PDA

View Full Version : Did I Just Trash My 6-Jaw Chuck?



BigBoy1
06-11-2015, 02:09 PM
I needed to square the end of a large diameter piece of tubing. I placed in my 6-jaw chuck and tightened down and gave the chuck a hand spin to make sure things were OK. (I didn't notice that they were not!) When I turned on the lathe, the centrifugal force threw one of the jaws out of the chuck and when it rotated, the jaw struck the bed and put the crack in my 6-jaw chuck. The chuck only had about half of a revolution under power before the jaw struck so the speed was not high when it hit.

My questions are: Is the chuck safe and usable again? Will accuracy be affect by the crack? I've put the jaw back into the chuck but I had to file down a small burr which was produced when the jaw struck the ways. The jaws seem to work all right.


http://s163.photobucket.com/user/i422twains/library/Tools

TBN
06-11-2015, 02:16 PM
Are you sure it wasn't cracked before this happened?

duckman
06-11-2015, 02:16 PM
Well you can take 3 jaws out and make a 3 jaw chuck, or just chance it.

Daveb
06-11-2015, 02:29 PM
It depends on where the crack is. If it's just a crack in the lip of the T slot, it may be repairable. If it's cracked through the body of the chuck scrap it but first make sure it can't ever be fitted to a machine again. USE A BIG Hammer. No point taking a chance, it could let go without warning and has the potential to kill.
Dave

ranger302
06-11-2015, 02:46 PM
That chuck is now suited for welder positioner duty only. Sorry for your loss.

Yondering
06-11-2015, 02:52 PM
Use the "IMG" code photobucket provides to post your pics, please.

Here you go:
http://i163.photobucket.com/albums/t308/i422twains/Tools/DSCN1176_zpsje9zcc4a.jpg (http://s163.photobucket.com/user/i422twains/media/Tools/DSCN1176_zpsje9zcc4a.jpg.html)

A.K. Boomer
06-11-2015, 02:57 PM
That chuck is now suited for welder positioner duty only. Sorry for your loss.

Im saying what he said...

sorry though - that's some tough luck...

JRouche
06-11-2015, 03:02 PM
Is it steel, cast iron or semi-steel (whatever the heck that is)?? Why cant it be fixed?? TIG welded correctly I dont see a problem.. Fast rotating metal has been welded for many many years without an issue.. JR

Left Handed Spud Wrench
06-11-2015, 03:05 PM
Ah but if a chuck comes apart at work and injures you, you can get a nice settlement from them.

If the chuck blows up at home, you really can't sue yourself. I mean you COULD but that's just daft.

A.K. Boomer
06-11-2015, 03:12 PM
Is it steel, cast iron or semi-steel (whatever the heck that is)?? Why cant it be fixed?? TIG welded correctly I dont see a problem.. Fast rotating metal has been welded for many many years without an issue.. JR

crack is in the tightening screw bed - not to be messed with - never get all the crack out --- up against's loads and vibrations whilst sometimes at high RPM's

Id let an enemy use it - but not a friend lol

Doc Nickel
06-11-2015, 03:48 PM
The body is junk. Absolutely DO NOT USE!

Keep the jaws and/or the scroll, and/or the backing plate, and offer those as parts. I know there's always somebody asking for a set of jaws that might fit some chuck they just picked up or other.

Doc.

Forestgnome
06-11-2015, 03:54 PM
Personally I'd take it apart and braze the crack. I don't see a problem using it after brazing. Cast chucks aren't rated for that high of an rpm in the first place.

Alistair Hosie
06-11-2015, 04:23 PM
Maybe this will be of use to his widow, if he gets a chunk at speed right between the eyes.
In other words this could kill. I too see why some might want to salvage it because of the great loss of the initial expense. I am not experienced enough to say. But those here who are seem to be trying kindly to warn you to accept this loss and move on. Could you not get expert advice and-or buy a new body.I t would be better than a total loss.
Are you perhaps insured? And as said are you sure it was not like that from new,and they told you it was a ventilation slot.I seem to remember seeing it like that when it first came out of the box.
Your Pal (witness AL )

J Tiers
06-11-2015, 04:42 PM
1) It's not safe to use, as much because it may toss a jaw as because it may finish cracking.

2) It may finish cracking at some point unknown, you may not notice, and it may release the part, or come apart (much less likely than releasing the part). I dunno where the released part will go, but it's very likely to be somewhere you don't want it to.

3) with that crack, obviously metal was displaced, there's air where there was metal, so things have moved, the body has been warped or bent, and the chuck isn't going to be accurate anyway.

TOSS THAT S.O.B. BEFORE YOU REGRET NOT DOING IT.

Danl
06-11-2015, 04:52 PM
1) It's not safe to use, as much because it may toss a jaw as because it may finish cracking.

2) It may finish cracking at some point unknown, you may not notice, and it may release the part, or come apart (much less likely than releasing the part). I dunno where the released part will go, but it's very likely to be somewhere you don't want it to.

3) with that crack, obviously metal was displaced, there's air where there was metal, so things have moved, the body has been warped or bent, and the chuck isn't going to be accurate anyway.

TOSS THAT S.O.B. BEFORE YOU REGRET NOT DOING IT.

Yep, Garbage. What a shame.

Dan

Glug
06-11-2015, 05:10 PM
Seems like it'd be fine for use on a rotary table, etc. Or very low speed use as a 4th axis.

And for that type of application, what about drilling and tapping a tangential hole and drawing it together with a fastener?

Daveb
06-11-2015, 05:26 PM
The problem is that as long as the chuck exists it is an accident waiting to happen, even if you only use it on a dividing head or rotary table. At some time in the future, possibly long after you've gone, it could finish up on a rotating machine. You may not care. I have in the past smashed a very expensive chuck because it had a hairline crack through the body, I preferred to accept the loss.
Dave

Richard P Wilson
06-11-2015, 05:34 PM
If I was going to repair it, I'd consider shrinking a steel band around it, between the key hole and the slot. A lot of big steam engines operated like that for many years with shrunk bands round the flywheel hub to counteract cracks from the keyway slot.
Truth be told, though, I think I'd scrap it, 'put it beyond use'. After a traumatic experience like that, I'd doubt the accuracy of it anyway, however well 'repaired'.
Wasn't Boslab looking for a set of jaws for a 6 jaw?

MetalMunger
06-11-2015, 05:55 PM
Make several cuts in the chuck with a cutting torch so that it can never be mounted or used for anything other than a Halibut weight (otherwise we will see a gloat somewhere down the line) then scrap it.

A.K. Boomer
06-11-2015, 06:01 PM
Make several cuts in the chuck with a cutting torch so that it can never be mounted or used for anything other than a Halibut weight (otherwise we will see a gloat somewhere down the line) then scrap it.

