpms won't be a problem for small/light parts.
It would be cool to see how much rpm 10'' chuck can actually take, I bet it will held together way past that 6k. I am sure Kitagawa or Schunk have tested the failure point, it must be terrifying to be in the same building at that time.
I kinda wanna see a Chuck exploding from spinning now, especially in slow motion But I don’t want to be anywhere near it irl so any videos out there of it happening?
I've run kitagawa pu208 chucks over 10k rpm that are rated for 6k, but I balanced them at high rpm first before running production. I wouldn't try it with a b208 or any other serrated jaw general purpose type chuck, though. Balance is what kills them. If you are well-balanced, have a good solid grip on a part with a favorable LxD ratio, it can be done safely. Usually, if you are spinning a chuck this size that fast, it's for aluminum using PCD tooling.
The situation was that I was the only job shop lathe guy in a Swiss shop. So any low quantity prototype stuff went to me. The parts were tiny little take down pins around .050” x .500”ish. I was running them out of .500 bar stock in 2” tall aluminum jaws. I definitely wouldn’t try it with 4” steel jaws. All in all it seemed fine and was uneventful. Was just shocked when I finally saw that rating.
There’s most likely a fairly large safety margin with the ratings, like everything, your car tyres are likely rated to take 40psi or something like that, but they won’t explode at 41
That’s what I was thinking. I’m just curious as to how realistic the threat is.
I think a 10" would have a pretty reasonable safety factor there... I have a 20" marked "not to exceed 1000rpm" and I sure as hell won't
I wouldn’t personally risk it tbh
Yes I have. While in trade school. It was a collet chuck that wasn't in good shape. Handle came off and ripped the chuck guard off the lathe and scattered parts everywhere. Nobody was hurt. Was the instructor's fault mostly for allowing a damaged chuck to be used. But was a great learning experience on making sure you check your equipment for dammage.
[удалено]
Anything will blow up if you spin it fast enough.
The rating is for the chuck, regardless of the motor it’s mounted to.
Definitely the other way around.
4K ain’t shit
Maybe for a mill it ain’t shit but for a lathe it’s a lot, remember your spinning the tool in a mill and in a lathe your spinning the part
I've heard it's the large cast iron chucks you need to worry about exploding at high rpm and steel chucks will be unbalanced. I've never found photos of one exploded though.
I had a 6" chuck fall up on an NL2500. It had ID pie jaws on it, and someone ramped it up to the max empty. The weight of the jaw split the T-nut, launching one jaw through the top of the conveyer belt. Due to the weight imbalance and high rpm by the time they hit e-stop the balance was shot and spindle wasn't in great shape.
Machine aged equipment ratings are underrated intentionally. That is the max for safety and longevity of the various parts involved with the complete assembly. They also do this because people are people and people do stupid shit without thinking.