It is an issue with hydraulic drawbar closed chucks...most of which have a listed maximum RPM.
Less of a concern with scroll plate chucks.
What's the fastest my spindle can go?
- Bill Shields
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Re: What's the fastest my spindle can go?
Too many things going on to bother listing them.
Re: What's the fastest my spindle can go?
Impossible to answer without knowing the chuck diameter. You'd certainly be in dangerous territory if your chuck measured 36".
Again, without knowing the diameter, a reasonable answer can't be forthcoming.I've heard it said that the centrifugal force on the jaws makes them grip with less force, so a workpiece can come loose. Never experienced that myself, but I'll keep it in mind. Sounds "highly theoretical" (unlikely) at my kinda speeds, agreed?
As far as centrifugal force causing a chuck to release, yeah, that's fact. I've experienced that very thing.
I run an 8" three jaw chuck and use soft jaws routinely. With steel jaws, I've had the experience of a part coming loose when running the chuck @ 2,000 rpm. This is far more likely to happen when a thin item is being chucked without excessive pressure. It's not nearly as likely to happen if your soft jaws are made of aluminum.
H
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: What's the fastest my spindle can go?
Oh right, sorry, 3-jaw is 6", and 4-jaw is 8". I did mention it was a 10" swing lathe, so running a 36" chuck might cause some scraping noises.
Great info, thanks Harold. I do chuck some thin items sometimes, so I'll be mindful. I hope to get into aluminum soft jaws eventually but so far I use the factory-supplied hard steel jaws.Harold_V wrote: ↑Wed Feb 09, 2022 4:02 pmAgain, without knowing the diameter, a reasonable answer can't be forthcoming.I've heard it said that the centrifugal force on the jaws makes them grip with less force, so a workpiece can come loose. Never experienced that myself, but I'll keep it in mind. Sounds "highly theoretical" (unlikely) at my kinda speeds, agreed?
As far as centrifugal force causing a chuck to release, yeah, that's fact. I've experienced that very thing.
I run an 8" three jaw chuck and use soft jaws routinely. With steel jaws, I've had the experience of a part coming loose when running the chuck @ 2,000 rpm. This is far more likely to happen when a thin item is being chucked without excessive pressure. It's not nearly as likely to happen if your soft jaws are made of aluminum.
H
Making soft jaws with no milling machine is going to be a pita. I got a solid-looking vintage milling attachment for my lathe, but it's immobile at the moment due to rust and/or oil (coolant?) turned to varnish, so I see some quality time with degreaser and evaporust in my future before I can even start to learn how to use it. Never had to mill on the lathe before, since my places of employment always had a milling machine or three. Ah, the tribulations of an impecuniated hobbyist retiree. (I know, things are tough all over.)
-Mark
Re: What's the fastest my spindle can go?
I believe you can purchase soft jaws machined to fit the main jaws of your chuck, and you machine the required radius after bolting the jaws in place.
I do not remember where I saw those, but others here will know.
RussN
I do not remember where I saw those, but others here will know.
RussN
- Bill Shields
- Posts: 10459
- Joined: Fri Dec 21, 2007 4:57 am
- Location: 39.367, -75.765
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Re: What's the fastest my spindle can go?
Regarding the chucks at 1500 rpm...
The answer is no...not a problem.
As I mentioned...the problem is primarily found in chucks with hydraulic closers and almost never in that size or speed range with scrolls.
The centripetal load is easy to calculate knowing the size of the jaws and closed position diameter.
Having replacible jaws which hang out from the body of the chuck can contribute to the problem as there is some flex in the body face which can lead to the gripping face of the jaws becoming essentially a cone rather than a cylinder.
Aluminum jaws help because if their reduced mass.
It is a balancing act..
The answer is no...not a problem.
As I mentioned...the problem is primarily found in chucks with hydraulic closers and almost never in that size or speed range with scrolls.
The centripetal load is easy to calculate knowing the size of the jaws and closed position diameter.
Having replacible jaws which hang out from the body of the chuck can contribute to the problem as there is some flex in the body face which can lead to the gripping face of the jaws becoming essentially a cone rather than a cylinder.
Aluminum jaws help because if their reduced mass.
It is a balancing act..
Too many things going on to bother listing them.