Lol spoken from what it would be used as in your neck-O-the woods lol

hope the sockeyes come in this year - last year was a disaster... at least on the Kenai ,

good advice...

Seastar
06-11-2015, 06:08 PM
As someone would say-----
BIN IT!
Bill

janvanruth
06-11-2015, 06:50 PM
i would just weld/braze it and use it
it will have lost some accuracy but wont explode

Doozer
06-11-2015, 06:58 PM
I would use it if the runout is ok.
The area sees little stress in actual clamping.
The crack will not effect the hoop stress from centrifugal
force, because there are 12 freaking bolts holding
the face on the body.
For what it is worth, I am a mechanical engineer.
Bash me if you want, but the crack really does
not look like a problem.
-Doozer

boslab
06-11-2015, 07:11 PM
I have a chuck with a crack, I use it for threading only, low rpm, less than 50, it's ok for that, I don't fancy spinning a cracked chuck at 2000, lots of energy available to remove part of your face, or skull, not worth the risk IMO, I have seen the result of a grinding wheel exploding, ok it was 16" but it killed the guy using it.
Semi steel, at least how I understand it is 3/4 liquid iron and 1/4 low carbon steel scrap, they try to keep the silicon low as it goes exothermic and the cupola foams up like a bad gas weld, aka it's climbing out the top in a steel plant, which meant run btw, you could control it with porous blocks in ladle or converter an bubbling argon through, we called that the anti slop button, high silicon iron is a pig(pun) to handle, if it gets too high it's simply poured on the floor, or plated, smashed up and added at a small amount at a time.
It's a cheap way to make an iron like material for casting into bench vises, chucks lathes etc.
Mark

Wayne Sippola
06-11-2015, 08:12 PM
I agree with Doozer. If it was my chuck, I'd use it. I might weld it or braze it just to feel better, but I don't think that is really required.

spongerich
06-11-2015, 08:26 PM
That thing is just waiting to kill you and your entire family if you even look at it wrong.

Send it to me and I promise I'll melt it down and re-cast it into some safety helmets.

JoeLee
06-11-2015, 08:27 PM
That chuck is now suited for welder positioner duty only. Sorry for your loss.I have to agree!!!

JL.................

JoeLee
06-11-2015, 08:34 PM
I would say that the crack would have to affect how the jaw fits in the T-slot. The T has opened up therefore you have lost the fit. IT may also affect the scroll as there is now a gap along the side of the scroll which will allow fine particles to sift in possible causing it to eventually start to bind.
As mentioned there is the chance that the crack will spread when force is applied.

I have to ask............ what did it do the the bed???? I don't know what type of mount the chuck has but I'm guessing there has to be some damage there also.

JL...............

Mike Amick
06-11-2015, 09:01 PM
How does a hand spun chuck clear everything ... then not ?

oldtiffie
06-11-2015, 09:05 PM
I agree that I would not hesitate to "bin" it - but no surprises there though.

If the job in the chuck was round it would appear that the chuck jaws were at or very close to their outer limit on the scroll plate.

If that is so then perhaps all five - or at least some other - jaws were at or close to that limit as well. If that were the case it would seem that the OP was lucky the job and some of the other jaws didn't "let go" as well.

If that were me that chuck would have been "binned" and on its way to the scrapper as soon as it was removed for inspection.

Bin it now and talk about it later so that no one can talk you into keeping/using and/or "repairing " it.

macona
06-11-2015, 10:12 PM
I dont know, I think it will be fine to use. Its not going to fly to pieces with it being bolted to a solid backplate like it is.

And I think it was cracked before you had this mishap.

DR
06-11-2015, 10:20 PM
What brand of chuck is it?

I see the shallow recess to the right of the affected jaw slot, Buck chucks had those for their product marking. If it is a Buck, it doesn't surprise me it broke. I've had two fairly new 6" Buck Adjust Tru's crack like that.

CalM
06-11-2015, 10:24 PM
No real loss, I've never liked six jaw chucks any way. Too fragile in a wreck! ;-)

Soft jaws for the odd stuff. '=)

oldtiffie
06-11-2015, 10:39 PM
No real loss, I've never liked six jaw chucks any way. Too fragile in a wreck! ;-)

Soft jaws for the odd stuff. '=)

Too true.

If it will fit in a 6-jaw chuck there is a distinct possibility that it will do just as well - or better - in a 3-jaw chuck with correctly pre-machined soft jaws.

ulav8r
06-11-2015, 10:56 PM
Definition of semi steel by the man that came up with it.

A quote from Henry Bessemer

"Before concluding these remarks, I beg to call your attention to an important fact connected with the new process, which affords peculiar facilities for the manufacture of cast steel. At that stage of the process immediately following the boil, the whole of the crude iron has passed into the condition of cast steel of ordinary quality; by the continuation of the process the steel so produced gradually loses its small remaining portion of carbon, and passes successively from hard to soft steel, and from soft steel to steely iron, and eventually to very soft iron; hence, at a certain period of the process, any quality of metal may be obtained. There is one in particular, which, by way of distinction, I call semi-steel, being in hardness about midway between ordinary cast steel and soft malleable iron. This metal possesses the advantage of much greater tensile strength than soft iron. It is also more elastic, and does not readily take a permanent set; while it is much harder, and is not worn or indented so easily as soft iron, at the same time it is not so brittle or hard to work as ordinary cast steel. These qualities render it eminently well adapted to purposes where lightness and strength are specially required, or where there is much wear, as in the case of railway bars, which, from their softness and lamellar texture, soon become destroyed. The cost of semi-steel will be a fraction less than iron, because the loss of metal that takes place by oxidation in the converting vessel is about 2 1/2 per cent. less than it is with iron; but, as it is a little more difficult to roll, its cost per ton may fairly be considered to be the same as iron. But, as its tensile strength is some 30 or 40 per cent. greater than bar iron, it follows that for most purposes a much less weight of metal may be used, so that, taken in that way, the semi-steel will form a much cheaper metal than any with which we are at present acquainted. "

oldtiffie
06-11-2015, 10:56 PM
I needed to square the end of a large diameter piece of tubing. I placed in my 6-jaw chuck and tightened down and gave the chuck a hand spin to make sure things were OK. (I didn't notice that they were not!) When I turned on the lathe, the centrifugal force threw one of the jaws out of the chuck and when it rotated, the jaw struck the bed and put the crack in my 6-jaw chuck. The chuck only had about half of a revolution under power before the jaw struck so the speed was not high when it hit.

My questions are: Is the chuck safe and usable again? Will accuracy be affect by the crack? I've put the jaw back into the chuck but I had to file down a small burr which was produced when the jaw struck the ways. The jaws seem to work all right.


http://s163.photobucket.com/user/i422twains/library/Tools



I have just re-visited this (OP) post/thread and it seems that the work in the chuck - which it seems was not supported or retained in a fixed "steady" was "large".

