What's going here?

[mikey]

I don't understand the mechanics of what Joe is doing.

Nobody has addressed your question yet so I'll try. What Joe is doing is relying on the ability of a chuck to run accurately for a first operation turning. A first operation is when you initially turn/drill/bore a work piece the first time. As long as you don't remove the work piece from the chuck the work produced will be concentric with the spindle even if the chuck has excessive run out. What Joe did was to make a collet of sorts in a first operation process. You will note that he takes great care NOT TO MOVE the work piece after he reams it. This allows the bore to remain true to the lathe centerline and anything you clamp in that collet will also run true provided it has an accurate outer surface like the drill rod he used. If he had moved the collet then run out would have increased, probably by a lot. Pretty cool trick if you ask me.

A second operation is when you must turn/bore/drill/ream a work piece that has already been operated on. In that instance, the accuracy of the chuck or holding device is paramount because you cannot trick your way into accuracy like this. Second op work generally requires a collet system of some kind if tolerances allow, or a 4 jaw chuck if you must have zero run out.

So, for a first operation turning you can use just about anything that will hold the work solidly, even if it has more run out than is ideal. As long as you don't remove it from the chuck the resulting work you do will remain concentric with the spindle centerline. Once you remove it or if you work on another piece that has already been turned or otherwise operated on then you need an accurate work holding device like a collet, 4 jaw or adjust-tru chuck. Got it?

 

[DavidR8]

Thanks @mikey, you've confirmed my thinking that he basically made a collet.
It is definitely a cool trick.
Coincidentally I just watched a This Old Tony video on chucks which helped me understand more what was going on in the Joe P. vid.
All very cool stuff on my learning path!

 

[mikey]

Here is something else to ruminate on. You'll notice that us hobby guys tend to lust after collet chucks because they are cool looking and are reputed to be accurate. They are also quick to use and can be very useful for production work. HOWEVER, for first op work, a 3 jaw is about the fastest chuck to use and will be just as accurate as a collet for first op work. For second op work, a collet chuck shines when you cannot afford to mar the finish or if the part is threaded. In these instances, the accuracy of a collet chuck will be pretty good but it will NOT be as accurate as a dialed in 4 jaw independent chuck, and you can always pad the jaws of a 4 jaw to protect the work. The downside to the 4 jaw is that it takes time to dial it in but hey, we're hobby guys and time is usually less important than accuracy.

I'm not dissing collet chucks; I own five of them, but I know when to use them and when not to. Truth be told, I could live without them but I wouldn't want to work without a good 3 and 4 jaw chuck.

 

[DavidR8]

I can definitely see the advantages of a 4-jaw chuck. More time consuming to set up as you identified but I’m not sure that time is my enemy. I’m more interested in learning good practices first.


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[Nogoingback]

I can definitely see the advantages of a 4-jaw chuck. More time consuming to set up as you identified but I’m not sure that time is my enemy. I’m more interested in learning good practices first.


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The solution in the video is interesting and clever I think, but time consuming. Switching to a 4 jaw chuck and dialing
It in would be much faster, and would result in the same (or better) TIR that he achieved. With practice, dialing in a four jaw doesn't take long.

 

[darkzero]

Here is something else to ruminate on. You'll notice that us hobby guys tend to lust after collet chucks because they are cool looking and are reputed to be accurate. They are also quick to use and can be very useful for production work. HOWEVER, for first op work, a 3 jaw is about the fastest chuck to use and will be just as accurate as a collet for first op work. For second op work, a collet chuck shines when you cannot afford to mar the finish or if the part is threaded. In these instances, the accuracy of a collet chuck will be pretty good but it will NOT be as accurate as a dialed in 4 jaw independent chuck, and you can always pad the jaws of a 4 jaw to protect the work. The downside to the 4 jaw is that it takes time to dial it in but hey, we're hobby guys and time is usually less important than accuracy.

I'm not dissing collet chucks; I own five of them, but I know when to use them and when not to. Truth be told, I could live without them but I wouldn't want to work without a good 3 and 4 jaw chuck.

Thanks for posting that. And here I thought I was an outcast or an oddball. Yes I'm a hobbyist & I got me a ER collet chuck cause "everyone was doing it". But honestly I don't really care for it, I've used my faceplate more than I have used the collet chuck & that has only been a handfull of times.

The ER chuck is slow to use which is the main reason I don't use it but there are others. I tend to remove & reinsert the work piece often and my chucks are much quicker at that, glad they repeat pretty well. Most of my work aren't nominal sizes either. I suppose if I didn't have the 6-jaw chuck which is considered a second op chuck I'd probably find myself using a collet chuck more. But the collet chuck sure is great when you don't feel like risking busting your knuckles when working on something close up.

I do miss using a 5C collet closer though & I would like to have one but I don't want to invest in that many collets.

 

[dbb-the-bruce]

At the very beginning there is a text warning on the video that says "never run an empty chuck" - while this is something I wouldn't be inclined to do, I have on occasion done it (wood turning and metal turning). What's the thinking on why this is a no-no?

I could see maybe a jaw might not be engaged with the scroll, but that's not really an empty chuck problem, it's a jaws are too far out of the body problem.

Thoughts?

 

[just old al]

At the very beginning there is a text warning on the video that says "never run an empty chuck" - while this is something I wouldn't be inclined to do, I have on occasion done it (wood turning and metal turning). What's the thinking on why this is a no-no?

Thoughts?

Doesn't make a ton of sense to me. If your chuck is so bad you're thinking it's going to fling bits about...then that's a separate problem.

The only thought I have is perhaps a 4-jaw with the jaws in an asymmetrical pattern run at high speed might cause vibration - but to me that's a DDTG (don;t do that) item.

 

[nnam]

The jaws unscrew themselves and shoot out if not tighten up

 

[dbb-the-bruce]

The jaws unscrew themselves and shoot out if not tighten up

If this is happening, I would say that your jaws and scroll or screws are too loose and you have a problem with your chuck.

All metal working chucks that I've used move smoothly and solidly, they are just not going to rattle loose.
Even the woodturning chucks I've used (always scroll chucks, usually the jaws are loose enough that they flop around if nothing is in the chuck) just wouldn't be able to rattle a jaw loose. Most have pin that prevents you from winding the jaws all the way out without removing the pin.

I could see a 4 jaw chuck being out of balance at higher speeds when the jaws are set differently, but you never run so out of balance that everything is jumping around.

I should also have said that spinning an empty chuck for any length of time is rather pointless!
Anytime I may have run an empty chuck it would have been briefly to check something else out (i.e. carriage / cross slide power feed or lead screw engagement).

Anyhow, it sounds like I haven't missed out on a major safety warning. Unlike the other day on this forum when I learned about a drill grabbing thin brass or acrylic sheets and ripping them out of a vise leading to a potential finger loosing event!

-Dave