If the work was a thin-walled tube then it would not be surprising if it flew out of the chuck - it might have been surprising if it had not come out of the chuck.

Forrest Addy
06-11-2015, 11:02 PM
Sorry. It's toast. Demote it to weld positioner, drill press work holder, etc anything that suits out, doesn't require accuracy, or RPM over - say - 200. If it was bigger, it could be a Christmas tree stand.

These things happen and there is no economic remedy regardless of the perceived pity. The casting is cracked so it's safe to conclude it's also distorted and there is no economical repair possible. Scroll damage may not be visible to the eye. The scroll is surprisingly easy to distort. Even if it is heat treated it has some ductility; a big radial shock will do it. The radial pitch has to be accurate as any precision lead screw if the jaws are to track a true circle for all positions.

Bite the bullet. There is no restoring the chuck to its original safety and accuracy. Take a walk around the block kicking a can as you go. These accidents are infuriating but there is no recovery except demotion of the wrecked chuck to some safe lesser service and if the budget will take it rapid replacement.

Some naife may volunteer to "fix" it. Let him try if you think by doing so you can get him to accept that he is not invincible.

mickeyf
06-11-2015, 11:22 PM
a Christmas tree stand. Best Idea yet! Weld some wide stretching legs on it to make it more stable and so that it can never be used as originally intended. You'll both remove any danger and have a one of a kind conversation piece. With a story behind it.

Axkiker
06-11-2015, 11:44 PM
I need a chuck for my dividing head. Ill be glad to take it off your hands for a fee / trade.

Ironwoodsmith
06-11-2015, 11:47 PM
BigBoy1,

If you could elaborate a bit on the accident...was the jaw just barely engaging the scroll? I am attempting to understand the mistake.

1-800miner
06-12-2015, 01:34 AM
Pull the back plate off. Weld the chuck to a weld positioner. Weld the crap out of so the next guy that owns it can't possibly put it back on a lathe.
You can brag on having a very expensive positioner.

It still makes a grown man cry.

tlfamm
06-12-2015, 08:16 AM
BigBoy1,

If you could elaborate a bit on the accident...was the jaw just barely engaging the scroll? I am attempting to understand the mistake.

Yes, please: sorry about the chuck, but help us understand what led to the mishap.

A.K. Boomer
06-12-2015, 08:42 AM
You do have one last attempt cuz you never know,,, contact the manufacturer --- tell them you thought allot of the chuck but had a small accident and could not believe it actually popped the base... ask them if there's anything they can do for you as your in a spot and would appreciate it...

they may have a spare base to send you either for free or low cost...

Like I say you never know,
I had a fair quality kayak paddle and got in a freak situation in the river where for a split second one of the blades got caught between two rocks - I was instantly aware and went to pull it out before it got loaded and it was not under much at all but in that split second it popped and I seen bubbles -- thought "oh fuqe" I can't believe it --- and the blades on these paddles did have a reputation for being brittle...
told the company and totally leveled with them, said it was initially my bad luck and in certain situations would not expect any paddle to hold up to something like that once the current caught up with you and the force was leveraged against it - but that was in no way the case and could not believe how little it took, I did also make a comment on their fiber glass to resin ratio as I felt it way off and way too much resin. showed pics of the blades star cracks from rock impacts,,,

they told me to saw the paddle in half and mail it back ---- a week later I get a brand new one...

worth a shot, sometimes companies will do it just to save face and not have the bad PR, oh yeah I guess I did kinda mention I was pretty popular on a boating site :p

Rosco-P
06-12-2015, 08:44 AM
BigBoy1,

If you could elaborate a bit on the accident...was the jaw just barely engaging the scroll? I am attempting to understand the mistake.

This: When I turned on the lathe, the centrifugal force threw one of the jaws out of the chuck and when it rotated, the jaw struck the bed and ........

How could a jaw be thrown out? Was the chuck already damaged? Bad scroll? Tool large a workpiece for the chuck? Too much jaw overhang? Should the jaws have been reversed to hold the workpiece from the inside and you didn't want to be bothered?

JCHannum
06-12-2015, 08:50 AM
The damaged slot is the number 6 position. That jaw is last in, first out. The jaw was probably out of the scroll due to the oversized workpiece.

A.K. Boomer
06-12-2015, 08:59 AM
Yup - it's his bad all the way, but a company might even give him a break or maybe he can transfer the guts over if he can get just the base at a reasonable price,,,

for the record just because a jaw stays in don't make it right either, they should be staying in by a fair amount not hanging by the edge of the last tooth...

BigBoy1
06-12-2015, 06:09 PM
This: When I turned on the lathe, the centrifugal force threw one of the jaws out of the chuck and when it rotated, the jaw struck the bed and ........

How could a jaw be thrown out? Was the chuck already damaged? Bad scroll? Tool large a workpiece for the chuck? Too much jaw overhang? Should the jaws have been reversed to hold the workpiece from the inside and you didn't want to be bothered?

The chuck was NOT damaged before I started. Yes, the piece of tubing's diameter was just at the maximum limit of the chuck's capability. I had it chucked and was concerned about the diameters being so close to the maximum that is why I hand spun the chuck to check of things were OK. If a jaw was not "caught" it would let me know with the hand spin. However there must have been sufficient friction to hold the jaw in place with a hand spin but the centrifugal force generated by the motor was sufficient to over come the friction and sling the jaw outward. It was the number 6 jaw and the scroll may have engaged the jaw by just a tad or had not engaged it at all. I'll never know.

I examined the lathe ways and could find no damage to them. The jaw had moved outward sufficiently far so the strike point on the lathe ways would have been on the very most out edge of the ways, not on the ground surfaces.

The maker of the chuck is Buck. I had to make the back plate to fit my lathe as it has a threaded spindle.

A.K. Boomer
06-12-2015, 08:34 PM
The damaged slot is the number 6 position. That jaw is last in, first out. The jaw was probably out of the scroll due to the oversized workpiece.

BB listen to JC --- it will at the very least help you to avoid future crashes like this,

this sucks for sure - but can't help but say it's all your fault, that has to be accepted --- simply spinning a chuck to check for proper jaw engagement just don't cut it...

fact is - is when you know your even anywhere close to pushing the boundaries what has to happen is last jaw inspection - and like JC stated - that would mean #6,,,

you tighten up the workpiece - then first tug on #6 to see if you even need to inspect any further or totally abandon the idea, if it holds - next step would be to start backing off the scroll to see how much it takes for 6 to "pop" --- next step is to tighten it all up without 6 and see how much lead scroll in engaged, if still not enough for comfort maybe toss around leaving it out completely and also remove 4 and 2 and using it as a three jaw if it's a light load situation...

and if that's the case don't forget to go through the same practice for #3...

Lots of judgement calls that come from experience - but don't be dismayed -- You just got some... and it's not something you read in a stupid book - far more important - something called "hands on" that you won't soon forget...

look at it this way - in this particular category I would not have considered you in any way shape or form "wise"

but if your paying attention you are now... also - all logic aside while in the comfy armchair mode --- everybody makes mistakes... Yes by all means beat yourself up a little - can't stand the attitude of "just move on"

self ridicule is the catalyst for change --- just don't go into a fetal tuck everytime it gets windy outside... :p

mike4
06-12-2015, 08:44 PM
I will mount a large piece of tubing with the jaws inside if the diameter is close to the maximum for the chuck, that is a way to help prevent this sort of gut wrenching mishap.

That way the jaws are inside of the chuck base far enough to have quite some material holding them in place .

If the supplier does not offer replacement parts , like others have said use it for a rotary table or welding positioner chuck , but braze a backplate onto it just to help prevent use on a lathe .
Michael

PStechPaul
06-12-2015, 10:50 PM
Seems to be about evenly divided opinion about whether the chuck can be repaired and used safely. I tend to agree with those that say it would be OK because it is bolted to the back plate, and there is really not that much centrifugal force at most speeds to be dangerous. Grinding wheels run at about 3500 RPM and the energy is proportional to the square of the velocity, and their construction makes them prone to sudden fracturing and slinging chunks at high speed. At 1000 RPM or less it has 1/10 the energy. There is probably more danger from a part becoming loose or a tool bit breaking.

A.K. Boomer
06-12-2015, 11:00 PM
You forgot the mass of the chuck itself --- where if just cut in half and dropped on your forehead from just a three or four feet high might kill you...

LKeithR
06-12-2015, 11:03 PM
That chuck is now suited for welder positioner duty only...

Not a good idea--someone else may see the chuck at a later date and decide to throw it on a lathe...then what?


...Why cant it be fixed?? TIG welded correctly I dont see a problem...

Then you need to get your glasses changed--once broken like that a chuck should never be repaired or used again...


Personally I'd take it apart and braze the crack. I don't see a problem using it after brazing...

NO! NO! NO! NO! NO! NO! NO!


Seems like it'd be fine for use on a rotary table, etc...

See above--you don't want to leave a ticking time bomb for someone else to find...


The problem is that as long as the chuck exists it is an accident waiting to happen, even if you only use it on a dividing head or rotary table. At some time in the future, possibly long after you've gone, it could finish up on a rotating machine...

YES..........IT'S REALLY THAT SIMPLE FOLKS...


If I was going to repair it, I'd consider shrinking a steel band around it, between the key hole and the slot...

Nope...


i would just weld/braze it and use it
it will have lost some accuracy but wont explode

Are you out of your mind?


...Bin it now and talk about it later so that no one can talk you into keeping/using and/or "repairing " it...

YES!

I really thought people one here would know better. A chuck that is cracked like that is a ticking time bomb--no other way to put it. It should be taken out of service and rendered unusable immediately!

It's one thing to do something dumb in the privacy of your own shop but to come on a forum like this--where a lot of people are just learning how to do things right--and tell someone that it's OK to something which is potentially life-threatening, is just plain stupid and irresponsible. Sorry to be so harsh but there's really no other way to put it...

oldtiffie
06-13-2015, 01:17 AM
There are a wide variety of opinions and options here as to what to do with that chuck (or by inference any similar tool etc. that you may have bought or are considering buying).

First of all as for me I would never buy it or similar without at least trying it with a comprehensive crack test and even then it depends on your judgement of the crack test result.

https://www.google.com.au/?gws_rd=ssl#q=crack+testing

https://www.google.com.au/search?q=crack+testing&biw=1536&bih=710&tbm=isch&tbo=u&source=univ&sa=X&ved=0CGQQsARqFQoTCLu7p4T1i8YCFYJ8vAod8EMAkg

Blogwitch
06-13-2015, 03:36 AM
It wasn't too long ago that a very skilled motorcycle engineer and machinist from my area had a part come off a faceplate that hit him square in the chest, he was dead before he hit the floor.

He never expected to die that day, but what you are trying to hang onto could easily give the same result.

What does it take to persuade someone that there are some things you shouldn't even think about, never mind try?

Just smash it up and get rid, or you could just be another statistic with a sad story.


John

Rosco-P
06-13-2015, 06:28 AM
The chuck was NOT damaged before I started. Yes, the piece of tubing's diameter was just at the maximum limit of the chuck's capability. I had it chucked and was concerned about the diameters being so close to the maximum that is why I hand spun the chuck to check of things were OK. If a jaw was not "caught" it would let me know with the hand spin. However there must have been sufficient friction to hold the jaw in place with a hand spin but the centrifugal force generated by the motor was sufficient to over come the friction and sling the jaw outward. It was the number 6 jaw and the scroll may have engaged the jaw by just a tad or had not engaged it at all. I'll never know.

I examined the lathe ways and could find no damage to them. The jaw had moved outward sufficiently far so the strike point on the lathe ways would have been on the very most out edge of the ways, not on the ground surfaces.

The maker of the chuck is Buck. I had to make the back plate to fit my lathe as it has a threaded spindle.

You wound the jaws all the way out to grip a part externally when you should have removed and flipped them to hold it internally. You took your chances and paid the price. Next time you could be more then just "ROAD KILL on the Information Super Highway".

Black_Moons
06-13-2015, 09:00 AM
That chuck is now suited for welder positioner duty only. Sorry for your loss.

Agreed. Get your stamps out and mark that chuck '10 RPM MAX' on the face in huge print.

Ideally weld the **** out of that chuck onto a large bar for your welding positioner so its really imposable to get it back onto a lathe properly.

cameron
06-13-2015, 09:33 AM
For what it is worth, I am a mechanical engineer.
Doozer

I don't think it's worth a lot.

If I ever use that line again in a "discussion" with my wife, they'll probably be
my last words.

Forestgnome
06-13-2015, 10:14 AM
What a bunch of voodoo! You'll get a similar chorus if you ask about rebuilding your own welding or scuba regulators. Bad magic! So nobody here repairs or builds anything that spins over 200 rpm? Nobody here buys and uses a Chinese chuck or boring head without first sending it to a lab for non-destructive testing? I think one of the tenets of lathe safety is being missed here. The plane of the rotating chuck is essentially a "no stand zone". Same thing with a loaded faceplate. If nothing else it prevents oil racing stripe.

JCHannum
06-13-2015, 11:05 AM
The failure mode might not be a piece of the chuck flying off, but a heavy workpiece being launched across the shop. The chuck is damaged and should not be used or attempts be made at amateur repair methods.

Brazing or TIG welding of cast or semi-steel is not something to attempt casually. Probably the best suggestion is to shrink a steel band on the chuck. But even if a sound repair is accomplished, the chuck's accuracy and holding power have been compromised. Junk it and chalk it up to experience.

LKeithR
06-13-2015, 12:51 PM
What a bunch of voodoo! You'll get a similar chorus if you ask about rebuilding your own welding or scuba regulators. Bad magic! So nobody here repairs or builds anything that spins over 200 rpm? Nobody here buys and uses a Chinese chuck or boring head without first sending it to a lab for non-destructive testing? I think one of the tenets of lathe safety is being missed here. The plane of the rotating chuck is essentially a "no stand zone". Same thing with a loaded faceplate. If nothing else it prevents oil racing stripe.

OK, I give up. Seriously folks, there are people here who are trying to get you killed or injured..........caution, Darwin at work...

Doc Nickel
06-13-2015, 02:25 PM
So nobody here repairs or builds anything that spins over 200 rpm?

-Of course we do. But we also use clean, usually new, uncracked metal.


Nobody here buys and uses a Chinese chuck or boring head without first sending it to a lab for non-destructive testing?

-Non sequitur. A new part is assumed to be, you know, new, which is also assumed to be, you know, not cracked.

Why is this even a question? The OP's chuck has major structural damage that you can see from across the room. This is not an issue of a cheap new chuck being slightly out of balance or something- it has a major, obvious structural flaw.


I think one of the tenets of lathe safety is being missed here.

-It certainly is. Don't Put A Heavily Damaged Chuck Back On The Lathe. With something like a lathe chuck, there is no such thing as a "small" crack- any crack is a serious structural flaw that can lead to failure in use. Centripetal forces at even relatively low speeds are significant, and a separation can lead to a large piece of metal flying across the room.


The plane of the rotating chuck is essentially a "no stand zone".

-That's no safety. What if the piece of chuck goes straight up, bounces off a ceiling beam or truss and falls on your head? What if your wife or a friend just stopped by and was walking past that "no stand zone"? If/when the chuck fails, it'll be heavily out of balance- if the lathe isn't solidly bolted to the floor, the forces could easily rock the lathe enough to tip it over- and quickly enough you're still in the "what the hell just happened" stage after the chuck exploded six inches from your face, and so crushes you before you can run or dodge.

These are not forces to be trifled with. We all get a little lax when everything runs smoothly- because everything on our lathes is relatively well balanced. But there's still massive forces at work- we harp on people about just leaving the chuck key in! Why? Because if it's in and you start the lathe, that key is going to be flung across the room, possibly hit or even kill someone, or at the very least, strike some part of the lathe and damage the saddle or ways or whatever.

And now you say it's okay to go a head and run a badly cracked chuck because if it lets go, it's okay simply because you (probably) won't be standing in front of it? When the chuck lets go, it'll be turning far faster than the chuck key would have been when it leaves the machine. Meaning far, far more energy, and it'll likely be a bigger, heavier chunk of steel too- actually several of them, as each jaw will likely become a separate missile.

But that's okay because you'll be standing to the side? That's lunacy.

Doc.

Axkiker
06-13-2015, 04:14 PM
I think what would scare me the most wouldnt be the chuck itself coming apart but letting the part being made fly out.

Doozer
06-13-2015, 04:17 PM
I love how most everyone parrots, "If it is cracked, it must be junk",
without actually analyzing the situation. Sheep.
There are 12 bolts holding the face, to the body and the back plate.
The crack means nothing to the hoop strength of the face.
Have any of the sayers of nay even taken a 6 jaw Buck apart?
I certainly have, and a crack right where it is, doesn't mean spit.
Do what you want with the chuck, but it is better to listen to reason
than hysteria.
-Doozer

janvanruth
06-13-2015, 04:56 PM
I wonder how oddly sized parts can ever be secured to a face plate?
Mostly by just a couple of bolts i believe.
Admittedly high grade and plenty of them.
But attached to a rather flimsy, in comparison to a backplate, faceplate.
Probably not exactly balanced either.

Now there is a round, still fairly well balanced, be it partly cracked and brazed/welded, chuck.
Attached to a not so flimsy, in comparison to the faceplate, backplate.
By plenty high grade bolts.


Which one is the most dangerous?

CarlByrns
06-13-2015, 04:58 PM
-Non sequitur. A new part is assumed to be, you know, new, which is also assumed to be, you know, not cracked.


That's not a good assumption. I've bought brandy-new grinding wheels with cracks (ring test) and have seen brand-new factory direct parts with holes chamfered on the wrong side.

I used to work for Ford and we used to get brand new cars off the transporter that said 'Ford' on one side and 'Mercury' on the other side. Quality is Job 1 :)

Mcostello
06-13-2015, 10:14 PM
How far away are You from Central Ohio? Let Me know when to duck! :)

The Artful Bodger
06-13-2015, 10:29 PM
I would say to repair the crack as best it can be done, weld, braze or whatever, then stamp or engrave in clear letters on the face of the chuck "Not safe for lathe use".

JoeLee
06-13-2015, 10:40 PM
Make a lamp out of it and move on.

JL..................

A.K. Boomer
06-13-2015, 10:44 PM
Would make an awesome ceiling fan motor drive fan mount drive thingy,,, nah little heavy - probably not... forget it...

oldtiffie
06-13-2015, 10:46 PM
I rarely buy "used"/"pre-loved/"second-hand stuff (my shaper was an exception as it was in exceptional condition) as I am a lot safer with the manufacturer's "name" and warranty available. Most used stuff is sold on an "as is - where is" basis with no warranty credible provided.

I have two 6-jaw chucks but they are an integral part of my drill-sharpening machines:

http://images.machineryhouse.com.au/products/G198/700/13_Drill-Grinding-Attachment.jpg

I find that the normal 3- and 4-jawed chucks suit my needs pretty well as does using soft jaws on a 3-jawed chuck.

If I were to but a 6-jaw chuck it would be one from this selection by "Bison".

http://www.bison-bial.com/lathe-chucks/3865-160

A.K. Boomer
06-13-2015, 11:21 PM
I rarely buy "used"/"pre-loved/"second-hand stuff

Pre-luved? why'd ya have to go and make it all dirty and stuff...

I got a brand new Mill and it's still a hoe - (but a tight one) lol

the beauty of getting something used is allot of times it's better quality and cheaper too boot - (not that kinda cheap - git that mind of yours out of the gutter) :p

Doc Nickel
06-13-2015, 11:24 PM
I love how most everyone parrots, "If it is cracked, it must be junk",
without actually analyzing the situation. Sheep.

-Personally, I love how anyone who follows conventional wisdom is referred to as a "sheep".

Everyone here reflexively yells at anyone who leaves a key in the chuck, because if the chuck is started, it can and will fly out and cause damage or injury or even death. I've seen people on this board mention that about a photo in Craigslist, in reference to an old lathe that clearly doesn't even have a motor.

But here we have a badly cracked chuck- a part that spins in use, and at speeds of anywhere from a few hundred to a few thousand RPM- and people saying it's okay because a few bolts will hold it together. Or if it DOES explode, it's okay because you're not supposed to be standing in front of it anyway.

Doc.

Doc Nickel
06-13-2015, 11:25 PM
I've bought brandy-new grinding wheels with cracks (ring test)[...]

-Why not just put a few bolts through it? According to some people here, that should fix it up just fine. :D

Doc.

CalM
06-13-2015, 11:38 PM
I might fix a nice chuck like that by properly preparing the joint and furnace brazing. It's an amazingly secure joining method when simple cleanliness is adhered to.

But even if the crack were made whole again, I would always consider the chuck second class and only suited to rough work.

What kind of 6 jaw would that be? We want our tools to give us both service and pleasure.

Describe the damage and put the thing on ebay. Buyer be ware! ;-)

ulav8r
06-13-2015, 11:50 PM
The crack is open. It was caused by the jaw hitting the bed. This means the jaw mortise has spread, probably more on the outer end. Even if the crack is repaired, the jaw mortise is still distorted, so you will have a 5 jaw chuck.

A.K. Boomer
06-13-2015, 11:55 PM
Im with ya Doc - as much as I like the Dooze and his shoot from the hip attitude im all for benching that sucka

Question, is the backing plate what everyone is talking about in having no fear cuz it will hold it all together anyways?

If that's the case that's insane, im a mechanical engineer too, actually decades of it...

the crack is actually on the side of high load --- you know - where the jaws are hanging out creating leverage on it whilst holding the material?

so - now there's clearance -- yet when you tighten the chuck it will seek a mechanical equilibrium -- forcing the crack further apart whilst facing and turning,,, even if you don't get killed --- flipping your work is going to produce crap, uhhh unless you mark it and then use a torque wrench to tighten up your key and create the prefect deviation that you did before with your flexible crap chuck... nice ehh?




so once it spreads and the base part starts to go at something like over 2,000 rpms are you telling me the little bolts that are holding it to the drive plate in the back are supposed to make it all fine and dandy? first off - say "bubbye" to the work piece and hope it does not kill you - but then again if it don't you might wish it did when the jagged piece of chuck clocks you in the forehead,,, welp --- all's I got to say is we went to different engineering schools...
yeah - guess im glad mine was self learned...

here's what the facts are that are actually staring at you in the face,,, the jaw took a shot and cracked the first line of defense of what makes a chuck a chuck and do what it does - BE RIDGED --- and the further in you go the weaker things get for trying to hold the jaw side --- it's actually called "leverage" that's how stuff works ...


I don't have to ever take the chuck apart to tell you all that I know about it --- all I have to do is see where it cracked...

J Tiers
06-13-2015, 11:56 PM
I love how most everyone parrots, "If it is cracked, it must be junk",
without actually analyzing the situation. Sheep.
There are 12 bolts holding the face, to the body and the back plate.
The crack means nothing to the hoop strength of the face.
Have any of the sayers of nay even taken a 6 jaw Buck apart?
I certainly have, and a crack right where it is, doesn't mean spit.
Do what you want with the chuck, but it is better to listen to reason
than hysteria.
-Doozer

Buncha BS...

It's junk because it is BENT OUTTA SHAPE. IT USED TO BE ROUND, like a nice new chuck, and now, it ain't. It won't hold parts as accurately, or as securely as it did.

I don't expect it to explode, although I'd not spin it at it's limit rpm anymore, it is visibly defective, and you'd have to be a blinking idiot to do that.

I DO think it may fail to hold right, might easily let a part move and possibly even let a part slip right out, in a worst case. Since I don't like worst cases like that, I'd prefer to just not DO that.

As for "not meaning spit", apparently you think a crack and visible material distortion will make it more accurate, make it hold the jaws straighter so they are more securely located for best operation. If so, I'm happy for you, off in your little world of rainbows and butterflies.

oldtiffie
06-14-2015, 12:14 AM
Originally Posted by oldtiffie

I rarely buy "used"/"pre-loved/"second-hand stuff






Pre-luved?

why'd ya have to go and make it all dirty and stuff...

I got a brand new Mill and it's still a hoe - (but a tight one) lol

the beauty of getting something used is allot of times it's better quality and cheaper too boot - (not that kinda cheap - git that mind of yours out of the gutter) :p



Buying something "used" etc.. is some where between - or both - a "pig in a poke" and a school money-raising "lucky dip"

https://en.wikipedia.org/wiki/Pig_in_a_poke

https://www.google.com.au/?gws_rd=ssl#q=pig+in+a+poke

https://www.google.com.au/search?q=lucky+dip&biw=1536&bih=710&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBwQsARqFQoTCIa6xrGojsYCFYNAvAodMOIARQ

https://www.google.com.au/?gws_rd=ssl#q=lucky+dip

If I can't find a really good "new" one I'd either "give it a miss" or wait until I had the money.

The Artful Bodger
06-14-2015, 01:42 AM
Oh no no chaps! On this forum, and others like it, you should not buy new but must buy old iron!:confused:

Spandau
06-14-2015, 02:28 AM
I'm never turning on my lathe again. It might put my eye out.

Boostinjdm
06-14-2015, 03:02 AM
I wouldn't call it junk, but I'd never be comfortable using it on a lathe again.

It could be cross drilled and bolted. Then used on a rotary table, weld positioner, or used for bench work holding stuff for assembly/disassembly, etc.

JoeLee
06-14-2015, 09:32 AM
What brand of chuck is it?

I see the shallow recess to the right of the affected jaw slot, Buck chucks had those for their product marking. If it is a Buck, it doesn't surprise me it broke. I've had two fairly new 6" Buck Adjust Tru's crack like that.What caused you's to crack??

JL.............

JoeLee
06-14-2015, 09:35 AM
If you insist on using the chuck you should invest in one of these.

JL................

http://www.tudorplace.com.ar/images/HenryVIIIarmor03.jpg

Richard P Wilson
06-14-2015, 09:52 AM
OK, 9 pages in, can I summarise? Its scrap, it would be a risk to use it, even if repaired, and anyway, its accuracy has got to be questionable. Best thing is 'put it beyond use', so nobody now or in the future tries to use it, so salvage the backplate, put the chuck out of its misery, lay it on the floor, hit it hard on the opposite side with a 14 lb hammer. The job the OP started by cracking it on one side is now complete.

PixMan
06-14-2015, 09:56 AM
Clearly there will never ever be a complete agreement on what to do or not do with the chuck. Therefore I will only say I hope you (the OP) is safe no matter what you choose to do. No one else can assess and accept a level of risk for you.

I liken it to my motorcycle riding. I enjoy it, and take a lot of precautions by always riding in full protective gear, even on the hottest days. Others choose to completely stay away from motorcycles, ride with just a helmet, maybe a helmet, jacket and gloves, while others with ride with no helmet in shorts, a T-shirt and sneakers. We all accept a certain level of risk which we deem safe for us. However, not everyone in the sport considers the feelings of the family who would lose you if you had an incident.

There simply is no clear "line in the sand" for everyone.

Be safe, have fun, live with few regrets.

A.K. Boomer
06-14-2015, 04:45 PM
Note to BigBoy ---- also took a big set of nads to post your crash on here and you can feel good about this ----- you probably are going to save someone else the trouble as they may now remember to double check a few things...

most all kept it together here and while may have stated was your fault were still respectful cuz after all - we all do it in one form or another...

so in that respect kudos to you and may you have decades of crash free existence... :)

BigBoy1
06-14-2015, 07:00 PM
My intention was not to create "fire storm" of controversy but to ask a simple question, to which I have received many excellent replies.

Yes, I'll be the very first one to admit that is was an excellent "learning experience" for me. As I have heard many times, "Mistakes create experience" so now I have gained some experience!

The cracked chuck will probably become a boat anchor. I did send an email to Buck asking if chuck bodies could be purchased separately but haven't received a reply yet. I think I'll look around to see if I can find a used 6-jaw chuck as I find I use it a lot more that I thought I would. (I make wind chimes and the 6-jaw is great for holding the tubing.)

Thanks again for all of the very helpful and useful comments.

MetalMunger
06-14-2015, 10:08 PM
The cracked chuck will probably become a boat anchor.
A little light for a boat anchor but just about right for a 300lb. halibut.

http://i.imgur.com/BtHVlX7.png?1

Glug
06-15-2015, 02:55 PM
So how many rpm until it would blow? Does anyone have access to a test rig?

We could have a pool of predictions.

Richard P Wilson
06-15-2015, 03:12 PM
So how many rpm until it would blow? Does anyone have access to a test rig?

We could have a pool of predictions.
Certainly, Anyone with a lathe capable of 2000rpm on a variable speed drive has a test rig. Just put it on, stand to one end and dial up the speed till she blows. Wearing a motorcycle helmet and having a spare pair of trousers handy are advisable for this. Are you volunteering?

Black_Moons
06-15-2015, 04:05 PM
My intention was not to create "fire storm" of controversy but to ask a simple question, to which I have received many excellent replies.

Yes, I'll be the very first one to admit that is was an excellent "learning experience" for me. As I have heard many times, "Mistakes create experience" so now I have gained some experience!

The cracked chuck will probably become a boat anchor. I did send an email to Buck asking if chuck bodies could be purchased separately but haven't received a reply yet. I think I'll look around to see if I can find a used 6-jaw chuck as I find I use it a lot more that I thought I would. (I make wind chimes and the 6-jaw is great for holding the tubing.)

Thanks again for all of the very helpful and useful comments.

I wouldn't boat anchor it just yet, Personally I really like the idea of welding/painting positioner, or bench vise/etc. Its very hard to securely grip thin walled round objects on the bench! Especially if you need to say, unscrew some cap/bolt on a motorcycle shock. Any job that spins veryyy slowly and the only danger will be a 50lb chunk of chuck dropping off and landing on your foot. (Ok, could be nasty but you'll survive after the bones heal)

Seriously, get some stamps (or a dremel engraving tool, etc) and put
CRACKED BODY
60 RPM MAX
or some other stupidly low number in large print in several places on the body.

PStechPaul
06-15-2015, 05:57 PM
Here's what can happen under extreme conditions:


https://www.youtube.com/watch?v=Z9hwXQFrRe4

Or:

https://www.youtube.com/watch?v=vYNTC9v7zWk

I found an on-line calculator to determine the centripetal force on a 6" diameter 40 pound chuck at 2000 RPM:

http://www.calctool.org/CALC/phys/newtonian/centrifugal

It comes to over 13,000 pounds of force. However, I think this is distributed across the circumference of the flywheel (chuck), so if the chuck is 3" thick and the circumference is 18", then the iron is subjected to a force of 13,000/54 = 240 PSI. I'm neither a mechanical engineer nor a physicist, but I understand the basic concepts, and I still feel that the chuck is in no great danger of exploding. But there will most likely be a problem exerting sufficient work-holding force unless the crack is adequately repaired.

Any piece of cast iron or perhaps even semi-steel may have internal cracks which might not be seen on the surface, yet may be sources of failure. Unless the chuck has been X-rayed, and has never been subject to any abuse, you don't know what you may have, especially if purchased used, or from foreign sources. I wonder if a "ring test" may be employed to test the integrity of a chuck?

mike4
06-15-2015, 07:20 PM
That video just shows how braindead those fools are.
It would be instant shut down of the vehicle and all of the participants would be looking for a new job just as quickly if it was to happen in my shop.
Abuse of equipment is never tolerated or condoned in any way.
If one of these morons was to get hurt by these actions there is NO way that I would pay or wear any liability for injury caused by stupidity.

Michael

flylo
06-15-2015, 08:19 PM
What brand lathe was that? I agree with Mike4, that was just plain stupid & in the middle of it all one of the brighter ones want's to know if they have a fire ext. Stupid is as stupid does.

A.K. Boomer
06-15-2015, 08:52 PM
geeze what a bunch of dumbasses - you gotta watch those rpms on them old rotary's - they can get away from you,,,

terrible filming,,,

but the brake rotor malfunction takes it too a whole new level --- they can't even "play" dumb on that one... there removed all doubt...

BigBoy1
06-17-2015, 07:24 AM
Well I bit the bullet and I used the Enco 20% off and free shipping deals and have ordered a new Buck 6-jaw chuck. Probably one of the first "new" items other than cutting tools I have bought for my lathe!

The old 6-jaw has currently been relegated to being a door stop.

PixMan
06-17-2015, 08:45 AM
Good for you, good move. You will sleep better, your grass will be greener and all is good in the world.

Seriously, you got a great bargain and the pain of the spend will be gone the first time you use it.

A.K. Boomer
06-17-2015, 09:28 AM
That's the thing - once accepted it becomes just a mere little hiccup with an important lesson attached to it,,,

where as used as is could be a life long game changer of total regret - if you even make it that far...

technically - we don't even know where that crack stopped, just because we can't see it elsewhere does not mean it does not exist,,, so yes good move...

BigBoy1
06-17-2015, 10:24 AM
Before making it the door stop, just out of curiosity, I measured the diameter of the chuck next to each of the jaws. Guess what? The chuck is no longer round! There was about 0.050" of a difference in diameters between the largest and smallest diameters. Since it was no longer round, that convinced me to make it the door stop.

The Artful Bodger
06-17-2015, 03:39 PM
Now get a chunk of steel and weld it across the crack. You will still be able to use it as a stationary holding device but no one will ever mount it on a lathe.

oldtiffie
06-17-2015, 10:14 PM
I admit that it seems to be being "wise after the event" (20-20 hind-sight?) but I'd have thought that someone here - me included - would have measured the OD of the chuck as the OP has now done as soon as the crack was seem.

But we've all learned something about risks - and that is no bad thing at all.

But on the other hand I get a big chill down my back as soon as someone (who should know better - not the OP) gets all "gung ho" which may be seen to be as you'd expect from a "Shade tree mechanic" or a "red neck".

https://www.google.com.au/search?q=google&rls=com.microsoft:en-AU:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7IRFC_enAU360&gfe_rd=cr&ei=YSeCVef-IqHu8wfp8oiYBQ&gws_rd=ssl#q=gung+ho

https://www.google.com.au/search?q=google&rls=com.microsoft:en-AU:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7IRFC_enAU360&gfe_rd=cr&ei=YSeCVef-IqHu8wfp8oiYBQ&gws_rd=ssl#q=redneck

https://www.google.com.au/search?q=google&rls=com.microsoft:en-AU:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7IRFC_enAU360&gfe_rd=cr&ei=YSeCVef-IqHu8wfp8oiYBQ&gws_rd=ssl#q=shade+tree+mechanic

https://www.google.com.au/search?q=shade+tree+mechanic&rls=com.microsoft:en-AU:IE-SearchBox&rlz=1I7IRFC_enAU360&biw=1536&bih=710&tbm=isch&tbo=u&source=univ&sa=X&ei=hCqCVa3SLaPYmAW_hIGwBQ&sqi=2&ved=0CC8QsAQ

Yeah - we are not short of any of these people here in OZ either.

Me too?

Could be!!!

Doozer
06-17-2015, 10:39 PM
I have a 6" Buck 6-Jaw.
Do you want to sell me your jaws?
Mine only has the outside jaws.
Would like a set of inside jaws as well.
Let me know.
-Doozer

CalM
06-17-2015, 11:00 PM
That video just shows how braindead those fools are.
It would be instant shut down of the vehicle and all of the participants would be looking for a new job just as quickly if it was to happen in my shop.
Abuse of equipment is never tolerated or condoned in any way.
If one of these morons was to get hurt by these actions there is NO way that I would pay or wear any liability for injury caused by stupidity.

Michael

I've always wondered just how much energy (heat) you could put in to a disc brake. From what is seen in that video, A LOT!.

I might have had the fire suppression equipment at hand, and NOT had the tire on the ground beneath.

But Boy! That was a fun watch!


I would do that in a hearbeat , out doors, best at an established junk yard that takes burn outs ;-)

J Tiers
06-18-2015, 12:01 AM
Before making it the door stop, just out of curiosity, I measured the diameter of the chuck next to each of the jaws. Guess what? The chuck is no longer round! There was about 0.050" of a difference in diameters between the largest and smallest diameters. Since it was no longer round, that convinced me to make it the door stop.

Gee..... A couple of us said that, back in the middle of all the "weld it up and use it" noise.... Of course nobody noticed what we said....

2ManyHobbies
06-18-2015, 01:08 AM
I found an on-line calculator to determine the centripetal force on a 6" diameter 40 pound chuck at 2000 RPM:

http://www.calctool.org/CALC/phys/newtonian/centrifugal

It comes to over 13,000 pounds of force. However, I think this is distributed across the circumference of the flywheel (chuck), so if the chuck is 3" thick and the circumference is 18", then the iron is subjected to a force of 13,000/54 = 240 PSI. I'm neither a mechanical engineer nor a physicist, but I understand the basic concepts, and I still feel that the chuck is in no great danger of exploding. But there will most likely be a problem exerting sufficient work-holding force unless the crack is adequately repaired.My concern wouldn't be if one could chuck it up and spin it at a given speed without it flying apart. The problem is going to be forces exerted on that chuck if it was ever again used for cutting. It's a larger more catastrophic version of chucking up a 1/2" endmill in a Jacob's chuck and hogging away as if it were an endmill mounted in a taper or collet holder. What is going to happen is that at some point a cutting force is going to cause more flex than is expected or desired and the work is going to climb up and over a tool by some modest integer of expected cutting depth. The best case is it quickly knocks the tip off the cutting tool or musses up the surface finish. Anything that involves the work becoming an off-axis rotary hammer, being torqued over at an angle and impacting less movable objects, or just fracturing a chunk out of that chuck at high speeds is going to ruin a day even if one is lucky enough to only need to change the shorts afterwards.

In addition to the math above not considering cutting forces, it doesn't account for the energy in something like a chuck jaw that has to clear the slot before it can let go. In that case, it isn't going in a 6" circle at 2000 RPM (or ~3100 ft/min) but closer to a 9" circle at 2000 RPM which is closer to 4700 ft/min but 2.25 times more energy. I'm not entirely sure what the weight of a single jaw may be, but extrapolating up from a 4" 3-jaw one in the garage, I'm coming up with numbers that approximate the energy of small handgun rounds.

steve herman
06-18-2015, 03:05 AM
I passed over this discussion several times but read the whole thing tonight and learned a lot. I side with those that called for junking the chuck and sighed a sigh of relief when the OP decided to get a new chuck. (maybe check it for cracks just for the heck of it).
Iím 80 years old and still have 10 fingers, 10 toes and two eyes not because Iím super careful, Iíve done a lot of dumb things, I think I just beat the odds. But why take the chance?
The advice here is great and I check in every day.
Steve

Daveb
08-29-2015, 06:09 PM
If you insist on using the chuck you should invest in one of these.

JL................

http://www.tudorplace.com.ar/images/HenryVIIIarmor03.jpg


There's one of these in the Tower of London with a huge hole in the breastplate, might have been a cannonball, might have be a chuck with a crack in it.
Dave

Rosco-P
08-29-2015, 07:40 PM
There's one of these in the Tower of London with a huge hole in the breastplate, might have been a cannonball, might have be a chuck with a crack in it.
Dave

Did it say who the last owner/wearer was? Anyone we know?

oldtiffie
08-29-2015, 10:02 PM
These?

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTCJjszc2JMxorUVmCjpl-pf7q7fuvJl9WQUp2IaCcnUJNPjpKyJg

http://i831.photobucket.com/albums/zz238/estcrh/tameshi%20gusoku/100_7191.jpg

Daveb
08-30-2015, 06:10 AM
Not those, looks like the guy suffered the death of a thousand dents.
I last saw the breastplate in the Tower about 50 years ago, it had a hole about 4" diameter clean through it, not a lot of distortion to the breastplate except around the hole. Don't know who was wearing it, I think they found it in the moat. Next time I go, I'll ask if there were any chuck parts found with it.
Dave

philbur
08-30-2015, 08:26 AM
Do what you want with the chuck, but it is better to listen to reason
than hysteria.
-Doozer

The trick is knowing which is which!

Phil:)